Ch 9 Ans

Front 1

Dorsal Horn

Ventral Horn

Back 1

the spinal cord extends from the brain stem, enclosed in the vertebral canal

-Inside of canal: gray matter (outside = white matter)

Gray matter is arranged with a left & right dorsal horn, and a left & right ventral horn.

dorsal horn = sensory neurons

ventral horn = motor neurons

Front 2

Peripheral Nervous System

Back 2

Afferent (ascending) and Efferent (descending) nerves fibers relay info to and from CNS

Afferent: sensory receptors and nerves

Cell bodies for nerves are in the dorsal root ganglian

(Recall: sensory neurons are pseudo unipolar)

Efferent: divided into 2 branches

-Autonomic motor nervous system

-Somatic motor system

Afferent:(sends message to CNS)

Efferent: (sends away from CNS to muscles/effector)

Front 3

Somatic motor neurons

Back 3

always have cell bodies in the spinal cord and just one neuron traveling from spinal cord to effector (skeletal muscle tissue).

Front 4

The autonomic motor system

Back 4

has two sets of neurons in the PNS.

1. The first has cell bodies in the brain or spinal cord and synapses in an autonomic ganglion---(synapse between the pre and the post!)

2. The second has cell bodies in the ganglion and

synapses on the effector (smooth & cardiac muscle).

Front 5

Autonomic Nervous System

Back 5

A component of the peripheral nervous system

Control system functioning below the level of consciousness

-Involuntary functions

Influences heart rate, digestion, respiratory rate, perspiration, pupil dilation, micturition rate, sexual arousal

Higher level interaction with CNS

-Medulla oblongata (respirator centers and more)

-Hypothalamus acts as an integrating center as well

Front 6

Autonomic Motor Nerves

Back 6

Innervate organs not under voluntary control

Effectors include:

-Cardiac muscle

-Smooth muscle of visceral organs and blood vessels

-Glands

Front 7

how is autonomic motor neurons different from somatic motor neurons

Back 7

Somatic: go from CNS directly to effector (cell bodies in spinal cord)

Autonomic: 2 neurons

-Preganglionic: Cell body in gray matter of spinal cord

Travels from CNS (spinal cord) to 2nd neuron

Typically myelinated

Postganglionic: axon from 1stpreganglionic neuron to effector organTypically unmyelinated

Synapse: autonomic ganglion

Front 8

Visceral Effector Organs

Back 8

Organs controlled by the autonomic NS

Somewhat independent of innervation and will not atrophy if a nerve is cut (unlike skeletal muscle)

-Cardiac muscle and some smooth muscle contract rhythmically without nerve stimulation. Autonomic innervation can speed up or slow down intrinsic contractions.

(ex: heart can still operate without ANS: ANS can modify its activity tho)

Unlike somatic motor neurons (which are always stimulatory), autonomic motor neurons can stimulate or inhibit.

Front 9

Autonomic Ganglia

Back 9

Located in the head, neck, and abdomen as well as in chains along either side of the spinal cord

Location of autonomic ganglia is a distinguishing feature between the Sympathetic & parasympathetic

Front 10

2 systems of the ANS

Back 10

Sympathetic:

-Preganglionic neurons originate in thoracic and lumbar levels of spinal cord

-Send axons to sympathetic gangliaParallel spinal cord

Parasympathetic:

-Preganglionic neurons originate in brain and sacral region of spinal cord

-Axons synapse to ganglia near or in effector organs

Front 11

Sympathetic Preganglionic Neurons

Back 11

Myelinatedaxons exit the spinal cord at ventral roots and diverge into white rami communicantes and then into autonomic ganglia at multiple levels.

White rami = entry point

gray = exit point

(for the chain ganglion)

(allows convergence & divergence )

Front 12

Sympathetic Postganglionic Neurons

Back 12

Unmyelinated axons of the postganglionic neurons form the gray rami communicantes, which return to the spinal nerve and travel with other spinal neurons to their effectors.

Front 13

sympathetic divison

Back 13

Pregranglionic neurons come from the theoretic and lumbar regions of the spinal cord

(AKA thoracolumbar division)

See fig 9.5

Front 14

sympathetic chain of ganglia

Back 14

The presynaptic neurons synapse in sympathetic ganglia that run parallel to the spinal cord called paravertebral ganglia. These are Interconnected to form sympathetic chain of ganglia.

