Autonomic Nervous System I

Question 1

What effects does the sympathetic nervous system have on the heart?

Answer 1

Stimulation of HR at the SA node (pos chronotropic). Stimulation of AV nodal conduction (pos dromotropic). Stimulate ventrical myocardial contractility (pos ionotropic)

Question 2

What effects does the parasympathetic nervous system have on the heart?

Answer 2

Inhibition of HR at the SA node (neg chronotropic). Inhibitiong of AV nodal conduction (neg dromotropic). Inhibition of atrial contractility with strong stim. (neg ionotropic)

Question 3

The SNS activates what receptor types in the heart?

Answer 3

Beta-1 adrenergic receptors. (Propranolol is an antagonist and is used to treat hypertension and tachycardia.)

Question 4

The property of divergence is a characteristic of which division of the ANS? What does it allow?

Answer 4

The SNS. It allows a widespread response of numerous effectors when physiologically necessary. Average pregang axon contacts ~100 postgang (PNS 15-20)

Question 5

En Passant synapses (varicosities) are characteristic of what?

Answer 5

The ANS. They permit a single axon to have broad actions in target tissues.

Question 6

Somatic neurons exhibit a monosynaptic pathway. The neuron releases Ach which binds to what receptor?

Answer 6

N1 nicotinic cholinergic receptors on the postsynaptic membrane of skeletal muscle cells.

Question 7

What is an N1 receptor antagonist? How about an agonist?

Answer 7

d-tubocurarine. Nicotine

Question 8

In the PNS and SNS preganglionic neurons release Ach. What does it bind to?

Answer 8

N2 nicotinic cholinergic receptors on the postsynaptic membrane of the postganglionic neuron

Question 9

What is an N2 receptor antagonist?

Answer 9

Hexamethonium

Question 10

SNS target tissues express what types of receptors?

Answer 10

Adrenergic receptor subtypes; Alpha 1 and 2 Beta 1 and 2. As well as, muscarinic cholinergic receptors (in sweat glands only)

Question 11

PNS target tissues express what types of receptors?

Answer 11

Various combination of 5 muscarinic cholinergic receptors M1 - M5

Question 12

Explain the mechanism of action of alpha1 adrenoreceptors

Answer 12

Norepinephrine binds leading to activation of the Gq protein. That activates phospholipase C with clips PIP2 into DAG and IP3. IP3 causes calcium release while DAG stimulates protein kinase C

Question 13

Explain the mechanism of action of Beta1 and 2 adrenoreceptors

Answer 13

Norepinephrine binds leading to activation of the Gs prtein. The activated alpha subunit activates adenylyl cyclase which converts ATP to cAMP.

Question 14

Explain the mechanism of action of nicotinic cholinergic receptors

Answer 14

2 ACh bind to the alpha subunits of the receptors and open a Na+ K+ channel. They are GPCRs and M1, M3, M5 act like alpha1 adrenergic receptors with PLC, IP3 and DAG. M2 and M4 inhibit adenylate cyclase and oppose Beta receptors

Question 15

What inhibis M1, M3, and M5 muscarinic receptors?

Answer 15

Atropine

Question 16

What inhibits M2 and M4 muscarinic receptors?

Answer 16

Atropine

Question 17

ACh activates which receptors?

Answer 17

N1 nicotinic, N2 nicotinic, M1-M5 muscarinic

Question 18

Epinephrine binds to which receptors with greater affinity?

Answer 18

Beta 1, 2, 3

Question 19

Norepinephrine binds to which receptors with greater affinity?

Answer 19

Alpha 1 and 2, however, they can be equal in affinity to epi.

Question 20

Epi effects are more prominent in targets where Beta-adrenergic receptors predominate what are these target tissues?

Answer 20

The heart, lungs, and liver.

Question 21

Where do norepi effects predominate?

Answer 21

The vasculature; where alpha adrenergic receptors are expressed.

Question 22

What is pheochromocytoma? What are the symptoms?

Answer 22

Neoplams of the adrenal medulla. Secretion of excessive amounts of norepi, or sometimes epi, or both. Sustained hypertension, cold hands and feet, sweating, and feeling hot are symptoms.

Question 23

What is Horner syndrome? What does it cause?

Answer 23

Injury to SNS produces ipsilateral miosis, ptosis, and anhidrosis.