Chapter 13: The Spinal Cord, Nerves And Reflexes

Front 1

SPINAL CORDFUNCTIONS

Back 1

conduction

locomotion

central pattern generators

reflexes

Front 2

conduction

Back 2

conduct information up and down the cord

Front 3

locomotion

Back 3

repetitive, coordinated contractions of muscles of thelimbs initiate walking

Front 4

central pattern generators

Back 4

groups of neurons causing the alternating movements of the leg muscles

Front 5

reflexes

Back 5

involuntary, stereotyped responses involving the brain,spinal cord and peripheral nerves

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Terminology PNS

Back 6

1. ganglia

2. nerves

3. spinal

4. cranial

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ganglia

Back 7

collection of neuron cell bodies

Front 8

Nerves

Back 8

bundles of axons

Front 9

spinal nerves

Back 9

connected to the spinal cord

Front 10

cranial nerves

Back 10

connected to the brain

Front 11

TerminologyCNS

Back 11

8. motor (descending) pathway

7. sensory (ascending) pathway

6. columns

5. tracts

4. higher centers

3. neural cortex

2. nucleus

1. center

Front 12

spinal cord

Back 12

cylinder of nervous tissue passing through the vertebralcolumn, beginning at the foramen magnum and ending at L1

-includes 31 pairs of spinal nerves that pass throughintervertebral foramina

- has valley-likeindentations running along the midline called the posterior median sulcus andanterior median fissure

-divided into cervical,thoracic, lumbar, and sacral regions

- quantity of gray matter increases in areas involved withsensory and motor control of limbs

Front 13

posterior median sulcus

Back 13

midline

Front 14

anterior medianfissure

Back 14

midline

Front 15

Cervical enlargement

Back 15

supplies nerves of the upper limbs

Front 16

Lumbar enlargement

Back 16

supplies nerves of the pelvic region and lower limbs

Front 17

conus medullaris

Back 17

tapered point at the terminal end of the spinalcord

Front 18

cauda equina

Back 18

“horse tail” bundle of nerve roots from L2 to S5

Front 19

3 layers of spinal meninges

(fibrous connective tissues that separate the soft tissue ofthe CNS from the bones)

Back 19

Dura Mater

Arachnoid Mater

Pia Mater

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Dura mater

Back 20

tough collagenous membrane forms a loose fittingsleeve called a “dural sheath” around the spinal cord

Front 21

epidural space

Back 21

superficial to dura mater, filled with adiposeand blood vessels

Front 22

epidural block

Back 22

affects the area immediately around the site ofinjection

Front 23

arachnoid mater

Back 23

layer of simple squamous epitheliumthat adheres to the dura mater, creates a mesh of collagenous and elasticfibers spanning a gap

Front 24

Subarachnoid space

Back 24

a gap spanningof collagenous and elastic fibers filled with cerebral spinal fluid (CSF)

Front 25

pia mater

Back 25

delicate, translucent membranedirectly adhering to the spinal cord

Front 26

terminal filum

Back 26

fibrous extension of the pia mater that anchorsthe spinal cord to the coccyx

Front 27

denticulate ligaments

Back 27

extend from pia mater through arachnoid materand attach to dura mater, prevent side to side movement

Front 28

Meningitis

Back 28

inflammation of the meninges, possibly due to infection by abacteria or virus

Front 29

Lumbar puncture (spinal tap)

Back 29

withdrawal of CSF from the lumber region, to avoid injury tothe spinal cord, cloudiness may indicate bacterial infection

Front 30

graymatter

Back 30

contains the somas, dendrites and proximal partsof the axons of neurons, it is the site of synaptic contact between neurons andprocesses information

Front 31

white matter

Back 31

contains bundles of axons, called tracts that carry signals from one part of CNS to another

Front 32

Gray Matter

Back 32

shaped like a butterfly in the spinal cord

composed of:

Dorsal (posterior)gray horns

Ventral (anterior)gray horns

lateral gray horns(from T2-L1)

gray commissure

Front 33

Dorsal (posterior) gray horns

Back 33

receive somatic and visceral sensoryinformation from dorsal root

Front 34

Ventral (anterior) gray horns

Back 34

contain somas of somatic motorneurons with axons exiting the ventralroot

Front 35

lateral gray horns(from T2-L1)

Back 35

contain visceral motorneurons of the sympathetic nervous system

Front 36

gray commissure

Back 36

how the horns are connected

Front 37

White Matter

Back 37

- axon bundles arranged in 3 pairs called columns (funiculi)

