Neuroscience Exam 1

Front 1

microscopically, the individual structural and functional unit of the nervous system is the ___________.

Back 1

neuron

Front 2

supportive elements interspersed among the neurons of the CNS are called _________________.

Back 2

glial cells

Front 3

what are the two divisions of the human nervous system?

Back 3

peripheral nervous system (PNS)
central nervous system (CNS)

Front 4

what does the CNS consist of?

Back 4

brain
spinal cord

Front 5

through which roots do sensory and motor fibers enter or exit the spinal cord?

Back 5

sensory - enter posterior (dorsal) root

motor - exit anterior (ventral) root

Front 6

what combines to form a spinal nerve?

Back 6

posterior and anterior roots of the spinal cord, making them mixed nerves (posterior = sensory; anterior = motor)

Front 7

what functions are neurons specialized to do?

Back 7

receive information
transmit electrical impulses
influence other neurons or effector tissues

Front 8

what is a perikaryon?

Back 8

neuron cell body

aka soma

Front 9

what constitutes gray matter of the CNS?

Back 9

cell bodies

Front 10

Named and usually function-specific clusters of cell bodies in the CNS are called ___________.

Back 10

nuclei (s. nucleus)

Front 11

of what does the white matter of the CNS consist?

Back 11

bundles of axons wrapped in myelin

Front 12

a sheath of insulating lipoprotein wrapped around axons is ___________.

Back 12

myelin

Front 13

what are the terminal ends of the axon of a neuron?

Back 13

synapses
motor end plate (neuromuscular junction)

Front 14

what does an electrochemical synapse consist of?

Back 14

presynaptic element
synaptic cleft
postsynaptic region

Front 15

what causes the release of neurotransmitters from a presynaptic element into a synapse?

Back 15

action potential (an electrical impulse

Front 16

where are neurotransmitters stored?

Back 16

synaptic vesicles in the presynaptic element

Front 17

what is a monosynaptic reflex arc?

Back 17

one of the simplest types of neuronal circuits, a reflex arc composed of only two neurons

Front 18

____________ are involuntary responses to a particular bit of sensory input.

Back 18

Reflexes

Front 19

what is areflexia?

Back 19

lack of a reflex

Front 20

what is hyporeflexia?

Back 20

obviously weakened reflex

Front 21

what is hyperreflexia?

Back 21

excessively active reflex

Front 22

this part of the brain is the link between the brainstem and the forebrain.

Back 22

midbrain (which is continuous with the pons)

Front 23

what are the largest and most obvious parts of the human brain?

Back 23

cerebral hemispheres

Front 24

the ________________________ is a layer of neuronal cell bodies that covers the entire surface of a hemisphere.

Back 24

cerebral cortex

Front 25

what are gyri?

Back 25

elevations (hills) in the cerebral cortex

Front 26

what are sulci?

Back 26

creases (valleys) in the cerebral cortex

Front 27

this is also called the basal ganglia.

Back 27

basal nuclei

(prominent group of neuronal cell bodies)

Front 28

A ______________________________ is a set of neurons linked together to convey a particular block of information or accomplish a particular task.

Back 28

functional system

Front 29

anatomic parts of the CNS, such as the medulla and pons, are commonly called __________.

Back 29

regions

Front 30

the study of the structure and function of anatomic regions of the CNS is called __________________________.

Back 30

regional neurobiology

Front 31

it is important to remember that the functional characteristics of regions coexist with those of ____________.

Back 31

systems

Front 32

what are corticospinal fibers?

Back 32

fibers with their cell bodies in the cerebral cortex and their axons end in the spinal cord

Front 33

successful diagnosis of patients with neurologic disorders will depend on, among other things, a good understanding of both ___________ and ____________ neurobiology.

Back 33

regional

systems

Front 34

in general, cranial nerve signs are more helpful than long-tract signs in ____________________________.

Back 34

localizing the lesion

Front 35

what are the combinations of neurologic deficits which may indicate involvement of one of three general locations of the CNS?

Back 35

deficits located on the same side of the head and body - indicates lesions in the cerebral hemishphere

deficits on one side of the headand on the opposite side of the body - indicates a lesion in the brain stem

deficits of the body only usually suggest a lesion in the spinal cord

Front 36

what are crossed (alternating) deficits?

Back 36

deficits on one side of the head and on the opposite side of the body

Front 37

which root of a spinal cord is afferent?

Back 37

posterior root

(conducts impulses toward the spinal cord)

Front 38

which root of a spinal cord is efferent?

Back 38

anterior root

(conducts impulses away from the spinal cord)

Front 39

the __________ is rostral to the pons but caudal to the thalamus.

Back 39

midbrain

Front 40

what is a symptom?

Back 40

departure from any normal state of structure or function that is experienced by the patient

(something is wrong and the patient knows it)

Front 41

what is a sign?

Back 41

departure from any normal state of structure or function that is discovered, observed and evaluated by a health care professional upon examining the patient

Front 42

is a sign or a symptom subjective?

Back 42

symptom

Front 43

is a sign or a symptom objective?

Back 43

sign

Front 44

the most routinely used methods to image the brain and the skull are _____________________ and _____________________________

Back 44

computed tomography (CT)
magnetic resonance imaging (MRI)

Front 45

____________________ is particularly useful in visualizing the skull and the brain in the early stages of subarachnoid hemorrhage

Back 45

CT

Front 46

what are the weighting techniques for use in MRI studies?

Back 46

T1-weighted
T2- weighted

Front 47

_______________________ visualizes arteries and veins by measuring the velocity of flow in them.

Back 47

magnetic resonance angiography (MRA)

Front 48

________ shows brain anatomy in elegant detail, cisternal relationships, cranial nerves and a wide variety of clinical abnormalities.

Back 48

MRI

Front 49

what is computed tomography?

Back 49

an x-ray imaging technique that measures the effects of tissue density and various types of atoms in the tissue on x-rays passing through that tissue

Front 50

the higher the _______________, the greater the ability of the atom to attenuate x-rays.

Back 50

atomic number

Front 51

what quality of atoms is directly related to the ability of the atom to stop x-rays?

Back 51

atomic number

the higher the atomic number of the atom, the better it can stop x-rays

Front 52

what are Hounsfield units?

Back 52

aka CT numbers

the unit used to represent the intensity of x-rays that is transmitted through tissues being measured

arbitrary system where bone is +1000 (bright white), air is -1000 (very black), and water is 0

Front 53

what are the approximate intensities of blood, brain, and CSF using the Hounsfield scale?

Back 53

blood - +100
brain - +30
CSF - +5

Front 54

present-generation CT scanners are known as _______________________ scanners.

Back 54

helical (spiral)

Front 55

_________ is a fast and accurate method of detecting recent subarachnoid hemorrhage.

Back 55

CT

Front 56

an acute subarachnoid hemorrhage in a noncontrast CT scan appears ______________ in contrast to the subarachnoid spaces and cisterns, which normally are ________________.

Back 56

hemorrhage - hyperdense (white)

spaces and cisterns - hypodense (dark)

Front 57

Enhanced CT is a technique using an ________________________ material injected intravenously followed by CT examination.

Back 57

iodinated contrast

Front 58

what is the "resonance" in magnetic resonance imaging (MRI)?

Back 58

only a pulse of radio waves at a frequency matching the angulated, spining proton will be absorbed by the proton and knock it off of its axis

Front 59

what is "relaxation" in MRI?

Back 59

when the radio wave pulse is turned off, protons off their axis will slowly return to their original axis

Front 60

the contrast material used for enhancing tumors and blood vessels is the paramagnetic rare earth ____________.

Back 60

gadolinium

Front 61

what imaging technique images acute subarrachnoid hemorrhages poorly? which imaging technique images them well?

Back 61

poorly by T1-weighted MRI

well by CT

Front 62

what are the contraindications to MRI?

