regulation 3

Question 1

Sympathetic stimulation directly activates:

Answer 1

VSMC contraction

independent of membrane depolarization

Question 2

Sympathetic stimulation mechanism

Answer 2

1. Sympathetic terminals release NE
2. NE activates aARs on VSMCs
3. aARs in VSMCs are coupled to Gq
4. Gq activation causes IP3 production.
5. IP3 increases cytosolic Ca2+
   (by activating SR Ca2+ release via IP3 receptors)

Question 3

Minor case in skeletal muscle:

Answer 3

Circulating epinephrine can activate b2ARs on VSMCs,

This causes vasodilation through cAMP/PKA inhibition of MLCK.

Question 4

Baroreceptor reflex =

Answer 4

SHORT TERM and rapid negative feedback mechanism for sudden changes in blood pressure.

Question 5

Baroreceptors are

Answer 5

pressure-sensitive NEURONS

Question 6

High pressure baroreceptors

Answer 6

1. in aortic arch and carotid sinus

2. respond to increases in arterial pressure by increasing firing rate

Question 7

Stretch of arterial walls activates

Answer 7

mechanosensitive eNac Na+ channels on baroreceptor cell membranes.

Inward current causes depolarization, triggers APs in neurons

Question 8

Carotid sinus baroreceptors project to the:

Answer 8

“cardiovascular control center” in the medulla via glossopharyngeal nerve.

Question 9

Aortic arch baroreceptors project via the:

Answer 9

vagus nerve.

Question 10

Low pressure baroreceptors

Answer 10

1. in atria and vena cavae,

2. mediate “Bainbridge Reflex” (increase HR in response to stretch).

Question 11

CV control center Feedback response via

Answer 11

changes in autonomic regulation of the heart and vasculature

Question 12

Classic Baroreceptor Reflex

Answer 12

1. Increase in pressure increase firing rate of baroreceptors.
2. CV control centers decrease sympathetic and increase parasympathetic output.
3. In heart this causes decreases heart rate and inotropy.
4. In vasculature, decreased sympathetic tone causes vasodilation

Question 13

Intrinsic control of the vasculature

Answer 13

1. Vasoactive metabolites
2. Myogenic response
3. Nitric Oxide
4. Endothelin

Question 14

What is the primary mechanism to match blood flow in the capillaries to metabolic demand?

Answer 14

vasoactive metabolites

Question 15

Vasoactive metabolites produced by metabolically active tissue =

Answer 15

local feedback control of blood flow.

Question 16

Vasoactive metabolites will result in

Answer 16

1. decreased PO2
2. increased PCO2 (decreased pH), partially due to lactic acid
3. increased extracellular K+
4. increased adenosine

Question 17

How do vasoactive metabolites increase adenosine?

Answer 17

As a byproduct of ATP hydrolysis:

binds to A2 purinergic receptors on VSMCs. A2 receptors are GPCRs coupled to Gs = increased cAMP, vasodilation via inhibition of MLCK

Question 18

Stretch-activated ion channels of Trp family in VSMC membrane.

Answer 18

1. non-selective cation channels, many isoforms

2. inward current depolarizes cell, also direct Ca2+ entry = vasoconstriction, reduces flow

Question 19

Basal NO release helps set

Answer 19

resting vascular tone

Question 20

Nitric oxide is a major physiological mechanism for _____.

Answer 20

vasodilation

Question 21

NO action in VSMCs

Answer 21

1. NO diffuses across membranes to
2. VSMCs, where it activates guanylate cyclase to produce cGMP
3. cGMP activates PKG
4. PKG reduces intracellular Ca2+ via activation of SERCA, and inhibition of L-type Ca2+ channels
5. Decreased Ca2+ causes vasodilation via reduced MLCK activity

Question 22

endothelin is a

Answer 22

potent vasoconstrictor, produced by vascular endothelium

Question 23

endothelin converting enzyme (ECE)

Answer 23

rate limiting step

Question 24

endothelin is stimulated by

Answer 24

angiotensin, ADH, thrombin

Question 25

endothelin is inhibited by

Answer 25

NO and ANP

Question 26

endothelin is released form

Answer 26

vascular endothelium binds to ET receptors on VSMC (GPCRs coupled to Gq).

Question 27

endothelin negative feedback

Answer 27

via ET receptors on endothelial cells = NO production.

Question 28

Endothelin response

Answer 28

similar to α adrenergic response (vasoconstriction via IP3 and increased Ca2+) but different time course.

Question 29

endothelin is a natural counterpart to

Answer 29

NO