MMT: Introduction to the ANS

Question 1

Break down the nervous system, starting with the two major divisions and branching out

Answer 1

Question 2

Briefly describe the role of the autonomic nervous system in our bodies

Answer 2

The ANS innervates almost every organ/tissue in the body and helps maintain homeostasis in response to changing environments

Question 3

What are the main targets of autonomic nervous system?

Answer 3

Cardiac muscle, smooth muscle, and glands

Question 4

Most tissues in the body are dually innervated by sympathetic and parasympathetic nervous systems. What are the big exceptions?

Answer 4

Blood vessels and sweat glands are only innervated by the sympathetic nervous system

Question 5

compare the organization of the SNS and PSNS

Answer 5

In the PSNS, the long preganglionic fibers synapse onto an autonomic ganglion near the effector organ. The short postganglionic fiber leaves the ganglion and travels to the effector organ.

In the SNS, the short preganglionic fiber synapses onto an autonomic ganglion in the sympathetic trunk. A long postganglionic fiber leaves the ganglion and travels to the effector organ.

Question 6

What is another name for the parasympathetic nervous system? Why?

Answer 6

Craniosacral; preganglionic fibers originate from the brainstem or sacral region of the spinal cord

Question 7

What is another name for the sympathetic nervous system? Why?

Answer 7

Thoracolumbar; preganglionic fibers originate from the thoracic or lumbar spine (T1-L2/3)

Question 8

identify the neurotransmitters released by fibers in the SNS and PSNS

Answer 8

PSNS: preganglionic and postganglionic both release acetylcholine

SNS: preganglionic releases acetylcholine, postganglionic releases norepinephrine

Question 9

What ion channels are involved in action potentials moving along preganglionic fibers, and the fiber synapsing onto a ganglion?

Answer 9

In a preganglionic fiber, signals are propagated via voltage gated sodium channels. The preganglionic fibers able to synapse due to voltage gated calcium channels.

Question 10

Which division of the nervous system is considered all or nothing? Why?

Answer 10

Sympathetic; one preganglionic fiber can synapse on multiple postganglionic fibers

Question 11

Which division of the nervous system is considered to have discrete output? Why?

Answer 11

The PSNS; most of the ganglia are set up in a 1:1 ratio, meaning one preganglionic fiber synapses on one postganglionic fiber.

Question 12

In what instance does the sympathetic nervous system utilize acetylcholine in postganglionic fibers?

Answer 12

When it is targeting the adrenal medulla or sweat glands.

Question 13

What is released by the adrenal medulla in response to sympathetic innervation?

Answer 13

Epinephrine (hormone) and some norepinephrine (neurotransmitter) into the bloodstream

Question 14

What are major control points of the ANS?

Answer 14

Hypothalamus and medulla

Question 15

How does the body measure volume in vessels?

Answer 15

Via the stretching and mechano and chemosensory receptors; in response to stretch or lack thereof, these receptors send signals to the brain and ultimately impact activity of the SNS

Question 16

What is the primary neurotransmitter used at the neuromuscular junction?

Answer 16

acetylcholine

Question 17

Cholinergic drugs target ___ receptors in the ___

Answer 17

acetylcholine; PSNS

Question 18

adrenergic drugs target ___ receptors in the ___

Answer 18

NE; SNS

Question 19

What are the two major classes of cholinergic receptors? What are their methods of action?

Answer 19

Muscarinic: GPCRs
Nicotinic: ion channels that are permeable to cations, particularly Na.

Question 20

What are the two primary subtypes associated with nicotinic receptors

Answer 20

Nn: neuronal nicotinic that are present in ganglia

Nm: neuromuscular nicotinic present in neuromuscular junction

Question 21

Describe where muscarinic receptors will be found

Answer 21

All PSNS effector sites, CNS, and some SNS effector sites

Question 22

Describe where nicotinic receptors will be found

Answer 22

All ANS ganglia, adrenal medulla, neuromuscular junction, and CNS

Question 23

What receptor type will always be found at the synapse between the preganglionic fiber and the ganglion? Why?

Answer 23

Nicotinic acetylcholine receptors; they’re ligand-gated ion channels that allow for depolarization of the membranes and thus further synapsing onto a postganglionic fiber

Question 24

Describe basic impacts of the SNS

Answer 24

Raised epinephrine
raised heart rate, conduction velocity, contractility, and cardiac output
increased blood flow to skeletal muscle
dilation of pupils
dilation of bronchioles
relaxed bladder and tightened sphincter to inhibit urination
lowered GI motility and digestion
increased blood glucose
increased sweating

Question 25

Describe the basic impacts of the PSNS

Answer 25

lowered heart rate, conduction velocity, contractility, and cardiac output
increased blood flow to GI tract
contraction of pupils
constriction of airways
increased bladder tone and loosened sphincter to allow urination
raised GI motility and digestion
increased salivation
stimulated tear production