Back 62

cardiac pacemakers
cochlear implants
ferromagnetic foreign bodies in the eye
certain aneurism clips

large metallic implants or ferromagnetic foreign bodies in the body may heat up

Front 63

___________ imaging planes are oriented perpendicular to the rostrocaudal axis of the forebrain, but are nearly parallel to the rostrocaudal axis of the brainstem and spinal cord.

Back 63

coronal

Front 64

_____________ images are oriented parallel to the rostrocaudal axis of the cerebral hemispheres but nearly perpendicular to the long axis of the brainstem and spinal cord

Back 64

axial

Front 65

_____________ images are at, or parallel with, the midsagittal plane of the brain or spinal cord

Back 65

sagittal

Front 66

how are coronal scans viewed?

Back 66

as though you are looking the patient in the face

Front 67

how are axial scans viewed?

Back 67

as though you are standing at the patient's feet, with the patient lying supine in the machine

Front 68

in both coronal and axial views, the patient's left side is to the observer's _________.

Back 68

right

Front 69

the number of cells in the adult human central nervous system has been estimated at _________________.

Back 69

100 billion

Front 70

what three activities, in addition to maintaining metabolism, are neurons responsible for?

Back 70

1. receive information from the environment or other nerve cells

2. process information

3. send information to other neurons or effector tissues

Front 71

what is the primary function of glia?

Back 71

to control the environment within the CNS

Front 72

what actions are glial cells responsible for?

Back 72

shuttle nutritive molecules from blood vessels to neurons

remove waste products

maintain the electrochemical surroundings of neurons

guide developing neurons to correct locations

structural support for nerve cells

Front 73

what does an archetypical neuron consist of?

Back 73

cell body (soma)
dendrites
axon

Front 74

what type of neurons have several dendrites extending from the cell body?

Back 74

multipolar neurons

Front 75

what is a terminal arbor?

Back 75

the distal end of an axon

the almost exclusive site of branching of an axon

Front 76

what is a synapse?

Back 76

contact between two neurons or between a neuron and an effector tissue which transfers signals from one to the other

Front 77

what are dendritic spines?

Back 77

small bud-like extensions of a variety of shapes frequently seen on the more distal branches of dendritic tree

Front 78

what are the only organelles seen in thin, distal dendritic branches of neurons? what is also in thicker branches?

Back 78

cytoskeletal elements (microtubules and neurofilaments

in thicker branches, you can also find mitochondria

Front 79

what is the type of intermediate filament that occurs only in neurons?

Back 79

neurofilaments

Front 80

in many nerve cells the distal dendrites collect into large, trunk-like __________________ that contain the same organelles as the cell body.

Back 80

primary dendrites

Front 81

the _____________ is the metabolic center of the nerve cell.

Back 81

perikaryon (cell body, soma)

Front 82

what is abundant in the cytoplasm of neurons?

Back 82

ribosomes
rough endoplasmic reticulum
golgi complex

Front 83

extensive, stacked layers of rER are seen as patches of basophilic staining in histologic preparations and are known as ________________.

Back 83

Nissl substance

Front 84

_____________ neurons account for more than 99% of all neuons.

Back 84

multipolar

Front 85

what is the shape of pseudounipolar or unipolar neurons?

Back 85

spherical cell body with a centrally placed nucleus

emits a single process that courses a short distance before dividing into two branches

Front 86

where are the cell bodies of pseudounipolar axons usually found?

Back 86

sensory ganglia of cranial and spinal nerves

Front 87

what is the shape of bipolar neurons?

Back 87

round or oval perikaryon, with a single large process emanating from each end

Front 88

where are bipolar neurons commonly found?

Back 88

structures associated with special senses (retina, nose, vestibular and auditory systems)

Front 89

the axon arises from the cell body at a small elevation called the __________________.

Back 89

axon hillock

Front 90

the proximal part of the axon, adjacent to the axon hillock, is the ______________________

Back 90

initial segment

Front 91

what features can distinguish axons from dendrites at the ultrastructural level?

Back 91

axons are typically devoid of ribosomes, whereas dendrites have ribosomes

axons can extend for long distances before branching and terminating

Front 92

to what does the term nerve fiber refer?

Back 92

axon and the sheath (myelination) that is provided by support cells

Front 93

in most neurons, each axon terminal is capped with small ___________________

Back 93

terminal boutons

Front 94

in some cells, boutons are found along the length of the axon, where they are called __________________.

Back 94

boutons en passant

Front 95

the site at which an axon terminal communicates with a second neuron, or with an effector tissue, is called a ___________.

Back 95

synapse

Front 96

axonal transport from the cell body toward the terminals is called _____________________ transport

Back 96

anterograde (orthograde)

Front 97

axonal transport from the terminals toward the cell body is called ________________ transport.

Back 97

retrograde

Front 98

what are the two classifications of anterograde axonal transport?

Back 98

fast (400 mm/day)

slow (~1 mm/day)

Front 99

what protein is the basis for fast anterograde axonal transport?

Back 99

kinesin

an ATPase which moves macromolecule-containing vesicles and mitochondria along microtubules

Front 100

what is carried by slow anterograde axonal transport?

Back 100

important structural and metabolic components from the cell body to axon terminals

Front 101

what is carried by fast anterograde axonal transport?

Back 101

macromolecule-containing vesicles and mitochondria

Front 102

______________________ allows the neuron to respond to molecules, for example, growth factors, which are taken up near the axon terminal by either pinocytosis or receptor-mediated endocytosis.

Back 102

retrograde axonal transport

also functions in the continual recycling of components of the axon terminal

Front 103

what protein drives retrograde axonal transport?

Back 103

dynein

Front 104

how is axonal transport important in rabies?

Back 104

rabies virus replicates in muscle tissue at the site of a bite by a rabid animal and is then transported in a retrograde direction to the cell bodies of neurons which synapse on that muscle

Front 105

how is axonal transport important in tetanus?

Back 105

clostridium tetani, a bacterium, replicates in muscle tissue and the toxin it produces is carried in a retrograde direction to the cell bodies of neurons which innervate the muscle

Front 106

In the CNS, a cluster of functionally related nerve cell bodies is most commonly called a ______________

Back 106

nucleus

Front 107

cell bodies in the CNS that are arranged in a layer may be called a ____________________.

Back 107

layer, lamina or stratum

Front 108

columnar groups of cell bodies in the CNS may be called _____________.

Back 108

columns

Front 109

where are columns found in the CNS?

Back 109

group of cell bodies arranged in a column

found in cerebral cortex (group of cells that are related by fcn and by location of stimulus that drives them) or spinal cord (longitudinal group of functionally related cells that extend for part or all of the length of the brainstem or spinal cord)

Front 110

bundles of axons in the CNS are called __________________________.

Back 110

tracts, fasciculi or leminisci

typically composed of specific populations of functionally related fibers

Front 111

a group of several tracts or fasciculi is called a _________________.

Back 111

funiculus

(in certain cases, a system)

Front 112

in the PNS, collections of cell bodies form a _______________.

Back 112

ganglion

could be sensory or motor

Front 113

in the PNS, axons make up _____________________.

Back 113

nerves, rami, or roots

Front 114

a neuron that conducts signals from the periphery toward the CNS is called ______________

Back 114

afferent

Front 115

a neuron that conducts signals from the CNS toward the periphery is called ______________

Back 115

efferent

Front 116

neurons with long axons that convey signals to a distant target are called ________________________

Back 116

projection neurons

Front 117

neurons that act locally (because dendrites and axon are limited to the vicinity of the cell body) are called _________________

Back 117

interneurons (local circuit cells

Front 118

what are dopaminergic neurons?

Back 118

neurons that produce dopamine

Front 119

what are glutamergic neurons?

