Autonomics - Basics

Question 1

What is the division between sympathetic and parasympathetic?

Answer 1

difference is anatomical in origin
sympathetic - thoracolumbar
parasympathetic - craniosacral

Question 2

Where are the ganglia of the sympathetic NS? Length of pre vs post-ganglionic neurons?

Answer 2

Ganglia in paravertebral chains; pre ganglionic fibers tend to be short and post ganglionic long

Question 3

Where are ganglia of parasympathetics? Length of fibers?

Answer 3

Ganglion cells distributed diffusely or in networks in walls of innervated organs. Long pre-ganglionic, short post-ganglionic

Question 4

What NT is used in all ganglia?

Answer 4

Ach

Question 5

What NT is used by post-ganglionic parasympathetics?

Answer 5

Ach - cholinergic

Question 6

What NT is used by most post-ganglionic sympathetics?

Answer 6

NE - adrenergic

Question 7

What are the three exceptions in the sympathetic nervous system?

Answer 7

sweat glands, renal vascular smooth muscle, and chromaffin cells in adrenal medulla

Question 8

What NT is used by sympathetics going to sweat glands?

Answer 8

Ach

Question 9

What NT is used by sympathetics going to renal vascular smooth muscle?

Answer 9

dopamine

Question 10

What happens with sympathetics going to the adrenal medulla?

Answer 10

Pre-ganglionic releases Ach on chromaffin cells which acts as specialized post-ganglionic neurons and release epi and NE into the blood

Question 11

Which branch of the ANS is more diffuse and which is more discrete?

Answer 11

Sympathetic - diffuse

parasympathetic - discrete

Question 12

Where is the enteric nervous system located?

Answer 12

walls of the GI tract

Question 13

What three things does the enteric nervous system receive input from?

Answer 13

preganglionic parasympathetics, postganglionic sympathetics, sensory input from within the wall of the gut

Question 14

Where is the output of the enteric nervous system directed? What does it affect?

Answer 14

To smooth muscle and secretory cells to control motility and secretion

Question 15

What’s the result of ligand binding to nicotinic receptors? How do the Nn and Nm differ?

Answer 15

differ in subunit composition (and sometimes in how many ligand binding sites);
ligand binding results in opening of Na and K channels and depolarization

Question 16

What’s the mechanism of M2 and M4 receptors?

Answer 16

Gi; inhibit adenylate cyclase and/or activate K channels (hyper polarization)

hyperpolarization of M2 causes slowing of heart, inhibition of neurotransmitter release

Question 17

What’s the mechanism of M1, M3, and M5 receptors?

Answer 17

Gq; activate phospholipase C, increasing DAG and IP3 (therefore Ca2+)

smooth muscle contration by M3
neuroregulation by M1

Question 18

What’s the mechanism of alpha-1 receptor?

Answer 18

Gq; activate PLC, leads to smooth muscle contraction

Question 19

What’s the mechanism of alpha-2 receptors?

Answer 19

Gi; decrease cAMP, hyperpolarize via K channel; leads to inhibitions of neurotransmitter release

Question 20

What’s the mechanism of the beta receptors?

Answer 20

all Gs; activate adenylate cyclase and increase cAMP
beta-1 - increase in force and rate of heart
beta-2 - smooth muscle relaxation
beta-3 - increase lipolysis

Question 21

Autoreceptors are often used in presynaptic regulation. Are they generally excitatory or inhibitory?

Answer 21

inhibitory; inhibit further release of that NT

Question 22

What are receptors on the presynaptic terminal that respond to NT other than that released by that neuron and exert control on NT release called?

Answer 22

heteroreceptors

Question 23

What are possible sites of therapeutic opportunity?

Answer 23

NT synthesis, storage, release, termination

receptors on postsynaptic cells

Question 24

What are the steps in the synthesis of catecholamines? Note important locations where appropriate.

Answer 24

tyrosine -> L-DOPA (rate-limiting step)
L-DOPA -> dopamine
dopamine -> norepi (occurs in vesicles)
norepi -> epi (in adrenal medulla)

Question 25

Differences in norepi and epi.

Answer 25

norepi = neurotransmitter; action in synapse
epi = neurohormone; released into vasculature by adrenals to have effect

Question 26

What are the three ways that norepi effect is terminated?

Answer 26

Uptake 1 - ‘re-uptake’ neuron specific, high specificity, low capacity
Uptake 2 - extra-neuronal (ie by effector cell); non-specific, high capacity; how most drugs will be processed
Diffusion away into capillaries, etc

Uptake 1 is the primary mechanism!!! Uptake 2 is a lesser role

Question 27

What are the major metabolic enzymes for epi and norepi? Where are they located?

Answer 27

MAO - monoamine oxidase; located on mitochondria surface

COMT - catechol-O-methyl transferase; located in cytoplasm of many cells, notably liver

Question 28

Agonist (ISO, Epi, NE, DA, CLON) at adrenergic receptors.

Answer 28

beta1 - ISO>Epi>=NE>DA
beta2 - ISO>Epi»NE»DA
alpha1 - Epi>=NE>DA»ISO
alpha2 - CLON>Epi>=NE»ISO