Autonomic Nervous System

Question 1

what is the autonomic nervous system

Answer 1

the visceral motor division of the peripheral nervous system
*provides motor innervation to smooth muscle, cardiac muscle, and glands

Question 2

2 divisions of ANS

Answer 2

1) sympathetic
2) parasympathetic

Question 3

how can the CNS influence the ANS

Answer 3

1) sensory feedback from viscera (stretch, pressure, chemical changes, temperature, irritation)
2) higher cognitive influence (learned behaviors, memory, emotion, mood, fear, stress)
3) brainstem and spinal visceromotor centers
4) HYPOTHALAMUS***

Question 4

two-neuron circuit: SYMPATHETIC nervous system

Answer 4

1) short pre-ganglionic neuron synapses in a ganglia in the sympathetic chain, with Ach onto a nicotinic receptor
2) long post-ganglionic neuron travels from sympathetic chain to effector organ, delivering norepinephrine onto an adrenergic receptor (alpha or beta)

Question 5

two-neuron circuit: SYMPATHETIC to sweat glands

Answer 5

1) short pre-ganglionic neuron synapses in a ganglia in the sympathetic chain, with Ach onto a nicotinic receptor
2) long post-ganglionic neuron travels to sweat glands and delivers Ach onto a muscarinic receptor

Question 6

one-neuron circuit: SYMPATHETIC to adrenal medulla

Answer 6

*pre-ganglionic neuron travels to the adrenal medulla and delivers Ach onto a nicotinic receptor, stimulating release of epi and norepi from the gland

Question 7

two-neuron circuit: PARASYMPATHETIC nervous system

Answer 7

1) long pre-ganglionic neuron travels to its respective ganglion and delivers Ach onto a nicotinic receptor
2) short post-ganglionic neuron (often in the wall of the effector neuron) releases Ach onto a muscarinic receptor

Question 8

what is the role of the ANS

Answer 8

maintains homeostasis of the body using antagonistic systems (parasympathetic and sympathetic)

Question 9

role of the sympathetic nervous system

Answer 9

*fight or flight
*widespread / global
*works in concert with release of hormones from the adrenal gland

Question 10

general examples of sympathetic responses

Answer 10

*pupil dilation (mydriatic pupil)
*increased cardiac output
*dilated airway
*regulates local blood flow (increased to skeletal muscle, decreased to GI tract)
*decreases release of digestive enzymes
*decreased blood flow to skin
*increased sweating
*stimulation of erector pili in skin
*control of micturition and defecation
*cooperates in human sexual response

Question 11

role of the parasympathetic nervous system

Answer 11

*rest and digest / breed, read, and feed
*FOCAL response of separate targets that support behaviors

Question 12

general examples of parasympathetic responses

Answer 12

*pupillary constriction (miotic pupil)
*decreased cardiac output (rate and pressure)
*decreased blood flow to skeletal muscles
*constriction of airway
*increased gut motility for digestion
*glandular secretion (NOT sweat glands)
*micturition and defecation
*cooperates in human sexual response

Question 13

location of cell bodies of pre-ganglionic sympathetic neurons

Answer 13

lateral horn (intermediolateral cell column in spinal gray matter) of T1-L2

Question 14

location of cell bodies post-ganglionic sympathetic neurons

Answer 14

1) paravertebral ganglia (sympathetic trunk)
2) superior, middle, and cervical ganglia
3) prevertebral ganglia

Question 15

paravertebral ganglia

Answer 15

*ganglia regionally named and associated with each spinal nerve
*location of the majority of the cell bodies of post-ganglionic sympathetic neurons

Question 16

prevertebral ganglia

Answer 16

*ganglia associated with visceral branches of the abdominal aorta
*celiac, superior mesenteric, and inferior mesenteric ganglia

Question 17

white rami communicantes

Answer 17

*from spinal nerve for preganglionic axons to enter sympathetic trunk
*free to synapse or ascend or descend several segments before synapsing or leaving on splanchnic nerves without synapsing

Question 18

gray rami communicantes

Answer 18

“on ramp” for post-ganglionic axons rejoining spinal nerve to innervate peripheral targets

Question 19

splanchnic nerves

Answer 19

branches of sympathetic trunk innervating viscera in body cavities
(cardiac splanchnic nerves are post-ganglionic fibers going to the heart)
(abdominal splanchnic nerves are pre-ganglionic axons going to abdominal viscera)

Question 20

cervical cardiac nerves

Answer 20

*preganglionic fibers arise from T1-T4 spinal segments and synapse in the cervical and upper thoracic chain ganglia
*postganglionic sympathetics descend from the cervical ganglia to the cardiac plexus and its subsidiaries
*descend to thorax and mingle with other axons in cardiac plexus
*target = heart

Question 21

carotid plexus of sympathetic fibers to head

Answer 21

*postganglionic fibers are from neurons in superior cervical ganglion
*targets = sphincter of pupil, smooth muscle in upper lip, and sweat glands

Question 22

location of cell bodies of preganglionic parasympathetic neurons

Answer 22

1) brainstem (CNs III, VII, IX, and X)
2) spinal cord segments S2-S4 (pelvic splanchnic nerves)

Question 23

parasympathetics of CN III (oculomotor nerve)

Answer 23

*preganglionic PS neuron cell bodies = midbrain
*postganglionic PS neuron cell bodies = ciliary ganglion
*postganglionics follow V1
*target = pupillary sphincter muscle and ciliary muscle of the lens
*function = pupillary constriction & accommodation of lens for ‘near sight’

Question 24

parasympathetics of CN VII (facial nerve)

Answer 24

1) tearing/lacrimation
-target = lacrimal gland
-preganglionic cell bodies = caudal pons
-postganglionic cell bodies = pterygopalatine ganglion
-follows V2 (short ciliary)

2) salivation
-target = submandibular and sublingual glands
-preganglionic cell bodies = caudal pons
-postganglionic cell bodies = submandibular ganglion
-follows V3

Question 25

preganglionics of CN IX (glossopharyngeal nerve)

Answer 25

*target = parotid glands
*preganglionic cell bodies = rostral medulla
*postganglionic cell bodies = otic ganglion
*function = salivation
*follows V3

Question 26

parasympathetics of CN X (vagus nerve)

Answer 26

*targets: cardiac muscle, smooth muscle of respiratory tract, smooth muscle and glands of GI tract from esophagus to transverse colon
*preganglionic cell bodies = medulla (dorsal vagal nucleus)
*postganglionic cell bodies = remote collateral ganglion IN OR NEAR WALL OF ORGAN

Question 27

sacral parasympathetic outflow

Answer 27

*preganglionic neurons: S2-S4 intermediate gray matter
*postganglionic neurons: intramural ganglia
*responsible for parasympathetics starting at the splenic flexure (descending colon, sigmoid colon, rectum, lower urinary tract, including bladder & pelvic part of ureter, and reproductive organs)