The Autonomic Nervous System

Question 1

ANS vs Somatic NS

Answer 1

somatic - neurons synapse directly onto effector

ANS - the CNS controls the effectors via two neuron chain (preganglionic and post panglionic)

Question 2

Symp. nervous system alone controls most…

Answer 2

vascular smooth muscle and all smooth muscle in the limbs and body walls (BVs, erector pili muscle, glands)

Question 3

There is no parasymp. innervation of

Answer 3

the body wall

Question 4

Preganglionic neuronal cell bodies in the CNS

Answer 4

• symp NS has cell bodies in the thoracolumbar division (T1 - L2) in lateral gray horns
• parasymp has cell bodies in craniosacral division, brainstem cranial nerve nuclei (TRAVEL THROUGH CN III, VII, IX, (viscera of face) AND X (viscera of gut)) and spinal cord S2-S4 levels

Question 5

Postganglionic neuronal cell bodies in the PNS

Answer 5

• symp ganglia located near spinal cord in the paired sympathetic chain ganglia which target smooth muscle and viscera of head and thorax OR unpaired preaortic ganglia which target viscera of abdomen and pelvis
• parasymp ganglia located in or near effector organs

Question 6

Both preganglionic neurons use ____ and act on ____

Answer 6

• ACh

- nicotinic ACh receptors and ligand gated ion channels (always stimulatory)

Question 7

Postganglionic neurons of parasymp NS use ____ and act on ____

Answer 7

• ACh

- muscarinic ACh receptors (stim and inhib effects)

Question 8

Postganglionic neurons of symp NS use ____ and act on ____

however two exceptions are

Answer 8

• norepinephrine
• NE receptors
• adrenal medulla (releases more epi than NE)
• sweat glands release ACh

Question 9

Interomediolateral cell column (IML)

Answer 9

present at certain levels of spinal cord (T1-L2 and S2-S4) contains autonomic preganglionic motor neurons, conducts output via the ventral roots and ensuing nerves

Question 10

Somatic vs Sympathetic innervation of the body wall and limbs

Answer 10

somatic innervation

• motor neurons have cell bodies in ventral grey horn of spinal cord, axons leave through ventral root and then join sensory axons to become a spinal nerve and exit via the rami
• sensory neurons monitor skin, joints whatever and then have cell bodies in DRG, axons convey info to dorsal grey horn

sympathetic innervation
- preganglionic neurons in grey matter centre, post gang cell bodies in symp chain

Question 11

Preganglionic symp fibres can ______ before synapsing

Answer 11

ascend or descend

Question 12

autonomic plexus

Answer 12

when symp postganglionic nerve hitches a ride with arties to reach target (in the face)

Question 13

Preaortic unpaired ganglia innervate…

Answer 13

abdominopelvic viscera

- celiac - , superior mesenteric - , inferior mesenteric ganglia

Question 14

Adrenal medulla

Answer 14

modified symp ganglion, innervated by preganglionic symp neurons of lateral grey horns
- post gang neurons of adrenal medulla release Epi and NE

Question 15

Visceral Pain

Answer 15

viscera are insensitive to cutting, burning freezing.

visceral pain is caused by ischemia, distension, inflammation, blood and usually travels with sympathetic efferents

Question 16

Referred pain of heart attack

Answer 16

pain afferents from heart travel with symp efferents back to spinal cord levels T1-T5 so in the spinal cord, overlap with afferents from the T1-T5 dermatomes makes u think heart pain is coming from arm and chest

Question 17

A given peripheral nerve may have fibres from both

Answer 17

the somatic nervous system and the ANS (smooth muscle and skeletal muscle are in similar spots so it mixes)

Question 18

autonomic preganglionics are in the

Answer 18

interomedial lateral cell column and conduct via the ventral roots (go out and synapse on post ganglionic cells in the symp chain)