Physiology of the Autonomic Nervous System

Question 1

Characteristic of parasympathetic ganglion:

Answer 1

Craniosacral, near target organ (viscera), long pre-ganglionic tracts, short post ganglionic tract (on the viscera already)

Question 2

Characteristic of sympathetic ganglion:

Answer 2

Thoracolumbar, forms the sympathetic chain, short pre synaptic tracts, long post synaptic tracts

Question 3

Describe the reflex arc:

Answer 3

Afferent fiber senses information > relays that info to the CNS (spinal cord, so it’s fast) > in the spinal cord, the afferent neuron synapses to the efferent neuron > efferent neuron synapses to the skeletal muscle to act

Question 4

How can viscera detect sensory information/what acts as the afferent neuron?

Answer 4

Baroreceptors, chemoreceptors etc.

Question 5

Where are autonomic responses processed?

Answer 5

Hypothalamus (spinal cord is for the somatic nervous system)

Question 6

What acts as the response neuron/motor neuron for the viscera?

Answer 6

The autonomic nervous system (parasympathetic/sympathetic fibers)

Question 7

Describe the autonomic reflex arc:

Answer 7

From the CNS, the presynaptic neuron synapses on the post synaptic neuron, which will in turn synapse to the viscera to do something

Question 8

Difference between the somatic and autonomic reflex arc:

Answer 8

Somatic system has a 2 neuron system (spinal cord motor neuron synapses directly to the skeletal muscle) while the autonomic system has a post ganglionic neuron between the pre-ganglionic and the viscera. So synapse 1 will be at the ganglion and synapse 2 will be at the viscera

Question 9

Is the first synapse the same in the sympathetic and parasympathetic nervous systems?

Answer 9

Yes, both involve Acetylcholine release at the synaptic cleft

Question 10

What receptors receive Acetylcholine at the first synapse (between the pre and post synaptic ganglion)?

Answer 10

Nicotinic Cholinergic receptors (nAchRs)

Question 11

*What are varicosities?

Answer 11

Vesicles at nerve terminals that contain the neurotransmitters to release to visceral muscle fibers.

Question 12

How are the post synaptic receptors differently arranged in visceral tissue compared to skeletal muscle?
How are they similar?

Answer 12

• The ligand gated receptors are more spread out and not concentrated at the post synaptic terminal like the NMJ.
• Ca2+ still needed to release the neurotransmitters into the visceral tissue post action potential

Question 13

What is the neurotransmitter released at synapse 2 of the parasympathetic branch?

Answer 13

Acetylcholine

Question 14

*What receptors at the target visceral cells receive parasympathetic signals?

Answer 14

Muscarinic cholinergic receptors (mAchRs)

-except chromaffin cells

Question 15

Muscarinic receptors are activated by ….

Answer 15

Acetylcholine and muscarine (exogenous chemical)

Question 16

What type of receptors are mAchRs?

Answer 16

Metabotropic (serpentine) receptor family

GPCR/second messenger type

Question 17

M1R (muscarinic receptor 1)

Answer 17

-CNS (not autonomic), has role in memory
Functions: increase secretion of salivary glands and acid secreting cells in the stomach

Memory drools acid

Question 18

M3R (muscarinic receptor 3)

Answer 18

Functions: contraction of smooth muscle cells
Secretion of exocrine glands

Duct and digest

Question 19

M2R (muscarinic receptor 2):

Answer 19

Slow heart rate on cardiac muscle, (acts on K+ channels by opening the channels so the cell hyperpolarizes and stops contracting)
-also lowers cAMP

cAMP the fuck down please, K?

Question 20

What neurotransmitter is at synapse 2 (post synaptic to viscera) in the sympathetic branch?

Answer 20

Norepinephrine (epinephrine released by nerves)

Question 21

What receptors on visceral cells receive sympathetic signals?

Answer 21

Adrenergic receptors

Question 22

Alpha Adrenergic receptors

Alpha 1 Receptors

Answer 22

Gq coupled
Leads to increased Ca2+ intracellularly
Functions: smooth muscle contraction, increase pro-glucagon pathways in liver and adipose tissues, reduce watery secretion in lacrimal glands, contract iris (which in turn dilates pupil)

VGLD (Very good looking dog)

Question 23

Alpha adrenergic receptors

Alpha 2 Receptors:

Answer 23

Gi coupled
Leads to decreased cAMP/adenylate cyclase activity
Functions: contracts GI sphincters, increase glucagon/decrease insulin in pancreas, vasoconstriction increase clotting via platelets

SVGP (Some very good pizza)

Question 24

Beta Adrenergic receptors:

Beta1 - adrenergic receptors

Answer 24

Gs coupled
Leads to increased cAMP/adenylate cyclase activity
Functions: increase HR at SA node, Increase contraction strength at ventricle of heart, viscous secretion of salivary glands, lipolysis of adipose tissue

Pouding heart burns fat

Question 25

Beta Adrenergic Receptors

Beta 2 - adrenergic receptors

Answer 25

Gs couple
Leads to increased cAMP/adenylate cyclase
Functions: relaxation of smooth muscle at respiratory, GI, GU and vascular systems. Liver glycogenolysis, relaxation of ciliary muscle = flattening of lens in the eye

Block GIGU, flatten lens

Question 26

Beta Adrenergic receptors

Beta 3 adrenergic receptors

Answer 26

Gs coupled
Leads to increased cAMP/adenylate cyclase
Functions: lipolysis of white adipose tissue and heat production from brown adipose tissue

burn both kinds of fat

Question 27

Adrenal medulla and the sympathetic system:

Answer 27

Preganglionic fiber to the adrenal medulla goes straight to synapse on the medulla and not to another neuron. Ach released on the nAchRs on the chromaffin cells in the medulla. Chromaffin cells make and release epi into the blood.
-Basically this synaptic system has a nerve component: acetylcholine at the synapse and a blood component - epinephrine from chromaffin cells

Question 28

Describe the parasympathetic state:

Answer 28

Plenty of oxygen
Heart beating slowly
BP low
Energy going to digesting food, so blood goes to intestines
Getting energy from the food being digested

Question 29

Describe the sympathetic state:

Answer 29

Need lots of oxygen (running from a bear)
O2 goes to muscle
Heart pumping fast and hard
Digesting goes to the back burner since we need to run from the bear
Use up stores so we can use it for energy to run from the bear