Lecture 6 - Visceral Motor Control and the Autonomic Nervous System

Question 1

What are the two branches of the PNS and what are their subdivisions each?

Answer 1

-somatic (voluntary control) and autonomic (involuntary control)
-somatic is broken into sensory afferent neurons and motor efferent neuron
-autonomic is broken into sympathetic and parasympathetic

Question 2

What is the sympathetic branch?

Answer 2

fight or flight and it active during periods of high stress and also typically in periods in which large amounts of cortisol and norepinephrine are being made and released

Question 3

What is the parasympathetic branch?

Answer 3

rest and digest and active during periods of low stress

Question 4

What are the two types of neurons in the sympathetic branch?

Answer 4

-preganglionic neurons - in lateral horn of the spinal cord, myelinated, and release acteylcholine
-postganglionic neurons - found in the sympathetic chain thoracic to lumbar spinal cord or splanchnic ganglia which is found in the lateral proximal sacral spinal cord; unmyelinated and release norepinephrine

Question 5

What are the two types of neurons in the parasympathetic branch?

Answer 5

-preganglionic neurons - found in the lower brainstem or the upper cervical spinal cord and the sacral spinal cord; release acetylcholine via nicotinic receptors

-postganglionic neurons - found adjacent to target organs in the periphery and they release ACh signal via muscarinic receptors

Question 6

What cranial nerves provide autonomic control for the eyes and face?

Answer 6

CN III-X

Question 7

What does the CN X or the vagus nerve provide autonomic control for?

Answer 7

all the visceral organs except the bladder, distal bowels, and genitalia

Question 8

What is the baroreflex?

Answer 8

modulates blood pressure

Question 9

What do baroreceptors do?

Answer 9

they are in the aortic arch of the heart and send signal about blood pressure at any moment in time

Question 10

What sends information about blood gas levels?

Answer 10

chemoreceptors

Question 11

What do the baroreceptors do when blood pressure is high in the aortic arch?

Answer 11

-they send impulses to the brainstem which is specifically the Nucleus of the Solitary Tract (NTS)

Question 12

Whats does the NTS stimnulate?

Answer 12

-preganglionic neurons from parasympathetic branch in the Nucleus Ambiguus in the brainstem

Question 13

What does the nucleus ambiguus do?

Answer 13

project via the CN X or the vagus nerve to the postganglionic neurons in the cardiax plexus which is where acetylcholine is released

Question 14

Where is the inhibitory signal sent during the baroreflex?

Answer 14

the preganglionic neurons in the sympathetic branch in the thoracic spinal cord which causes a reduction in the amount of norepinephrine released

Question 15

What are the parasympathetic synapses for the baroreflex?

Answer 15

baroreceptors —-> NTS—–>nucleus ambiggus—–>vagus nerve CN X —-> cardiac plexus ACh release

Question 16

What are the sympathetic reflexes for the baroreflex?

Answer 16

baroreceptors—–> sympathetic chain ganglion in the thoracic spinal cord —–> reduced norepinephrine release

Question 17

What is micturition?

Answer 17

urination

Question 18

What does the sympathetic branch do in micturition?

Answer 18

-relaxes the muscles of the bladder so that it can become full and closes the internal sphincter which is made of smooth muscle meaning it is under involuntary control

Question 19

What does the parasympathetic branch do in micturition?

Answer 19

-it constricts the bladder to allow for urination and it relaxes both the internal smooth muscle sphincter and the external skeletal muscle sphincter

Question 20

What does the somatic nervous system do in micturition?

Answer 20

provides sensory awareness of the fullness of the bladder via the dorsal root ganglion and allows for voluntary control over the external sphincter of the bladder since it is skeletal muscle

Question 21

What is the enteric system and what is it responsible for?

Answer 21

-it is an offshoot of the sympathetic and parasympathetic branches and is responsible for more complex rhythmic motor movements observed in the digestive tract which is known as peristalsis

Question 22

What is the role of the parasympathetic branch in the enteric system?

Answer 22

-CN X the vagus nerve and the intermediate gray zone in the sacral spinal cord receive input and directly innervate the lining of the digestive tract which make them postganglionic neurons

Question 23

What is the role of the sympathetic branch on the enteric system?

Answer 23

-input comes from neurons in the prevertebral ganglia

Question 24

What are the two plexuses that comprise the entire enteric system and what is a plexus?

Answer 24

-myenteric plexus
-submucosal plexus
-bundle of nerves and blood and lymphatic tissue

Question 25

What is the role of the myenteric plexus?

Answer 25

controls the smooth muscle of the

Question 26

What is the role of the submucosal plexus?

Answer 26

controls secretions of chemicals for digestion