1) dorsal (posterior) white column

2) ventral (anterior) white column

3) lateral white column

-column divided into tracts (fasciculi)

*ascending tracts

* descending tracts

Front 38

ascending tracts

Back 38

carry sensoryinformation toward the brain

Front 39

descending tracts

Back 39

carry motorinformation from the brain

Front 40

spinal nerves

Back 40

includes 31 pairs of nerves along the vertebral column, 8cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal

Front 41

nerve

Back 41

a cord composed of many nerve fibers (axons) bound togetherby connective tissue, contains from a few to millions of nerve fibers

Front 42

epineurium

Back 42

dense irregular connective tissue surrounding abundle of fascicles, protects the nerve from stretching and injury

Front 43

fascicle

Back 43

a bundle of nerve fibers

Front 44

perineurium

Back 44

connective tissue surrounding a fascicle

Front 45

Endoneurium

Back 45

loose connective tissue surrounding an individual nervefiber

Front 46

dermatome

Back 46

a region of skin monitored by a spinal nerve,each has a 50% overlap with adjacent regions

Front 47

peripheral neuropathies

Back 47

losses of sensory or motor function from nervedamage

Front 48

Shingles

Back 48

caused by the chickenpox virus (Varicella-Zoster Virus),after you get chickenpox, the virus hides in your dorsal root ganglia and mayreemerge later in life as shingles- symptoms include rash and blisters along a dermatomewith intense itching and sometimes post-herpeticneuralgia or nerve pain

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post-herpetic neuralgia

Back 49

nerve pain

Front 50

dorsalroot

(sensory)

Back 50

divides into 6-8 nerve rootletsthat enter the spinal cord

-includes a swellingcalled the dorsal root ganglionwhich contains somas

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dorsal root ganglion

Back 51

a swelling which contains somas

Front 52

ventral root

(motor)

Back 52

6-8 rootlets formconverge from the spinal cord

Front 53

Distal Branches

Back 53

once the nerve exits the vertebral columnthrough the intervertebral foramen, the nerve divides into 3 branches:

1)dorsal ramus

2) ventral ramus

(sensory and motor -mixed)

3)rami communicantes

(motor- sympathetic)

Front 54

cervical Plexus

Back 54

innervates skin of the neck andswallowing muscles , most importantly the phrenic nerves

Front 55

phrenic nerves

Back 55

innervate the diaphragm and aid in breathing, ifirritated causes hiccups

Front 56

brachial Plexus

Back 56

innervates the upper limb and some muscles of the neck and lower shoulder

Front 57

axillary nerve

Back 57

deltoid and skin of shoulder

Front 58

musculocutaneous nerve

Back 58

biceps brachii and skin of lateral forearm

Front 59

median nerve

Back 59

flexors of forearm and skin ofanterolateral hand; if injured like when wrist slashing, makes it hard to use the pincer grasps

Front 60

Ulnar nerve

Back 60

flexor digitorum profundus andmedial surface of hand; injury would hinder your ability to make a fist,stimulates “funny bone”

Front 61

radialnerve

Back 61

extensor muscles of arm and forearmand skin of posterolateral limb; may be injured by improper crutch use, causeswrist drop a chronic flexing of the fingers, hand and wrist

Front 62

Lumbar Plexus

Back 62

lower back

Front 63

femoral nerve

Back 63

quadriceps and skin of anteromedial thigh

Front 64

Sacral Plexus

Back 64

around sacrum

Front 65

sciatic nerve

Back 65

composed of the tibial and common fibular nerves traveling together; controls muscles and skinof the back thigh and whole leg; most vulnerable nerve in the body

**trauma causes sciatica,a sharp pain running from the gluteal area down the leg

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Coccygeal Plexus

Back 66

lower sacrum and coccyx

Front 67

neural pool

Back 67

1,000’s or millions of interneurons assembled together inone particular function, like controlling the beating of your heart orregulating your sense of hunger- information arrives at a neural pool through one or moreinput neurons, forming multiple synapses with the same postsynaptic cell

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discharge zone

Back 68

the area of a neural pool in which the input neuron can cause an action potential

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facilitated zone

Back 69

- the area outside of the discharge zone in aneural pool in which the input neuron can not cause an action potential, UNLESSaided by other input neurons

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neural circuit

Back 70

the pathways of the neurons that make up aneural pool

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Divergence circuit

Back 71

one presynaptic nerve fiberbranches and synapses with several postsynaptic cells; broad distribution of asignal as when sensory neurons bring information to different parts of thebrain

