Chr. 15 - The Autonomic Nervous System

Question 1

[15.1] What is the somatic nervous system?

Answer 1

The nervous system innervating skeletal muscles.

Question 2

[15.1] What is the autonomic nervous system?

Answer 2

The part of the nervous system regulating cardiac muscle, smooth muscle, and glands.

Question 3

[15.1] What is a visceral effector?

Answer 3

Any tissue of cardiac muscle, smooth muscle, or glands innervated by the ANS

Question 4

[15.1] What is biofeedback?

Answer 4

Information of a body function displayed by monitoring devices.

Question 5

[15.1] What are interoceptors?

Answer 5

Sensory receptors located in blood vessels, visceral organs, muscles, and the nervous system that monitor the internal environment.

Question 6

[15.1] What are the branches of the autonomic nervous system?

Answer 6

The sympathetic, parasympathetic, and enteric.

Question 7

[15.1] What is dual innervation?

Answer 7

An arrangement of innervation of organs by both sympathetic and parasympathetic branches of the autonomic nervous system.

Question 8

[15.1] What is an autonomic ganglion?

Answer 8

A cluster of nerve bodies in the autonomic nervous system.

Question 9

[15.1] Describe an autonomic nerve pathway.

Answer 9

Comprised of two neurons:

The first, known as the preganglionic neuron, originates in the CNS where the cell body is found, with a myelinated axon running down into an autonomic ganglion found in the PNS. Certain motor neurons can run to a chromaffin cell instead of a ganglion.

The second, known as the postganglionic neuron, originates in the ganglion and has an unmyelinated axon running from the ganglion to the effector.

Question 10

[15.1] What is a chromaffin cell?

Answer 10

A specialized cell in the adrenal medullae innervated by a preganglionic nerve. Secrete epinephrine and norepinephrine.

Question 11

[15.2] What is a preganglionic neuron?

Answer 11

A neuron with the cell body originating in the CNS and extending a myelinated axon to either an autonomic ganglion or a chromaffin cell.

Question 12

[15.2] What is a postganglionic neuron?

Answer 12

A neuron with the cell body originating in the autonomic ganglion synapsing with one or more preganglionic neurons, and extending its unmyelinated axon to a visceral effector.

Question 13

[15.2] What is the thoracolumbar division?

Answer 13

The preganglionic neurons of the sympathetic division with cell bodies originating in the lateral horns of the grey matter of T1-12 and L1/2.

Question 14

[15.2] What is the thoracolumbar outflow?

Answer 14

Specifically the axons of the thoracolumbar division.

Question 15

[15.2] What is the craniosacral division?

Answer 15

The preganglionic neurons of the parasympathetic division with cell bodies originating in cranial nerves III, VII, IX, X, as well as lateral grey matter of S2-4.

Question 16

[15.2] What is the craniosacral outflow?

Answer 16

Axons of the craniosacral division.

Question 17

[15.2] What are the groups of autonomic ganglia?

Answer 17

Sympathetic ganglia and parasympathetic ganglia.

Question 18

[15.2] List and describe the types of sympathetic ganglia.

Answer 18

Sympathetic trunk ganglia, either side of the vertebral column that innervate organs above the diaphragm.

Prevertebral ganglia, found anterior to the vertebral column close to abdominal arteries and innervate organs below the diaphragm.

Question 19

[15.2] What are terminal ganglia?

Answer 19

Ganglia of the parasympethic (or craniosacral) division. Located close to or within visceral organs.

Question 20

[15.2] What are autonomic plexuses?

Answer 20

Sympathetic and parasympathetic neurons forming tangled networks typically lying along major arteries.

Question 21

[15.2] List major plexuses and their location.

Answer 21

Cardiac plexus, thorax.
Pulmonary plexus, thorax.
Celiac plexus, abdomen.
Superior mesenteric plexus, abdomen.
Inferior mesenteric plexus, abdomen.
Hypogastric plexus, abdomen.
Renal plexus, abdomen.

Question 22

[15.2] What is a white ramus?

Answer 22

A short pathway through which a myelinated preganglionic neuron of the sympathetic division passes through.

Question 23

[15.2] What are the white rami communicantes?

Answer 23

The collective term for all white rami.

Question 24

[15.2] How many sympathetic trunk ganglia are there in each section of the vertebral column?

Answer 24

3 cervical
11 or 12 thoracic
4 or 5 lumbar
4 or 5 sacral
1 coccygeal.

Question 25

[15.2] What are the divisions of cervical ganglia and which regions do they innervate?

Answer 25

Superior cervical ganglia, innervate visceral effectors of the head and heart.

Middle cervical ganglion, innervate the heart and blood vessels of: the neck, shoulder, and upper limb.

Inferior cervical ganglion, innervate the heart and blood vessels of: the neck, shoulder, and upper limb.

Question 26

[15.2] How do axons leave the sympathetic trunk?

Answer 26

Entering spinal nerves,

Form cephalic periarterial nerves,

Form sympathetic nerves,

Form splanchnic nerves.

Question 27

[15.2] Describe how sympathetic postganglionic neurons enter spinal nerves.

Answer 27

Axons enter a pathway known as the grey ramus and merge with the anterior ramus of a spinal nerve.

Question 28

[15.2] Describe how cephalic periarterial nerves are formed.

Answer 28

Postganglionic neurons leave the sympathetic ganglion of the trunk and extend into the head, following arteries and innervating visceral effectors.