Back 119

neurons that produce glutamate

neurons whose axons form the corticospinal tracts

Front 120

peptidergic

Back 120

contain peptides such as substance P

Front 121

the communicative function of neurons is carried out by fluctuations in their _____________________

Back 121

electrical potential

Front 122

neurons carry a ______________ electrical charge compared to the ECF bathing them

Back 122

negative

Front 123

the plasma membrane is referred to as ______________ because certain ions can cross at certain times but there is not a free exchange

Back 123

semi-permeable

Front 124

by what methods can specific ion channels be opened and closed?

Back 124

chemical signals (neurotransmitters)
mechanical distortion of membrane
voltage changes

Front 125

neurons that receive information from the environment are called ______________________________

Back 125

primary sensory neurons

Front 126

list some examples of primary sensory neurons

Back 126

photoreceptors
chemoreceptors
mechanoreceptors
thermoreceptors
nociceptors

Front 127

a graded depolarizing potential in a primary sensory neuron as the result of a stimulus is called a ______________________

Back 127

generator potential

Front 128

the process of converting sensory input into a form interpretable by the nervous system is ___________

Back 128

transduction

Front 129

how do rod and cone photoreceptors of the retina transduce light energy?

Back 129

photon strikes photoreceptor
many sodium channels close
photoreceptor hyperpolarizes

Front 130

what makes photoreceptors unique among sensory cells?

Back 130

become more negative (hyperpolarized) upon application of a stimulus, rather than more positive (depolarized)

Front 131

how do taste and olfactory receptor cells mediate the two primary types of chemoreception?

Back 131

both respond to the presence of specific chemicals dissolved in a solution

Front 132

______________ transduce various qualities of physical force into electrical signals that are transmitted by sensory neurons

Back 132

mechanoreceptors

e.g. vestibular, auditory, and somatosensory systems

Front 133

____________ transduce noxious (painful) stimuli

Back 133

nociceptors

Front 134

___________ transduce temperature changes in skin and viscera

Back 134

thermoreceptors

Front 135

what are the two broad types of synapses?

Back 135

electrical
chemical (far more common, esp. in CNS)

Front 136

the prominent collection of vesicles in the presynaptic element of a synapse contain __________________

Back 136

neurotransmitter (to be released into the synaptic cleft)

Front 137

what supplies the energy for synaptic function?

Back 137

mitochondria gathered in the terminal axonal bouton

Front 138

what are the two important functional properties of chemical synapses?

Back 138

unidirectional

strength of effect on postsynaptic membrane is variable and partly dependent on amount of neurotransmitter released

Front 139

each synaptic vesicle contains a fixed amount of neurotransmitter called a ______________

Back 139

quantum

Front 140

biogenic amines

Back 140

class of neurotransmitters

includes acetylcholine, dopamine, and norepinephrine

Front 141

amino acids

Back 141

class of neurotransmitters

includes glutamate and GABA

Front 142

nucleotides

Back 142

class of neurotransmitters

includes adenosine

Front 143

neuropeptides

Back 143

class of neurotransmitters

includes substance P, cholecystokinin, and somatostatin

Front 144

gases (NT)

Back 144

class of neurotransmitters

includes nitric oxide and carbon monoxide

Front 145

biogenic amines and amino acid neurotransmitters are synthesized in the ______________________, though the required enzymes are made in the _________________

Back 145

axon terminal

cell body

Front 146

_______________________ affects dopamine-synthesizing neurons located in an area of the brain stem known as substantia nigra (these cells die at an accelerated rate)

Back 146

parkinson's disease

Front 147

_____________________ affects several million Americans and appears to be caused by imbalances in the phosphatidyl inositol-linked neurotransmitter system

Back 147

bipolar disorder

Front 148

the drug _____________________ stabilizes phosphatidyl inositol (PI) turnover, stabilizing the mood of a patient with bipolar disorder

Back 148

lithium carbonate

Front 149

__________________ is characterized by the degeneration of neurons in basal forebrain nuclei, the loss of synapses in the cerebral cortex and hippocampus, and the presence of pathologic structures called neurofibrillary tangles and senile plaques

Back 149

alzheimer disease

Front 150

what pathologic structures are characteristic of alzheimer patients?

Back 150

fibrillary tangles
senile plaques

Front 151

in ______________________, the patient's immune system produces antibodies to the nicotinic acetylcholine receptor

Back 151

myasthenia gravis

Front 152

the ____________________________ is a ligand-gated channel found at the synapse between primary motor neuron and skeletal muscle fibers

Back 152

nicotinic acetylcholine receptor

Front 153

astrocytes modulate synaptic activity in their vicinity by releasing small amounts of ___________

Back 153

glutamate

Front 154

astrocytes are derived from _____________

Back 154

neuroectoderm

Front 155

oligodendrocytes are derived from _____________

Back 155

neuroectoderm

Front 156

microglia are derived from ______________

Back 156

mesoderm

Front 157

what cells of the PNS are analogous to the astrocytes, oligodendrocytes, and microglia?

Back 157

satellite cells
Schwann cells
macrophages

Front 158

where are astrocytes found?

Back 158

throughout the CNS

Front 159

how do astrocytes appear?

Back 159

highly branched cells with processes that contact most of the surfaces of neuronal dendrites and cell bodies, as well as some axonal surfaces; other processes end in end feet

Front 160

_______________ are terminal expansions of astrocyte processes which join together to completely line the interfaces between the CNS and other tissues

Back 160

end feet

Front 161

the outer surface of the brain and spinal cord, where it meets the inner surface of the pia mater is covered with a coating of several layers of joined end-feet called the __________________

Back 161

glia limitans (glial limiting membrane)

Front 162

the _________________ is the innermost of the meningeal membranes that enclose the CNS

Back 162

pia mater

Front 163

astrocytes of gray matter are called _______________

astrocytes of white matter are called _______________

Back 163

protoplasmic astrocytes

fibrous astrocytes

Front 164

astrocytes of white matter are called fibrous astrocytes because they have a high content of _________________

Back 164

intermediate filaments

Front 165

astrocytes can be distinguished immunohistochemically by the presence of intermediate filaments with a distinctive marker protein called _______________________

Back 165

glial fibrillary acidic protein (GFAP)

Front 166

__________________ content of protoplasmic astrocytes increases in pathologic conditions

Back 166

glial fibrillary acidic protein (GFAP)

Front 167

astrocytes, in the form of __________________, provide a pathway for neuronal migration during development

Back 167

radial glial cells

Front 168

what do astrocytes do in the adult brain?

Back 168

frame certain clusters of neurons

enclose bundles of unmyelinated axons in white matter

Front 169

if injury to the CNS results in the destruction of cells, the space created by the breakdown of debris is filled by proliferation or hypertrophy of ____________; this results in the formation of an __________________

Back 169

astrocytes

astrocytic scar

Front 170

the majority of CNS tumors are of ________________ origin.

Back 170

astrocytic

astrocytes maintain the ability to proliferate in the mature brain, making them susceptible to events that disrupt the control of cell division

Front 171

astrocytes secrete ________________ vital to normal function of some neurons

Back 171

growth factors

Front 172

astrocytes secrete _____________________________ necessary for synaptic growth and plasticity

Back 172

cholesterol and lipoproteins

Front 173

how do astrocytes contribute to the regulation of inflammatory processes in the CNS?

Back 173

secrete cytokines and immune mediators such as IL-1, IL-6 and prostaglandin in disease processes

Front 174

astrocytes buffer the _________________ and _________________ of extracellular fluid

Back 174

ionic composition

pH

Front 175

astrocytes participate in ______________ metabolism as well as modulation of synaptic transmission by releasing small amounts of _________________

Back 175

neurotransmitter

glutamate

Front 176

how are astrocyte tumors of specific types distributed in the CNS?