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convergence circuit

Back 72

many presynaptic nerve fibers combine to formone postsynaptic neuron; allows for conscious and unconscious control of breathing

Front 73

serial processing

Back 73

one neuron to another neuron, as from one partof brain to another

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parallel processing

Back 74

a single input neuron splits to stimulateseveral chains of neurons, each with a different number of synapses; allowsmany responses as same time as when you step on a tack leads to withdraw of onefoot, extension of the other foot, the feeling of pain and the screaming thatfollows

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reverberating circuit

Back 75

several single neurons stimulateeach other in sequence,A à B àC àD, except neuron C actually restimulates neuron A causing a repetitious signal that echoes or“reverberates” like a positive feedback loop -this occurs during a single inhalation of the lungs

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Reflex

Back 76

quick, involuntary, stereotyped reactions of glands ormuscles to stimulationProperties of reflexes

1. requirestimulation

2. quick, have few interneurons or synaptic delays

3. involuntary

4. stereotyped

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somatic reflexes

Back 77

involve the somatic nervous system

Front 78

reflex arc

Back 78

neural pathway of a reflex signal

1. somatic receptorsin skin, muscle, or tendon

2. afferent nervefibers carry information to the dorsal horn of spinal cord or brainstem

3. integrating center synaptic contact in the gray matter

4. efferent nerve fibers carry motor impulses to

5. somatic effectors, the skeletal muscles

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monosynaptic reflex arc

Back 79

the afferent fibers synapse directly with thealpha motor neurons that return to the muscle, allowing only one synapse, thusmaking the reflex extremely quick

Front 80

stretch (myotatic) reflex

Back 80

a response to a stretched muscle in which the musclecontracts - important in stabilizing joints by balancing the tensionof extensors and flexors

Front 81

patellar reflex

Back 81

doctor taps patellar ligament with reflexhammer, stretches quad and results in extension of the leg

Front 82

muscle spindles

Back 82

stretch receptors embedded in the skeletal muscles, involvedin somatic reflexes, make up part of the body’s proprioceptors

- muscle spindles inform the brain of muscle length and bodymovements

- very abundant in muscles that require fine control andconcentrated near the tendons

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extrafusal fibers

Back 83

muscle fibers outside the spindle, the “worker”muscle fibers

Front 84

intrafusal fibers

Back 84

modified muscle fibers within aspindle that can only contract at its ends

Front 85

alpha motor neurons

Back 85

innervate the working part of the muscle,extrafusal fibers

Front 86

gamma motor neurons

Back 86

innervate and stimulate the contraction of theends of intrafusal fibers adjusting the sensitivity of the muscle spindle

Front 87

polysynaptic reflex arc

Back 87

a pathway in which signals travel over many synapses ontheir way back to a muscle, a parallel after-discharge circuit, to create asustained contraction

1. tendon reflex­

2. Withdrawal reflex

Front 88

1. tendonreflex­

Back 88

reflex of contracting a muscle when the tendonis stretched

Front 89

golgi tendon reflex

Back 89

a response to excessive tension ona tendon, prevents alpha neurons from contracting so strongly

Front 90

golgi tendon organs

Back 90

proprioceptors located in a tendon near itsjunction with a muscle

Front 91

Withdrawal reflex

Back 91

pulling away from a painful stimulus

Front 92

flexor reflex

Back 92

quick contraction of flexor musclesto withdrawal a limb from possible injury

Front 93

Reciprocal inhibition

Back 93

as a muscle contracts in a reflex, theantagonist muscle is inhibited from movement to prevent the muscles fromworking against each other

Front 94

crossedextensor reflex

Back 94

contraction of extensor muscles in the limb opposite the onebeing withdrawn to keep your balance

Front 95

ALS (amyotrophic lateral sclerosis)

Back 95

“Lou Gehrig’s Disease”, progressive destruction of anteriorhorn and pyramidal tracts, resulting in the loss of speech, swallowing andbreathing

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Poliomyelitis

Back 96

destruction of anterior horn motor neurons bypolio virus

Front 97

Neuralgia

Back 97

nerve pain, caused by pressure from herniateddiscs

Front 98

Paresthesia

Back 98

sensations of prickling, burning, numbness, or tingling dueto nerve trauma or disorders

Front 99

Erb’s Palsy

Back 99

obstetric condition characterized by paralysisor weakness of a newborn’s upper arm muscles caused by a stretch injury to thebrachial plexus

Front 100

Paraplegia

Back 100

paralysis of lower limbs

Front 101

Quadriplegia

Back 101

– paralysis of sensory and motor control ofupper and lower limbs

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done

Back 102

done