Front 15

Divergence of neural pathways:

Back 15

Axons have collateral branches, so one presynaptic neuron can form synapses with several postsynaptic neurons.

-one single signal can influence many other neurons

Front 16

Convergence of neural pathways

Back 16

Several different presynaptic neurons (up to a thousand) can synapse on one postsynaptic neuron.

-tons of into projected on one single neuron

Front 17

Sympathetic chain of ganglia

Back 17

can end up at many diff levels

Front 18

convergence & divergence influence on Sympathetic Division

Back 18

Because preganglionic neurons can branch and synapse in ganglia at any level, there is:

Divergence: One preganglonic neuron synapses on postganglionic neurons at different levels.

Convergence: Several preganglionic neurons at different levels synapse on one postganglionic neuron.

Allows the sympathetic division to act as a single unit through MASS ACTIVATION.

-VERY IMPORTANT FOR FIGHT OT FLIGHT MECH.

mass activation prepares you for fight/flight

Front 19

Collateral Ganglia

Back 19

(synapse between pre & post neuron)

Some sympathetic neurons that exit the spinal cord below the diaphragm do not synapse in the sympathetic chain of ganglia.

Instead, they form splanchnic nerves, which synapse in collateral ganglia. Collateral ganglia include celiac, superior mesenteric, and inferior mesenteric ganglia.

Postganglionic neurons innervate organs of the digestive, urinary, and reproductive systems.

Front 20

The Adrenal Glands: a special case

Back 20

Composed of 2 very different parts:

1. Cortex (outer)

-Derived from mesodermal tissue

2. Medulla (inner)

-Derived from nueralcrest cells, ectoderm tissue

Front 21

Adrenal Glands: cortex + medulla functions

Back 21

Cortex (outer)

-Secretes steroid hormones

Medulla (inner)

-Innervated by Sympathetic preganglionic neuron

-Secretes epinephrine (adrenalin) into blood stream

-Behaves like a postganglionic sympathetic neuron: NT release of norepinephrine at synapse

Front 22

Adrenal gland

Back 22

-interface between blah and blah

Front 23

Summary of the Sympathetic Division

Back 23

-table 9.2

-huge amount of reaching out, and diversity

-mass action

Front 24

Parasympathetic Division

Back 24

Preganglionic neurons come from the brain or sacral region of the spinal cord. It is also called the craniosacral division.

They synapse on ganglia located near or in effector organs.

-called terminal ganglia

Front 25

Parasympathetic Division (diff from sympathetic?)

Back 25

Also called craniosacral division

Preganglionic neurons do not travel with somatic neurons in spinal nerves (as sympathetic postganglionic neurons do).

-Effectors in the skin and skeletal muscles (sweat glands, blood vessels) receive sympathetic but not parasympathetic innervation.

Front 26

PS: Cranial Nerves

Back 26

-form the top part of PNS (are coming right out of the brain)

Nerves emerge directly from the brain

12 pairs:

1 & 2 emerge from cerebrum (purely sensory)

3 –12 from brain stem

Cranial Nerve II: Optic nerve

-Not truly peripheral, extension of diencephalon

Front 27

Cranial Nerves and the Parasympathetic Division

Back 27

The occulomotor(III) (focus on light), facial (VII), glosso-pharyngeal (IX) (salivation), and vagus(X) nerves carry parasympathetic preganglionic neurons.

1. Occulomotor: Preganglionic fibers exit midbrain and synapse on the ciliaryganglion.

2. Postganglionic fibers innervate the ciliarymuscle of the eye. Critical for accommodation (focusing)

Front 28

Cranial Nerve X (10)

KNOW THIS NERVE:

Back 28

aka Vagus nerve (wondering nerve)(starts high, ends low then intervates):

1. Provides major parasympathetic innervation to the thoracic and abdominal cavities
2. Branches in to several plexiand nerves (vagrant nerve)
3. Synapses with postganglionic nerves within effect organs
4. -heart, lungs, esophagus, stomach, pancreas, liver, intestines

Front 29

Sacral Nerves

Back 29

Preganglionic nerves from the sacral region of the spinal cord provide innervation to the lower part of the large intestine, rectum, urinary and reproductive organs.

