Visceral Autonomic Nervous System

Question 1

What tissues are innervated by the ANS?

Answer 1

smooth muscle

cardiac muscle

glands

Question 2

In general, where are the 2 neurons in the ANS located?

Answer 2

the first is in the brain stem or spinal cord (in the CNS)

the second is in a peripheral ganglion (motor)

Question 3

What are the two branches of the ANS?

Answer 3

sympathetic and parasympathetic

Question 4

Where are the sympathetic preganglionic neuron cell bodies located?

Answer 4

in the lateral horns of the spinal cord segments T1-L2

Question 5

Where are parasympathetic preganglionic neuron cell bodies located?

Answer 5

in the cranial nerve nuclei of the CN 3, 7, 9, and 10 and the spinal cord segments S2-S4

Question 6

Where do the presynaptic neurons synapse in the sympathetic systems?

Answer 6

3 choices:

they synapse onto the postganglionic neuron in the paravertebral ganglia or sympathetic chain along the sides fo the spinal cord

they pass through the paravertebral ganglia into the splanchnic nerves and synapse onto the postganglion neuron in the prevertebral ganglia

they pass through the ganglia iwthout synapsing and synapse on the secretory cells of the adrenal gland

Question 7

How doe the sympathetic preganglionic nerve fibers get to the paravertebral ganglia?

Answer 7

THey leave the spinal cord through the ventral roots and join the spinal nerve

they enter the ventral rami

soon after entering the rami, they enter a white ramus communicans which is attached to the paravertebral ganglia

Question 8

Once the preganglionic neuron is in the paravertebral ganglia, what are its 4 options?

Answer 8

1. it can synapse right at that same level
2. It can ascend to terminate at a higher paravertebral level
3. It can descend to a lower paravertebral level
4. I can traverse the sympathetic trunk without terminating and form splanchnic or visceral nerves

Question 9

Where must sympathetic innervation of the head come from?

Answer 9

remember that all sympathetic nerves originate in the thoracolumbar spinal cord - NOT the cervical. So the head comes from around T1-T2.

Question 10

Why are white rami communicans white?

Answer 10

the axons inside are myelinated

Question 11

Besizdes the preganglionic sympathetic axons, what could be present in the white communicating rami?

Answer 11

visceral sensory fibers

Question 12

How many pairs of white rami are there in the spinal cord?

Answer 12

14 pairs - 28 total

Question 13

Paravertebral ganglia are usually arranged segmentally with one per spinal nerve EXCEPT in what region?

Answer 13

cervical - there are only 3

these have communications with the 8 cervical spinal nerve

Question 14

How do the paravertebral ganglia communicate the postganglionic sympathetic fibers back to the 31 pairs of spinal nerves?

Answer 14

through gray rami communicans

thus, there are 31 pairs of gray rami

Question 15

How do sympathetic postganglion fibers reach the head?

Answer 15

they go thorugh the cephalic arterial branches

(also called the periarterial sympathetic plexus)

they leave the superior cervical ganglia and jump onto the carotic arteris (or any other vessel) and follow them to their destinations

Question 16

Why is the superior cervical ganglion the largest of the cervical ganglia?

Answer 16

because thats where the postganglionic fibers for the head come out

Question 17

How to postganglionic axons reach the heart, lungs, and esophagus?

Answer 17

They leave the paravertebral ganglia via cardiopulmonary nerves that supply the cardiac, pulmnary and aortic plexuses

Question 18

Where are the cell bodies of the cardiopulmonary nerves?

Answer 18

they are in the middle and inferior cervical paravertebral ganglia or in the upper 5 thoracic paravertebral ganglia

Question 19

What are the 3 main prevertebral ganglia?

Answer 19

celiac ganglion

superior mesenteric ganglion

inferior mesenteric ganglion

Question 20

How do preganglionic fibers get to the prevertebral ganglia from the sympathetic chain?

Answer 20

they leave the sympathetic chain through splanchnic nerves

Question 21

What are the equivalents of postganglioni neurons in the suprarenal medulla? WHat do they do?

Answer 21

the secretory cells fo the suprarenal medulla

they release primarily epinephrine into the vascular system

Question 22

What neurotransmitter is released from preganglionic sympathetic neurons? What receptor do they act on?

Answer 22

they release acetylcholine which acts on nicotninic receptors located in the membrane of postganglionic neurons

Question 23

What NT do the postganglionic neurons release? Onto what receptors?

Answer 23

norepinephrine on alpha or berta receptors on the target organ

Question 24

What alpha/beta recetors are excitatory? Which are inhibitory?

Answer 24

alpha and beta 1 are excitatory

alpha 2 and beta 2 are inhibitory

Question 25

Where are preganglionic cell bodies located in the parasympathetic system?

Answer 25

brain stem (for CN 3, 7, 9, 10) and sacral spinal cord (S2-4)

Question 26

Where are the parasympathetic postganglionic cell bodies?

Answer 26

the ones in the head regions are in distinct cranial ganglia

those from the vagus nerve and sacral regions are in or near the organ of innervation in terminal ganglia

Question 27

WHat NT is released by preganglionic parasympathetic neurons? on what receptor?

WHat NT is released by postganglionic parasympathetic neurons? On what receptor?

Answer 27

Preganglionic: ACh on nicotinic receptors

Postganglionic: ACh on muscarinic receptors

Question 28

Which ANS system has short presynaptic neurons and long postsynatic neurons?

Which has the reverse?

Answer 28

sympathetic

the reverse is parasympathetic

Question 29

WHy type of fibers are in the myenteric nerve plexus?

Answer 29

postganglionic parasympathetic neurons

this is an example of a terminal ganglion in the organ of innervtion