Question 29

[15.2] Describe how sympathetic nerves are formed.

Answer 29

By postganglionic axons leaving the sympathetic trunk and extending to their destination of innervation.

Question 30

[15.2] Describe how splanchnic nerves are formed.

Answer 30

Sympathetic preganglionic axons pass through the sympathetic trunk without terminating within it. Once beyond, they are known as splanchnic nerves and synapse with sympathetic postganglionic neurons.

Question 31

[15.2] What are the types of splanchnic nerves?

Answer 31

Splanchnic nerves that run to the abdominopelvic organs, and splanchnic nerves to run to the adrenal medulla.

Question 32

[15.2] What is the difference between the types of splanchnic nerves?

Answer 32

Splanchnic nerves to the abdominopelvic organs synapse with postganglionic neurons before reaching the viscera.

Splanchnic nerves to the adrenal medulla do not synapse with postganglionic neurons; instead they run directly to chromaffin cells.

Question 33

[15.2] Describe the structure of the parasympathetic division.

Answer 33

Cell bodies of parasympathetic neurons originate in two places: the brainstem, and exit as part of a cranial nerve; and in the grey matter of S2-4 of the spinal cord, exiting as part of the anterior root.

Question 34

[15.2] What is the cranial parasympathetic outflow?

Answer 34

The axons of preganglionic neurons extending from the cranial nerves.

Question 35

[15.2] What is the sacral parasympathetic outflow?

Answer 35

The axons of the preganglionic neurons extending from the grey matter of S2-4

Question 36

[15.2] What are the ganglia within the cranial outflow?

Answer 36

Ciliary, pterygopalatine, submandibular, otic, and “ganglia associated with vagus X nerve.”

Question 37

[15.2] Describe the ciliary ganglia.

Answer 37

Lie lateral to the optic III nerve, postganglionic axons innervate smooth muscle of the eye.

Question 38

[15.2] Describe the pterygopalatine ganglia.

Answer 38

Located lateral to sphenopalatine foramen. Receive axons from facial VII nerve. Postganglionic axons innervate nasal mucosa, palate, pharynx, and lacrimal glands.

Question 39

[15.2] Describe submandibular ganglia.

Answer 39

Located near ducts of submandibular salivary glands. Innervate submandibular and sublingual salivary glands.

Question 40

[15.2] Describe the otic ganglia.

Answer 40

Located inferior to foramen ovale, receive from glossopharyngeal IX nerves and innervate parotid salivary glands.

Question 41

[15.2] Describe ganglia associated with vagus X nerve.

Answer 41

Contain 80% of cranial outflow, extend to many terminal ganglia in thorax and abdomen. Innervates heart, airway, liver, gallbladder, stomach, pancreas, small intense, and a portion of large intestine.

Question 42

[15.2] What are pelvic splanchnic nerves?

Answer 42

Preganglionic axons originating in the sacral spinal column and extending to form terminal ganglia. Postganglionic neurons innervate smooth muscle and glands of the colon, ureters, urinary bladder, and reproductive organs.

Question 43

[15.3] What are the classifications of autonomic neurons based on neurotransmitters?

Answer 43

Cholinergic and adrenergic.

Question 44

[15.3] What is a cholinergic neuron?

Answer 44

Neurons that release acetylcholine as a neurotransmitter.

Question 45

[15.3] Which neurons within the ANS are cholinergic?

Answer 45

All preganglionic neurons, all parasympathetic postganglionic neurons, and most sympathetic postganglionic neurons innervating sweat glands.

Question 46

[15.3] Which types of cholinergic receptors exist?

Answer 46

Nicotinic and muscarinic.

Question 47

[15.3] Describe nicotinic receptors.

Answer 47

Receptors that bind acetylcholine but can be activated by nicotine. Present in plasma membranes of dendrites of both types of postganglionic neurons. Also found in chromaffin cells, and motor end plates of NMJs.

Question 48

[15.3] Describe muscarinic receptors.

Answer 48

Receptors that bind acetylcholine as well as a poison known as muscarine. Present in plasma membranes of effectors and innervated by parasympathetic postganglionic axons.

Question 49

[15.3] What is an adrenergic neuron?

Answer 49

Autonomic neurons that release norepinephrine.

Question 50

[15.3] Describe adrenergic receptors.

Answer 50

Receptors that bind both norepinephrine and epinephrine.

Question 51

[15.3] Which types of adrenergic receptors exist?

Answer 51

Alpha and beta receptors.

Question 52

[15.3] Which enzymes inactivate norepinephrine?

Answer 52

Monoamine oxidase and catechol-0-methyltransferase.

Question 53

[15.3] What is an agonist?

Answer 53

A substance that binds to and activates a receptor.

Question 54

[15.3] What is an antagonist?

Answer 54

A substance that binds to and blocks a receptor.

Question 55

[15.4] What is autonomic tone?

Answer 55

The balance between sympathetic and parasympathetic activity.

Question 56

[15.4] Describe the fight-or-flight response.

Answer 56

A stimulation of the sympathetic division and inhibition of the parasympathetic division.

Question 57

[15.4] Describe the rest-and-digest response.

Answer 57

An activation of the parasympathetic division and inhibition of the sympathetic division.

Question 58

[15.5] What is an autonomic reflex?

Answer 58

Responses that occur when a nerve impulse passes through an autonomic reflex arc.

Question 59

[15.5] What region of the brain primarily directs the ANS?

Answer 59

The hypothalamus.