Terminal ganglia are located within these organs.

Front 30

Summary of Parasympathetic Division

Back 30

table 9 . 3

eye system extension of nerve system

Front 31

Comparison of the Sympathetic and Parasympathetic Divisions

Back 31

fig 9.5 (pg 249!!)

-come together to form automatic nervous system

Front 32

Sympathetic Functions

Back 32

The sympathetic division activates the body for “fight or flight” through the release of norepinephrine from postganglionic neurons and the secretion of epinephrine from the adrenal medulla.

-Prepares the body for intense physical activity in emergencies by increasing heart rate and blood glucose levels and by diverting blood to skeletal muscles

(Mass Action capability)

Front 33

Parasympathetic Functions

Back 33

The parasympathetic division is antagonistic to the sympathetic division.

Allows the body to “rest and digest” through the release of ACh from postganglionic neurons.

-Slows heart rate, dilates visceral blood vessels, increases digestive activities

Front 34

ANS Neurotransmitters

Back 34

Both Symp & Parasymp preganglionics release ACh: - called cholinergic synapses

Difference:

Most Symp post ganglia release Norepinephrin(noradenaline) -Called adrenergic synapses

1. A small number release ACh

Front 35

somatic vs autonomic

Back 35

type of neuron macular junction

-lack of specialization

Front 36

Varicosities: a different kind of synapse in the ANS

Back 36

Axons of postganglionic neurons have various swellings called varicosities that release neurotransmitter along the length of the axon.

(dumping out neurotransmitter in the smooth muscle)(as it moves through)

They form “synapses en passant” (in passing).

Front 37

Antagonistic Effects:

Back 37

Fight or Flight vs. Rest and Digest

Sympathetic and parasympathetic neurons innervate the same tissue

Elicit opposite responses

Example: smooth muscle response

1. Sympathetic: norepinephrin/adrenergic receptors

2. Parasymp: acetylcholine/cholinergic receptors

Front 38

Complementary Effects

Back 38

Occur when both divisions produce similar effects on the same target

Example:

-Salivary gland secretion: Parasympathetic division stimulates secretion of watery saliva; sympathetic constricts blood vessels so the secretion is thicker.

(Both made you salivate, but the end is different)

Front 39

Cooperative Effects

Back 39

-Occur when both divisions produce different effects that work together to promote a single action:

Example:

1. Erection and ejaculation: Parasympathetic division causes vasodilation and erection; sympathetic causes ejaculation

2. Urination: Parasympathetic division aids in urinary bladder contraction; sympathetic helps with bladder muscle tone to control urination.

Front 40

ANS variability: to stimulate or to inhibit?

Back 40

Response to AP in visceral organ depends on whether its from a sympathetic or parasympathetic neuron

-Sympathetic = norephinephrine(NE)

-Parasympathetic = acetylcholine (ACh)

In many instances the same NT can elicit opposite responses

Due to different types of receptors responding to the same NTs (epinephrine/norepinephrine)

Front 41

Organs with Dual Innervation

Back 41

Most visceral organs are innervated by both sympathetic and parasympathetic neurons.

Most of the time these systems are antagonists:

-Heart rate (PS down, S up)

-Digestive functions (PS up, S decrease)

-Pupil diameter (PS down, S up)

Front 42

Organs Without Dual Innervation

Back 42

The following organs are innervated by the sympathetic division only:

-Adrenal medulla

-Arrector pili muscles in skin

-Sweat glands in skin

-Most blood vessels

Regulated by increase and decrease in sympathetic nerve activity

Important for body temperature regulation

Front 43

Control of ANS by the Brain

Back 43

Many visceral functions are regulated by autonomic reflexes.

1. Sensory input is sent to brain centers (usually by the vagus nerve), which integrate the information and modify the activity of preganglionic neurons.

2. Medulla oblongata controls many cardiovascular, pulmonary, urinary, reproductive, and digestive functions.

Front 44

Regulation of the Medulla

Back 44

Higher brain regions regulate the medulla.

1. Hypothalamus: major regulatory center of the ANS

2. Limbic system: responsible for autonomic responses during emotional states (blushing, pallor, fainting, sweating, racing heart rate)