Back 176

have characteristic distributions rather than random distribution

ex. glioblastoma multiforme is most frequently in frontal or temporal lobe

Front 177

in the CNS, vessels are induced by the surrounding jacket of _________________ to form extensive tight junctions

Back 177

astrocyte end-feet

keeps solutes from reaching the neuroal tissue unless they pass through the endothelial cells

(i.e. blood-brain barrier)

Front 178

what can diffuse freely across the endothelial cells of the blood brain barrier?

Back 178

water
gases
lipid-soluble small molecules

others must be carried across by transport systems (highly selective exchange)

Front 179

why is the blood-brain barrier of major clinical importance?

Back 179

largely excludes many drugs from the CNS

Front 180

in what type of brain matter are oligodendrocytes found?

Back 180

gray matter
white matter

Front 181

the function of oligodendrocytes is __________________

Back 181

myelination

(provision of an electrochemically insulating sheath around all but the smalles axons in white matter)

Front 182

where is the cytoplasm of an oligodendrocyte after it has myelinated an axon?

Back 182

only found in the innermost and outermost turns

Front 183

a myelinated axon of the CNS is covered by a series of myelin segments, each formed by an ____________________

Back 183

oligodendroglial cell (oligodendrocyte)

Front 184

interruptions between myelin segments on an axon are called ____________________

Back 184

nodes of ranvier

Front 185

morphologic specializations at the nodes of Ranvier include ____________________________________________

Back 185

dense undercoating of axonal membrane

contact by an astrocyte process

Front 186

________________________ arise from the cells that make up the structure of the brain and spinal cord, as well as its coverings

Back 186

primary brain tumors

Front 187

_____________ are the glial cell tumors encountered most often

Back 187

astrocytomas

Front 188

how are astrocytomas traditionally evaluated?

Back 188

how closely the neoplastic cells resemble non-neoplastic astrocytes (a grading system which attempts to define the aggressiveness of the tumor and to give a prognosis)

Front 189

grade I astrocytomas

Back 189

uncommon
resemble differentiated astrocytes
react to an injury within the brain
usually from fibrillary astrocytes in the white matter (many stubby processes)
grow slowly (gradual enlargement is main clue that it exists)

Front 190

grade II astrocytomas

Back 190

prominent processes filled with glial filaments (infiltrate between myelinated axons)

commonly found in adults

years may elapse before symptoms present

become more aggressive if they recur after surgery

Front 191

which grades of astrocytomas are generally slowly growing?

Back 191

grade I
grade II

Front 192

grade III astrocytomas

Back 192

nuclei are often enlarged (with increased density of chromatin)

lose uniformity of nuclear appearance

mitotic figures (chromosomes on spindles) frequently noted

density of blood vessels is increased

rapidly growing (dividing) and malignant

Front 193

grade IV astrocytomas

Back 193

highly malignant

astrocytes are spindled

elongated nuclei may have many mitotic figures

can invade letomeninges, spreading from one gyrus to the next

spreads between hemispheres, marching through the corpus callosum

Front 194

what is another name for glioblastoma multiforme?

Back 194

grade IV astrocytoma

Front 195

what are the intrinsic features of glioblastoma multiforme?

Back 195

complex neovascular structure

sharp borders between living and dead tumor tissue

Front 196

what is the most common astrocytoma encountered in middle-aged and elderly adult patients?

Back 196

glioblastoma multiforme

(grade IV astrocytoma)

Front 197

what is the survival time of patients with a grade 4 astrocytoma, once diagnosed?

Back 197

as little as only weeks

Front 198

oligodendroglia can produce slow-growing tumors, located ______________________ rather than in the diencephalon or in the basal ganglia

Back 198

lobes of the brain

Front 199

how do oligodendroglia in oligodendrogliomas (tumors of the brain lobes) appear?

Back 199

dark, round nuclei centered within clear cytoplasm (yold of a fried egg embedded in egg white

Front 200

the ventricular spaces of the brain and the central canal of the spinal cord are lined by an epithelium of _______________________

Back 200

ependymal cells

Front 201

tumors of ependymal cells are called ______________________

Back 201

ependymomas

Front 202

when ependymomas are found in children or adolescents, they are found ___________________

Back 202

in the fourth ventricle

Front 203

when ependymomas are found in adults, they are found ___________________

Back 203

in the spinal cord

(esp. cervical level)

Front 204

ependymomas are more/less infiltrative than astrocytomas?

Back 204

less

Front 205

why can ependymomas be more easily dissected away from spinal tissues and removed by a neurosurgeon

Back 205

they are more circumscribed

(confined to a limited area)

Front 206

how are tumors derived from microglia interpreted?

Back 206

as lymphomas (large family of neoplasms consisting of bone marrow-derived or thymus-derived cells, B cells or T cells respectively)

Front 207

lymphomas of the brain are more frequent in patients who suffer from one of the various states of __________________________

Back 207

acquired immunodeficiency

(HIV or medicine-induced immunodeficiency)

Front 208

tumors that primarily affect children may contain cells that function like ________________

Back 208

stem cells

Front 209

medulloblastomas arise in the _____________________ of children and consist of primitive "___________" that are capable of developing along several pathways

Back 209

cerebellar hemispheres

blue cells

Front 210

why must medulloblastomas be treated aggressively?

Back 210

most retain the characteristic unrestrained growth of embryonal cells without differentiation, so they quickly spread along the surface of the brain and spinal cord

Front 211

benign primary brain tumors are often covered by a ____________________ that demarcates them from surrounding normal brain

Back 211

fibrous, vascularized capsule

Front 212

how do benign primary brain tumors cause problems?

Back 212

they compress normal tissue as they grow

Front 213

tumors that primarily affect children may contain cells that function like ________________

Back 213

stem cells

Front 214

medulloblastomas arise in the _____________________ of children and consist of primitive "___________" that are capable of developing along several pathways

Back 214

cerebellar hemispheres

blue cells

Front 215

why must medulloblastomas be treated aggressively?

Back 215

most retain the characteristic unrestrained growth of embryonal cells without differentiation, so they quickly spread along the surface of the brain and spinal cord

Front 216

benign primary brain tumors are often covered by a ____________________ that demarcates them from surrounding normal brain

Back 216

fibrous, vascularized capsule

Front 217

how do benign primary brain tumors cause problems?

Back 217

they compress normal tissue as they grow

Front 218

what are the two types of frequently encountered benign primary brain tumors?

Back 218

meningioma

schwannoma

Front 219

from where do metastatic brain tumors arise?

Back 219

malignant cells that originate outside the nervous system

Front 220

how do the growth patterns of metastatic tumors differ from primary tumors?

Back 220

clumps of tumor cells, broken away from a tumor, travel through the bloodstream and become lodged at tiny arteriolar branch points (often at gray/white matter junction)

Front 221

___________________ is the most common primary tumor to secondarily involve the brain.

Back 221

lung carcinoma

Front 222

breast carcinoma can spread to the _____________ or the _____________

Back 222

dura

brain substance

Front 223

prostate carcinoma can spread to the ______________

Back 223

spinal cord

(travels through veins of Batson's venous plexus)

Front 224

what are the PNS supporting cells? what are they analogous to from the CNS?

Back 224

satellite cells - astrocytes

schwann cells - oligodendrocytes

Front 225

______________ surround the cell bodies of neurons in sensory and autonomic ganglia

Back 225

satellite cells

Front 226

_____________ ensheath the axons in peripheral nerves

Back 226

schwann cells

Front 227

small pockets of cytoplasm, known as ____________________________ are found at irregular intervals in PNS myelin

Back 227

Schmidt-Lanterman clefts

Front 228

A ________________ covers the external surface of a schwann cell

Back 228

basal lamina

formed by the schwann cell
may help stabilize during myelin formation

Front 229

each schwann cell can myelinate how many internodes of a PNS axon?

Back 229

only a single internode

(oligodendrocytes in the CNS can myelinate multiple internodes)

Front 230

in what are unmyelinated axons in the PNS enclosed?

