Autonomic nervous system and neurotransmission

Question 1

Autonomic nervous system definition

Answer 1

Effector system that controls viscera

Question 2

Functions of the autonomic nervous system

Answer 2

Maintain homeostasis and respond to external stimuli

Question 3

Subdivision of the ANS

Answer 3

Sympathetic, parasympathetic, and enteric

Question 4

Major neurotransmitters in the ANS

Answer 4

Acetylcholine and norepinephrine

Question 5

Other NT’s in the ANS

Answer 5

ATP, nitrous oxide, serotonin, GABA, dopamine, and glutamate

Question 6

Differences between ANS synapses and CNS synapses

Answer 6

ANS are not as well-defined, have variable synaptic cleft distances, and are all metabotropic

Question 7

Synthesis/degradation of NE

Answer 7

Synthesized in vesicles from Dopa, degraded in the cytosol by MAO and COMT (also some degradation enzymes in the mitochondria and in circulation)

Question 8

NE release

Answer 8

Occurs somewhat near the target cell, but is not closely coupled

Question 9

ACh synthesis and degradation

Answer 9

Synthesized by/broken back down to choline in the cytosol. Broken down by acetylcholinesterase

Question 10

Choline is found frequently in these foods

Answer 10

Egg yolks, liver, and soybeans

Question 11

Mechanism of nerve agents

Answer 11

Inhibit AChE and prevent ACh degradation, causing rapid death by overstimulation

Question 12

Treatment for nerve gas agents

Answer 12

Drug cocktail with Diazepam to prevent seizures, atropine to block muscarinic AChRs, and pralidoxime (2PAM) to recover AChE function

Question 13

Location of both ganglionic neurons

Answer 13

Preganglionic is within the CNS and synapses with a postganglionic neuron in an autonomic ganglion

Question 14

All preganglionic neurons secrete ___

Answer 14

acetylcholine

Question 15

Basal tone

Answer 15

Target organs have a resting level of activity that permits both increases and decreases from that set point.

Question 16

Location of preganglionic somas

Answer 16

Lateral horn in the thoracic and upper lumbar segments of the spinal cord and in the C8 segment (thoracolumbar)

Question 17

Type of receptors in the preganglionic-postganglionic synapse

Answer 17

Nicotinic (ionotropic, fast-acting)

Question 18

ANS: ipsilateral or contralateral?

Answer 18

Mostly ipsilateral, except for the intestines and pelvis, which are bilateral

Question 19

Two types of ganglia in the ANS

Answer 19

Paravertebral (sympathetic) and prevertebral (parasympathetic)

Question 20

Path of preganglionic neurons in the sympathetic system

Answer 20

Go usually into the ganglion at the corresponding level, but they can travel up and down. Enter through the white communicating ramus

Question 21

Superior cervical ganglion

Answer 21

Fused paravertebral ganglia from C1-C4 that control the head and neck

Question 22

Middle cervical ganglion

Answer 22

Fused paravertebral ganglia from C5-C6 that control the heart, lungs, and bronchi

Question 23

Stellate ganglion

Answer 23

Fused paravertebral ganglia from C7-C8 (T1) that also control the heart, lungs, and bronchi

Question 24

Gray communicating ramus

Answer 24

Postganglionic neurons send out their axons to spinal nerves through these

Question 25

Sympathetic postganglionic fibers secrete ___ and activate ___ ___ receptors in target organs

Answer 25

Norepinephrine, metabotropic adrenergic

Question 26

The special case of the adrenal medulla

Answer 26

Preganglionic axons pass through the splanchnic nerve and directly synapse with the medulla, so it doesn’t have a post-ganglionic neuron

Question 27

Chromaffin cells

Answer 27

Cells in the adrenal medulla that secrete epinephrine and NE directly into the blood stream as a response from the direct activation from cholinergic pre-ganglionic fiber

Question 28

The adrenal medulla is responsible for the secretion of __% of epinephrine and __% of norepinephrine into the circulation

Answer 28

80% and 20%

Question 29

Metabotropic receptors are coupled to these

Answer 29

G protein cascade

Question 30

Exception to the sympathetic activation of postganglionic adrenergic receptors

Answer 30

Sweat glands - innervated by the sympathetic branch, but are activated via ACh binding to muscarinic metabotropic receptors

Question 31

Location of parasympathetic preganglionic fibers

Answer 31

Cranial nerves in the brainstem and in the S3 and S4 sacral divisions of the spinal cord

Question 32

Which cranial nuclei contain preganglionic somas?

Answer 32

Cranial nerves II, VII, IX, and X.

Question 33

Type of receptors in parasympathetic post-ganglionic cells

Answer 33

Nicotinic (fast, ionotropic)

Question 34

Parasympathetic ganglia are typically close to or far away from their target organs?

Answer 34

Close to

Question 35

Parasympathetic postganglionic fibers typically activate these types of receptors with this NT

Answer 35

Metabotropic, ACh

Question 36

Important muscarinic receptors

Answer 36

M1 - gastric secretion

M2/M3 - smooth muscle function

Question 37

Parasympathetic smooth muscle activation generally causes ___, except . . .

Answer 37

dilation, except GI, where it causes contraction

Question 38

Parasympathetics of the glossopharyngeal

Answer 38

Baroreceptor afferent fibers from the carotid sinus, which go through the nucleus solitarius and eventually control heart rate and blood pressure

Question 39

Afferent fibers use this as their preferred nuerotransmitter

Answer 39

Glutamate

Question 40

Common neuromodulators

Answer 40

Angiotensin II, arginine vasopressin, substance P, enkephalin, oxytocin, somatostatin, vasoactive intestinal polypeptide

Question 41

Definition of referred pain

Answer 41

Pain in the viscera that is perceived by the CNS as somatic pain

Question 42

Why does referred pain happen?

Answer 42

Convergence of somatic and visceral afferent fibers from the same SC level

Question 43

Baroreceptor reflex

Answer 43

Negative feedback loop that controls arterial pressure

Question 44

Location of baroreceptors

Answer 44

Nerve terminals in the carotid sinus and the aorta

Question 45

Where afferent baroreceptor fibers end

Answer 45

Vasomotor and cardioregulatory centers of the medulla in the brainstem

Question 46

Effect of stimulation of the vasomotor and cardioregulatory centers

Answer 46

• Decrease in sympathetic input to the heart
• Increase in parasympathetic input
• Decrease of sympathetic input to vascular smooth muscle
• Decreased sympathetic input to adrenal chromaffin cells