Autonomics - Basics

Question 1

What is the main goal of the ANS?

Answer 1

Maintain homeostasis

Question 2

How many synapses are found in ANS organ signals? What NTs or hormones are used for signaling?

Answer 2

2! Preganglionic - ACh

Postganglionic - ACh (little branching), NE (lots of branching), or Dopamine (systemic effect)

Question 3

What are the exceptions of sympathetic innervated organs that use ACh in postganglionic transmission?

Answer 3

Sweat glands, chromaffin cells in adrenal medulla

Question 4

What uses dopamine as a postganglionic sympathetic signal?

Answer 4

Renal vascular smooth muscle

Question 5

What is the differences in the handling of ACh and NE after it has been released from the presynaptic terminal (i.e. describe uptake)

Answer 5

ACh: broken down by AChE to acetate and choline. Choline goes back into presynaptic terminal and is reused.

NE: goes through diffusion, uptake, and metabolism in liver

Question 6

What kind of ACh receptor is found in the ganglion of both the SNS and PNS?

Answer 6

Neuronal Nicotinic receptor (Nn)

Question 7

What kind of ACh receptor is found in the target organs of the PNS

Answer 7

Muscarinic (M)

Question 8

Why can nicotinic receptors respond so rapidly?

Answer 8

Ligand gated ion channel

Question 9

Why are muscarinic receptors and adrenergic receptors slower to respond?

Answer 9

G protein coupled receptors that activate 2nd messengers

Question 10

What second messengers do M1, M3, and M5 activate, and what is their downstream effect?

Answer 10

Gq

Downstream increase of DAG + IP3, which INCREASES Ca!

M3 : smooth muscle contraction

M1 : neuroregulation

Question 11

What second messengers do M2 and M4 activate, and what is their downstream effect?

Answer 11

Gi

decreases cAMP,
opens K channel for a hyperpolarizing effect

M2 : slowing of HR and inhibition of NT release

Question 12

What second messengers do α1 receptors activate? Downstream effects?

Answer 12

Gq

Increase Ca

Smooth muscle contraction!

Question 13

What second messengers do α2 receptors activate? Downstream effects?

Answer 13

Gi

decreases cAMP, hyperpolarizes

Inhibition of NT release

Question 14

What second messengers do β1, β2, and β3 receptors activate? What are the downstream effects

Answer 14

Gs

increases cAMP

β1 : increase in force/rate of heart contractions

β2 : smooth muscle relaxation

β3 : lipolysis

Question 15

By which receptors can negative feedback in a synaptic terminal occur?

Answer 15

M2, α2

Question 16

What are some disadvantages of cholinomimetics?

Answer 16

ACh has multiple sites of action, both in the SNS and PNS so it can produce very diffuse and nonspecific effects