Back 230

invaginations in Schwann cells

Front 231

what are the three connective tissue sheaths that cover peripheral nerve fibers external to the schwann cell basal lamina?

Back 231

endoneurium - innermost (type III collagen fibrils with occasional fibroblasts) - around individual axons

perineurium - middle sheath (several concentric layers of flattened fibroblasts with basal laminae) - around groups (fascicles) of axons

epineurium - outermost (dense connective tissue sheath of type I collagen and typical fibroblasts) - surrounds entire nerve

Front 232

what forms the blood-nerve barrier?

Back 232

tight junctions connecting perineurial cells

Front 233

why are schwannomas easily excised?

Back 233

they arise singly
they are encapsulated
they do not include nerve fibers

Front 234

why are neurofibromas difficult to remove?

Back 234

they arise in multiples
they are not encapsulated
they infiltrate nerve bundles

Front 235

how can neurons recover from damage?

Back 235

only if axons are injured

if cell body is damaged, axon cannot be regenerated

Front 236

what type of axonal injuries have a better prognosis for regeneration?

Back 236

compression or crushing

severing has low success for regeneration

Front 237

in milder lesions in which focal demyelination occurs without axonal degeneration (___________), there is loss of conduction in the nerve, but recovery is to be expected

Back 237

neurapraxia

Front 238

when compression or crushing kills the axons distal to the site of injury, the neuronal cell bodies, which are in the ___________ or __________ usually survive

Back 238

spinal cord

sensory or autonomic ganglia

Front 239

cell bodies of damaged neurons may undergo _______________ in response to the trauma

Back 239

chromatolysis

Front 240

days to weeks after the trauma ____________ starts at the point of injury, and the _______ grow distally

Back 240

axonal sprouting

axons

Front 241

while axonal sprouting occurs, axons die and are removed by macrophages in the distal part of the nerve, what remains?

Back 241

schwann cells, which lose their myelin but keep their basal lamina

Front 242

what are bands of Bungner?

Back 242

cordons of Schwann cells which have proliferated inside the basal lamina after an injury to the axon

Front 243

________________ and ________________ guide distally growing axonal sprouts after injury

Back 243

schwann cells

basal lamina

Front 244

macrophages, activated by phagocytosis of myelin debris, signal schwann cells to secrete ________________, a neurotrophin that promotes axon growth

Back 244

nerve growth factor

Front 245

the growth rate of sprouting axons is about ____________

Back 245

1mm/day

Front 246

in a compression injury (___________), the proximal axon sprouts and distal bands of Schwann cells remain in their original orientation, so nerve fibers are lined up just as they were before the injury

Back 246

axonotmesis

Front 247

when a peripheral nerve is severed (_____________) regeneration is less likely to occur

Back 247

neurotmesis

Front 248

why is regeneration so unlikely in a severed peripheral nerve?

Back 248

sprouting occurs at the proximal end of the axon an, and the axon grows, but it may not reach its distal target

Front 249

some regenerating axons enter correct bands of bungner (regain fcn), some enter wrong bands of bungner (don't regain fcn), and others fail to enter schwann cell tubes, ending blindly in connective tissue as _______________

Back 249

neuromas

Front 250

mechanical or chemical stimulation of _____________ may be the cause of "phantom pain" in persons with amputated limbs

Back 250

neuromas (blindly ending sensory axons)

Front 251

what happens in response to neuronal injury in the CNS?

Back 251

neuron mounts a sprouting response

astrocytes hypertrophy and proliferate, filling space left by injury or by degeneration of damaged nerve tissue (form a scar)

sprouts can't get through scar

axonal sprouts are retracted and loss of function is permanent

Front 252

what factors can inhibit the regrowth of axons in the CNS?

Back 252

astrocyte scar

astrocytes don't secete adequate growth factors to sustain regrowing axons

molecules in oligodendrocyte myelin

Front 253

from what germ layer does the central nervous system develop?

Back 253

primitive ectoderm

Front 254

how much does the brain weigh at birth? at 6 years? in adulthood?

Back 254

birth - 800 g
6 yo - 1200 g
adult - 1400 g

Front 255

most, but not all neurons undergo their last cell division ________________

Back 255

before birth

Front 256

what percent of births are associated with major malformations of the CNS?

Back 256

3 %

Front 257

about ___% of spontaneously aborted fetuses and __% of infants who die within the first year of life have major CNS malformations

Back 257

75

40

Front 258

the basic form of the human CNS is complete by about ________________

Back 258

the sixth week of gestation

Front 259

phases after the basic form of the CNS, cellular proliferation and migration, are most prominent ______________________

Back 259

in the second trimester of gestation

(though they continue until term)

Front 260

myelination peaks _________________ but continues into adulthood

Back 260

in the third trimester

Front 261

the development of synaptic connections between neurons and the response of the brain to its experiences result in its ______________

Back 261

functional maturity

(process that continues throughout life)

Front 262

one of the first indicators of the developing nervous system to appear is the ________________ on the posterior aspect of the trilaminar embryo

Back 262

neural groove

Front 263

the neural groove deepens and the _____________ at the lateral margins of the ________________ become obvious as they elevate and eventually join along the posterior midline to form the ______________________

Back 263

neural folds

neural plate

neural tube

Front 264

the apposition and fusion of the neural folds and of the overlying ectoderm initially takes place at what will be the ________________ of the spinal cord, then proceeds _____________ from this location

Back 264

cervical levels

rostrally and caudally

Front 265

the _______________________ are the last points at which the neural tube closes

Back 265

anterior and posterior neuropores

Front 266

after formation of the neural tube, three layers appear in rapid succession. they are:

Back 266

ventricular zone
marginal zone
intermediate zone

Front 267

in early stages the closing neural plate and and tube consist of a single layer, the _________________, composed of a pseudostratified layer of fusiform-shaped cells undergoing DNA replication and cell division

Back 267

ventricular zone

Front 268

the progenitor cells of the __________________ will give rise to the neurons and some glial cells o the mature nervous system, and to the ependymal cells lining the ventricles

Back 268

ventricular zone

Front 269

immediately after the ventricular zone is formed, the ______________ appears

Back 269

marginal zone

Front 270

the ___________________ is at the abluminal aspect of the neural tube and consists of the processes of cells located within the ventricular zone, but does not contain their nuclei

Back 270

marginal zone

Front 271

the marginal zone contains ____________ cell bodies

Back 271

almost no

it will be invaded by axons of neurons that are located in the intermediate zone

Front 272

the third area of the neural tube to appear is the ____________________

Back 272

intermediate zone

Front 273

the ___________________________ is formed between the ventricular zone and the marginal zone

Back 273

intermediate zone

Front 274

the progenitor cells from the ventricular zone give rise to immature __________________

Back 274

postmitotic neurons

Front 275

immature neurons from the intermediate zone migrate to the area immediately external to the _________ zone, where they set up residence

Back 275

ventricular

Front 276

the _______________ zone develops at the interface of the ventricular and intermediate zones

Back 276

subventricular

Front 277

the progenitor cells of the subventricular zone give rise to ______________________

Back 277

macroglial cells of the CNS and to specific populations of developing neurons in the brainstem and forebrain

Front 278

development of the alar plate and the basal plate is a __________ process

Back 278

dynamic

Front 279

alar and basal plates consist of the ____________ zone and adjacent ______________ zone

Back 279

ventricular

intermediate

alar plate is posterior, whereas basal plate is anterior

Front 280

what is the basic organizational plan from which the brain and spinal cord will arise? what modification accommodates the cerebral cortex?

