Autonomics I

Question 1

What is the anatomic division of the autonomic nervous system? Where are ganglia generally located with respect to each division? Are the two divisions normally opposing or cooperative? What is an example of cooperative input?

Answer 1

Sympathetic (Thoracocolumbar), Parasympathetic (craniosacral). S: Close to spinal column, P: Closer to/w/i target organ; Generally opposing; Salivary Glands

Question 2

All preganglionic fibers use what neurotransmitter? Post ganglionic parasympathetic fibers use what neurotransmitter? All post ganglionic sympathetic fibers use what NT?

Answer 2

Acetylcholine; acetylcholine; norepinephrine

Question 3

Are all postganglionic sympathetic fibers adrenergic? If not, what are some exceptions?

Answer 3

NO! Sweat glands have ACh muscarinic receptors, Renal vascular smooth muscle has Dopamine receptors, Chromaffin cells are specialized post-ganglionic cells that have neuronal nicotinic ACh receptors

Question 4

What are typical roles of ACh? NE?

Answer 4

Primary NT at ANS ganglia, somatic NMJ, and at parasympathetic postganglionic nerve endings. Primary excitatory transmitter for smooth muscle, secretory cells, and nerve to nerve transmission in ENS; Primary transmitter at most sympathetic postgang nerve endings

Question 5

What is a cholinergic nerve terminal?

Answer 5

Nerve terminal that releases ACh.

Question 6

What is a noradrenergic nerve terminal?

Answer 6

Nerve terminal that releases NE.

Question 7

What are the similarities between cholinergic and noradrenergic nerve terminals? Differences?

Answer 7

Both have similar synthesis and release of NTs. Different handling after release of NTs. Cholinergic: AChesterase degrades ACh and returns Ch to nerve. Noradrenergic: NE diffuses, reuptakes, metabolized.

Question 8

Are drugs that inhibit ACh synthesis useful? Why? NE? Why? What is the best drug target? Why

Answer 8

No, they are non-specific and therefore not useful (except Botox); Yes, more specific; Target tissue receptors allow for selectivity.

Question 9

In postganglionic autonomic ganglia, what type of receptors exist? Are they good drug targets? Are they the same receptors that are on muscles?

Answer 9

Neuronal Nicotinic (NN) receptors. No because NN receptors exist for Symp and Parasymp. They are not the same. Muscles have NM receptors.

Question 10

What is the ligand for Muscarinic Receptors? Adrenergic Receptors? Nicotinic Receptors?

Answer 10

ACh, NE, ACh

Question 11

General Mechanism of M1, 2, 3 receptors

Answer 11

ACh -> Gq protein -> IP3, DAG Ca2+ increase ->sm. muscle contraction (M3), neuroregulation (M2)

Question 12

General Mechanism of M2, 4 receptors

Answer 12

ACh -> Gi protein -> open K+ channel -> depolarization -> slow heart rate and inhibition of neurotransmitter release by M2 autoreceptors (which are on nerve terminals)

Question 13

General Mechanism of Alpha1 receptor

Answer 13

NE -> Gq protein -> IP3, DAG, Ca2+ increase -> sm. musc contraction

Question 14

General Mechanism of Alpha2 receptor

Answer 14

NE -> Gi protein -> open K+ channel -> depolarization -> inhibition of NT release

Question 15

General Mechanism of Beta1, 2, 3 receptors

Answer 15

NE -> Gs -> cAMP increase -> Beta 1: Increase force and rate of heart contraction, Beta 2: Smooth muscle relaxation, Beta 3: Lipolysis

Question 16

At what three levels are the ANS integrated?

Answer 16

Central, Presynaptic, Postsynaptic

Question 17

Describe CNS integration of ANS in blood pressure

Answer 17

Increase in BP results in baroreceptors firing resulting in decrease in Renin and Sympathetic Outflow. Decrease BP would result in increased sympathetic outflow, renin release, and decreased parasympathetic outflow.

Question 18

Describe two methods of presynaptic integration of ANS in blood pressure control

Answer 18

1) NE from noradrenergic presynaptic nerve termials acts on Alpha2 autoreceptors performing a negative feedback loop and decreasing NE output. 2) Some vagal fibers release ACh onto sympathetic nerve terminals via presynaptic M2 receptors and inhibit NE release

Question 19

Describe postsynaptic ANS integration.

Answer 19

A postsynaptic nerve can have both Muscarinic and Nicotinic receptors resulting in EPSPs and IPSPs.