Back 280

appearance of the cortical plate and subplate

Front 281

the __________ forms at the interface of the marginal zone and the intermediate zone and is composed of neurons that originate from the ventricular zone

Back 281

cortical plate

Front 282

the postmitotic immature neurons of the ventricular zone, traverse the intermediate zone, using the processes of ____________ as a scaffold to take up their position as the cortical plate

Back 282

radial glia

Front 283

the __________ is a narrow region located immediately internal to the cortical plate

Back 283

subplate

Front 284

the first neural tissue appears at the end of the ___________ third week of embryonic development

Back 284

third

Front 285

a specialized part of the ectoderm, the ________________, gives rise to the brain, spinal cord and peripheral nervous system

Back 285

neuroectoderm

Front 286

the notochord arises from _______________ at about _______________

Back 286

axial mesoderm

16 days

Front 287

the notochord is completely formed by the beginning of the __________ week

Back 287

fourth

Front 288

the ___________ defines the longitudinal axis of the embryo

Back 288

notochord

Front 289

the ____________ determines the orientation of the vertebral column

Back 289

notochord

Front 290

the _____________ persists as the nucleus pulposus of the intervertebral discs

Back 290

notochord

Front 291

one important function of the ____________ is induction

Back 291

notochord

Front 292

_______________ is the directing of ectoderm overlying the notochord to form the neural plate

Back 292

induction

Front 293

associated with the process of induction is the production of ________________________ in the notochord

Back 293

cell adhesion molecules

Front 294

_________________________ diffuse from the notochord into the neural plate and function to join the primitive neuroepithelial cells into a tight unit

Back 294

cell adhesion molecules

Front 295

within the neuroectoderm, some neuroepithelial cells elongate and become spindle shaped; this is induced by the notochord and forms the ________________; it is completed by the end of the __________ week of gestation

Back 295

neural plate

third

Front 296

what are the two infolding processes that form the neural tube from the neural plate?

Back 296

primary neurulation (rostral end) - gives rise to brain and spinal cord through lumbar levels

secondary neurulation (caudal-most segment) - gives rise to sacral and coccygeal

Front 297

the neural plate begins to thicken at its lateral margins by about day __

Back 297

18 (after fertilization)

Front 298

the thickening of the lateral margins of the neural plate elevates the edges of it to form _____________

Back 298

neural folds

Front 299

the neural folds first contact each other to begin the formation of the neural tube at about day __

Back 299

20

Front 300

during the process of fusion of the neural tube, the lumen, called the _______________, is open to the amniotic cavity both rostrally and caudally

Back 300

neural canal

Front 301

the rostral opening of the neural tube is called the __________________, and closes at about day __

Back 301

anterior neuropore

24

Front 302

the caudal opening of the neural tube is called the __________________, and closes at about day __

Back 302

posterior neuropore

26
(about two days after the anterior neuropore)

Front 303

neurulation is brought about by morphologic changes in the ____________

Back 303

neuroblasts

Front 304

_____________ are the immature and dividing future neurons in the ventricular zone

Back 304

neuroblasts

Front 305

congenital malformations associated with defective neurulation are called ____________________

Back 305

dysraphic defects

Front 306

several well-controlled clinical trials have proven that supplementation with the vitamin ______________, found in green, leafy vegetables, can reduce the incidence of neural tube defects

Back 306

folic acid

Front 307

most dysraphic defects occur at the location of the ______________________

Back 307

anterior or posterior neuropore

Front 308

failure of the anterior neuropore to close results in ________________

Back 308

anencephaly

(the brain is not formed, the surrounding meninges and skull may be absent, and there are facial abnormalities

Front 309

anencephaly extends from the level of the ________________________ to the region of the __________________

Back 309

lamina terminalis

foramen magnum

Front 310

the __________________ is the site of anterior neuropore closure

Back 310

lamina terminalis

Front 311

how frequent is anencephaly?

Back 311

t of every 10,000 live births

(neonatal death is inevitable)

Front 312

an ____________________ is a herniation of intracranial contents through a defect in the cranium (__________________)

Back 312

encephalocele

crania bifidum

Front 313

a herniation of only meninges through a defect in the cranium is a _______________

Back 313

meningocele

Front 314

a herniation of meninges plus brain through a defect in the cranium is a ____________________

Back 314

meningoencephalocele

Front 315

a herniation of meninges, plus brain and a part of the ventricular system is a ___________________________

Back 315

meningohydroencephalocele

Front 316

encephaloceles are most common in the _____________ region

Back 316

occipital

(can also occur in frontal or parietal regions)

Front 317

a congenital herniation of the cerebellar vermis through the foramen magnum, which may cause pressure on the medulla oblongata and cervical spinal cord is a ____________________

Back 317

Arnold-Chiari malformation

(thought to be caused by a more subtle defect in closure of the neuropore than an encepalocele)

Front 318

________________ may go unnoticed until early adulthood and is often associated with a cavitation of the spinal cord or of the medulla

Back 318

Arnold-Chiari malformation

Front 319

a cavitation of the spinal cord is a _______________

Back 319

syringomyelia

Front 320

a cavitation of the medulla is a _______________

Back 320

syringobulbia

Front 321

defects in the closure of the posterior neuropore cause a range of malformations known collectively as _________________

Back 321

myeloschisis

(always involves a failure of of the vertebral arches at the affected levels to form completely and fuse to cover the spinal cord

Front 322

failure of the vertebral arches to form completely and to fuse to cover the spinal cord is ___________________

Back 322

spina bifida

Front 323

if the vertebral arches don't fully fuse and skin closes over it, the unseen condition is called _________________________

Back 323

spina bifida occulta

site of defect usually marked by a patch of dark, coarse hairs

Front 324

if the vertebral arches don't fully fuse and the skin doesn't close over it, leaving a patent aperture, the condition is called _______________________

Back 324

spina bifida aperta

Front 325

if a cystic mass accompanies spina bifida, the condition is called ______________________

Back 325

spina bifida cystica

Front 326

if the cyst-like structure from an incomplete fusion of the posterior neuropore contains only meninges and CSF, it is called a ______________________

Back 326

meningocele

Front 327

if the cyst-like structure from an incomplete fusion of the posterior neuropore contains meninges and CSF, plus spinal neural tissue, it is called a ______________________

Back 327

meningomyelocele

Front 328

the sacral and coccygeal segments of the spinal cord and their corresponding dorsal and ventral roots are formed by ______________________

Back 328

secondary neurulation

Front 329

secondary neurulation begins on day __ and is complete by about day __

Back 329

20

42

Front 330

a cell mass, the __________________, appears just caudal to the neural tube, enlarges and cavitates, joins the neural tube, and becomes continuous with the neural canal

Back 330

caudal eminence

Front 331

_____________________ refers to malformations of the parts of the neural tube formed by secondary neurulation

Back 331

myelodysplasia

Front 332

______________________ is a common abnormality of secondary neurulation in which the conus medullaris and filum terminale are abnormally fixed to the defective vertebral column

Back 332

tethered cord syndrome

(sustained traction damages the cord, with subsequent loss of sensations from the legs and fee, and with bladder control problems)

Front 333

the three primary brain vesicles are formed during the __ week after fertilization, in which the anterior neuropore closes and neural tissue in the cranial region grows rapidly

Back 333

fourth

Front 334

the three primary brain vesicles are the _____________, _______________, and _______________

Back 334

prosencephalon (forebrain)

mesencephalon (midbrain)

rhombencephalon (hindbrain)

Front 335

the slight bend in the developing neural tube at the rhombencephalon-spinal cord junction is the __________________

Back 335

cervical flexure

Front 336

a bend in the neural tube at the level of the mesencephalon is the _____________________

Back 336

mesencephalic (cephalic) flexure

Front 337

when do the three primary brain vesicles divide into five secondary brain vesicles

Back 337

during the fifth week

Front 338

what are the two additional flexures that arise from the division of the three primary brain vesicles?

Back 338

pontine flexure - divides hindbrain

telencephalic flexure - divides forebrain
(diencephalic-telencephalic sulcus)

Front 339

the _________________ divides the hindbrain into the myeloencephalon caudally and the metencephalon rostrally

Back 339

pontine flexure

Front 340

which primary vesicle does not partition further?

Back 340

mesencephalon (midbrain)

Front 341

the ___________________ divides the forebrain into the diencephalon caudally and the telencephalon rostrally

Back 341

telencephalonic flexure

Front 342

what is the order of brain vesicles from rostral to caudal?

Back 342

telencephalon
diencephalon
mesencephalon
metencephalon
myeloencephalon

Tel-Di-Mes-Met-Myelo

Front 343

what is the order of primary brain vesicles from rostral to caudal?

Back 343

prosencephalon
mesencephalon
rhombencephalon

Pros-Mes-Rhomb

Front 344

the ____________ (meaning end-brain) forms as an outpocketing of the forebrain and expands enormously with its complex lobes, gyri, and sulci, to become the largest part of the brain

Back 344

telencephalon

Front 345

the main structures of the forebrain develop during the _____ month of gestation

Back 345

second

Front 346

at about the end of the fifth week, the telencephalon gives rise to two lateral expansions called the ___________________

Back 346

telencephalic (cerebral) vesicles

Front 347

_______________ are the primordia of the cerebral hemispheres

Back 347

telencephalic (cerebral) vesicles

Front 348

the adult derivatives of the telencephalic vesicles are the:

Back 348

cerebral cortex
subcortical white matter (including internal capsule)
olfactory bulb
olfactory tract
portions of the basal ganglia
amygdala
hippocampus

Front 349

the ___________________ develops into the thalamic nuclei and associated structures and also gives rise to the optic cup, which eventually forms the optic nerve and retina

Back 349

diencephalon

Front 350

by __ weeks of development, the major structures of the CNS are clearly recognizable by their morphologic features

Back 350

10

Front 351

immature versions of all structures in the brain are present by the end of the __________________

Back 351

first trimester

Front 352

the sequence of events by which the primitive prosencephalon differentiates into the diencephalic and telencephalic vesicles is called _______________________

Back 352

prosencephalization

Front 353

failure of the prosencephalon to undergo cleavage results in a malformation called ______________

Back 353

holoprosencephaly

Front 354

in the most severe form of a failure of the prosencephalon to undergo cleavage no discernible lobes develop; this is called ________________

Back 354

alobar holoprosencephaly

Front 355

in _______________________, there is some separation of the forebrain into two discernible lobes (more prominent in occipital areas) and partial development of the falx cerebri

Back 355

semilobar holoprosencephaly

Front 356

_____________ is a facial malformation characterized by unusually close-set eyes

Back 356

hypotelorism

Front 357

_____________ is a facial malformation characterized by the presence of only a single, midline eye

Back 357

cyclops

Front 358

how do facial defects relate to forebrain malformations?

Back 358

the forebrain develops at about the same time as facial features, so malformations of one often lead to malformations of another

in general, the more severe the brain malformation, the more severe the facial defect

Front 359

the acronym "TORCH" is often used for the more common etiologic agents (infectious diseases) which cause congenital nervous system defects; it stands for:

Back 359

Toxoplasma
Other (syphilis)
Rubella
Cytomegalovirus
Herpes simplex virus

Front 360

nervous system defects caused by infectious diseases include:

Back 360

cataracts
retinitis
blindness
deafness
cerebral calcifications
cerebral atrophy
microcephaly

Front 361

the _________________ is an elaboration of the lumen of cephalic portions of the neural tube

Back 361

ventricular system

Front 362

the cavities of the telencephalic vesicles become the ______________________

Back 362

lateral ventricles

Front 363

the diencephalic cavity becomes the ______________________

Back 363

third ventricle

Front 364

the rhombencephalic cavity becomes the ___________________________

Back 364

fourth ventricle

Front 365

the cavity of the mesencephalon becomes the ____________________

Back 365

cerebral aqueduct (of Sylvius)

Front 366

the cerebral aqueduct (of Sylvius) connects the ________________________

Back 366

third and fourth ventricles

Front 367

the openings between the lateral ventricles and the third ventricle become the ____________________________

Back 367

intraventricular foramina (of Monro)

Front 368

the ventricular system is lined with ______________________

Back 368

ependymal cells

Front 369

in each ventricle, blood vessels invaginate the ependymal cell membrane to form the _________________

Back 369

choroid plexus

Front 370

openings that arise in the caudal roof of the fourth ventricle during development form a communication between the _____________________________________; what are these openings?

Back 370

ventricular system and the subarachnoid space

these openings are the foramen of Magendie (midline medial aperture) and the foramina of Luschka (paired lateral foramina)

Front 371

the foramen of Magendie and the foramina of Luschka form slowly, but are patent by the end of the _____________________

Back 371

first trimester

Front 372

CSF is produced mainly by the choroid plexus of the ____________________________

It escapes to the subarachnoid space through the _____________________________

Back 372

lateral and third ventricles

foramen of Magendie and foramina of Luschka (fourth ventricle)

Front 373

CSF is absorbed into the venous system through the arachnoid villi located primarily in the _______________________

Back 373

superior sagittal sinus

Front 374

the condition in which the ventricular system becomes markedly dilated because of an obstruction to the flow of CSF through the ventricles during prenatal development is called _____________________

Back 374

congenital hydrocephalus

Front 375

___________________ are seen in the Dandy-Walker malformation

Back 375

enlarged ventricles

cystic dilation of the fourth ventricle

variable degree of aplasia of the cerebellar vermis

Front 376

aplasia

Back 376

absence or defective development

Front 377

the peripheral nervous system develops mostly from cells of the ____________________

Back 377

neural crest

Front 378

specialized epidermal cells called _________________ are found in the developing head region, and join neural crest cells to form ganglia of several cranial nerves

Back 378

placodes

cranial nerves are V, VII, VIII, IX, and X

Front 379

what are the cranial nerve ganglia which arise from neural crest cells and placode cells?

Back 379

trigeminal/semilunar (V) ganglion
geniculate ganglion (VII)
superior and inferior ganglia of the glossopharyngeal nerve (IX)
jugular and nodose ganglia of vagus nerve (X)

Front 380

in the __________________________, pseudounipolar cells have failed to migrate with the neural crest and remain inside the CNS, forming a ganglion ectopically trapped inside the mesencephalon

Back 380

mesencephalic nucleus of the trigeminal nerve

Front 381

the cell bodies of the ganglia of cranial nerve VIII (the vestibulocochlear nerve) arise primarily from the ____________

Back 381

otic placode

(small contribution from neural crest)

retain a bipolar shape in the adult

Front 382

pseudounipolar cells of posterior, or dorsal, root ganglia are derived from ___________________

Back 382

neural crest

Front 383

schwann cells, which ensheathe and myelinate axons in the peripheral nervous system, are derived from _______________

Back 383

neural crest cells

Front 384

________________ migrate in a segmental fashion, accompanying the growing processes of the peripheral nerve fibers they will eventually ensheathe

Back 384

schwann cells

Front 385

in general, CNS neuroblasts arise at the ___________________ of the developing brain

Back 385

ventricular surface
(luminal surface of the neural tube)

Front 386

just after the neural tube forms, it is a _________________ epithelium

Back 386

pseudostratified columnar

Front 387

as development proceeds, the wall of the neural tube thickens and dividing cells cluster at the ventricular surface, leaving a zone without cell bodies at the abluminal surface; this region is called the _______________

Back 387

marginal zone

Front 388

as cells in the neural tube undergo their last division, they begin to migrate away from the luminal (ventricular) surface on transient glial cell guides called ______________

Back 388

radial glia

Front 389

as the neural tube cells migrate, away from the ventricular surface, they form a moving front of cell bodies between the marginal and ventricular zones called the ______________________

Back 389

intermediate zone

Front 390

after neural tube cells migrate and take up their final positions in the developing brain, they begin to extend processes and form connections with ________________________

Back 390

other neurons or muscle cells

Front 391

on developing neural tube cells, an axonal process, tipped by a spade-like extension called the _____________, begins to drive its way through intervening regions to reach distant targets

Back 391

growth cone

Front 392

although the idea is controversial, both neurons and glia seem to originate from a __________________________

Back 392

single precursor cell population

(gives rise to two separate lineages; neuroblastic and glioblastic)

Front 393

_______________ lineage generates neurons

Back 393

neuroblastic

Front 394

______________ lineage includes precursors of radial glial cells, astroglial cells, and oligodendrocytes

Back 394

glioblastic lineage

Front 395

the three main branches of the glioblastic lineage are the ____________________, the ____________________, and the ____________________

Back 395

type I astrocyte progenitor

oligodendrocyte/type II astrocyte precursor

radial glia progenitor

Front 396

whereas all other cell types persist into adulthood, radial glial cells in most regions of the brain appear to be converted to ________________________

Back 396

astrocytes
ependymal cells
tanycytes

Front 397

two notable exceptions where radial glia cells retain most of their features in adulthood are the _________________ in the cerebellum, and the _________________ in the retina

Back 397

Bergmann glial cells

Muller cells

Front 398

gray matter of the spinal cord is butterfly shaped with _______________________________ horns

Back 398

anterior (ventral)
posterior (dorsal)
lateral - at only some levels

Front 399

spinal cord develops from caudal portions of the neural tube, where the neural canal becomes ___________________________

Back 399

the central canal of the spinal cord

Front 400

neuroblasts that give rise to spinal cord neurons migrate peripherally to form four longitudinal ___________ which become the gray matter of the spinal cord

Back 400

plates

anterior two - basal plate
posterior two - alar plate

Front 401

the basal and alar plates on each side are separated by a longitudinal groove called the __________________ in the lateral wall of the central canal

Back 401

sulcus limitans

Front 402

the _________ plate develops into the anterior (ventral) horn of the spinal cord and the ____________ plate develops into the posterior (dorsal) horn.

Back 402

basal

alar

Front 403

as each somite develops, it subdivides into a _____________, a _______________, and a _______________

Back 403

sclerotome - forms vertebrae
dermatome - forms skin and dermis
myotome - forms muscles

Front 404

the posterior (sensory) and anterior (motor) roots of the spinal cord join at about the level of the future _________________ to form the _________________

Back 404

intervertebral foramina

spinal nerves

Front 405

vertebrae develop between the spinal nerves and are thus __________________ in position, even though they originate from the segmental sclerotomes

Back 405

intersegmental

Front 406

by the end of the _________________ the spinal cord, its meningeal coverings, and the surrounding vertebral arches are fully formed

Back 406

first trimester

Front 407

why is the spinal cord shorter than the vertebral column?

Back 407

the vertebral column grows slightly faster than does the spinal cord

cord seems to be drawn rostrally by its attachment to the brain

Front 408

the brainstem consists of:

Back 408

myeloencephalon (medulla oblongata)
pons (part of the metencephalon)
mesencephalon (midbrain)

Front 409

although developmentally the cerebellum is a part of the metencephalon, it is considered a "________________" structure and not a part of the brainstem

Back 409

suprasegmental

Front 410

the caudal part of the brainstem is the ______________________

Back 410

medulla oblongata

Front 411

the __________________ nucleus forms a continuous cell column from the cord-medulla junction to midpontine levels

Back 411

spinal trigeminal nucleus

Front 412

motor neurons in the brainstem originate from the ____________ plate

Back 412

basal

Front 413

the rostral-caudal segmentation of the developing rhombencephalon divides it into ________________

Back 413

rhombomeres

Front 414

rhombomeres are sites of _________________ gene expression

Back 414

homeobox (hox)

master switches that control formation of large blocks of tissue

Front 415

the cerebellum arises from the ________________, an alar plate structure that forms part of the wall of the fourth ventricle

Back 415

rhombic lip

Front 416

the rostral part of the rhombic lip forms the _______________, whereas the caudal part forms the _____________, _______________, and ______________ nuclei

Back 416

cerebellum

inferior olivary
cochlear
pontine

Front 417

the cerebral cortex is develloped using an ___________________ pattern of development, in which the neurons take up positions close to the ventricular surface and subsequent ones move progressively closer to the pial surface

Back 417

inside-out

Front 418

by the end of the _________________, the longitudinal cerebral, sylvian, and transverse cerebral fissures are recognizable

Back 418

first trimester

Front 419

a condition in which the cerebral cortex has a smooth surface, caused by a failure of gyri to form is known as _________________________

Back 419

lissencephaly

Front 420

a condition in which gyri are unusually large is called _________________

Back 420

pachygyria

Front 421

a condition in which gyri are unusually small is called _________________

Back 421

microgyria

Front 422

the term _______________ is used to describe the defect in which the migration of immature neurons from the ventricular surface is disrupted

Back 422

heterotopia

mature neurons take up residence in the intermediate zones

Front 423

_____________________ is a condition in which there are unilateral or bilateral clefts in the cerebral hemispheres

Back 423

schizencephaly

Front 424

three important parameters in brain organization are:

Back 424

1. density of neurons
2. pattern of axon and dendrite branching
3. pattern of synaptic contacts

(begin to develop at the sixth month of gestation - end of the peak period of neuronal migration)

Front 425

embryogenesis produces__________________ neurons than are present in the mature brain; they are almost all produced before week 24 and then begin to die selectively

Back 425

1.5 to 2 times more

Front 426

genetically programmed cell death is called ______________

Back 426

apoptosis

Front 427

nerve growth factor, brain-derived neurotrophic factor, and fibroblast growth factor are know to limit cell death by _______________________________

Back 427

interrupting the normal process of apoptosis

Front 428

_______________ guide a cell toward a particular target

Back 428

tropic factors

Front 429

_______________ maintain the metabolism of a cell or its processes

Back 429

trophic factors

Front 430

after neuroblasts complete their final cell division and migrate to their final location, they begin to extend a single axon with one or more distal elaborations known as ____________

Back 430

growth cones

Front 431

once an axonal growth cone arrives at its site of termination, it undergoes biochemical and morphologic changes to become a ___________________

Back 431

presynaptic terminal

Front 432

a synapse that forms will persist only if it exchanges the right cues with the target cell, so only a subset of the large number formed are retained; this concept is known as _______________

Back 432

synaptic stabilization

Front 433

synaptic stabilization requires:

Back 433

1. a signal generated by the presynaptic cell (e.g. neurotransmitter)

2. a means for the postsynaptic cell to respond

3. a retrograde signal from the post- to pre-synaptic cell to say contact should remain into maturity

Front 434

the developing brain is not as vulnerable to injury as is the mature brain; this concept is known as _________________

Back 434

plasticity

infants with significant cortical injury prenatally or early postnatally can show surprising functional recovery

Front 435

the period of time during which plastic changes can occur in the innervation (such as the input from the eyes) is called the __________________

Back 435

critical period

Front 436

the condition in which the visual cortex responds only to inputs from a "good" eye (ignores inputs from the other eye) is called _______________

Back 436

amblyopia

Front 437

synaptic development occurs _____________ with cellular proliferation and migration

Back 437

in parallel

Front 438

many children with mental retardation, including those with ___________________, have fewer and less complex axonal and dendritic amplifications and fewer dendritic spines than in normal children

Back 438

Down syndrome

Front 439

____________________ myelinate neuronal axons in the CNS

Back 439

oligodendrocytes

Front 440

myelination begins at about the ______________ of development

Back 440

sixth month

peaks between birth and first year of life, but continues into adulthood

Front 441

what is the hierarchy in the regional maturation of myelin formation?

Back 441

motor and sensory tracts first

association tracts later