Vascular Signaling Pathways

Question 1

What are some vasoactive metabolites that lead to dilation?

Answer 1

Decreased pO2, increased CO2, decreased pH, increased K+, increased CO2

Question 2

Nitric oxide is produced by __________.

Answer 2

endothelial cells

Question 3

Nitric oxide synthase can be inhibited by _________.

Answer 3

cigarette smoke

Question 4

Explain the mechanism of nitric oxide.

Answer 4

Acetylcholine binds to GPCRs on endothelial cells, which activate Gq; Gq then produces IP3 through PLC which stimulates intracellular Ca2+ release; Ca2+ activates calmodulin which activates NO synthase; NO synthase breaks down arginine to citrulline and NO; NO passes into smooth muscle cells and activates guanylate cyclase; cGMP activates protein kinase G, which decreases intracellular [Ca2+] and thus inhibits smooth muscle contraction

Question 5

Describe the endothelin pathway.

Answer 5

Produced by endothelium, endothelin is a 21-amino-acid-long peptide that binds to GPCRs on smooth muscle cells that induce contraction; similar to alpha adrenergic receptors, in that it induces IP3 and calmodulin

Question 6

What is renin and how is it released?

Answer 6

It is a proteolytic enzyme that cleaves angiotensinogen to angiotensin I; it is produced by the kidneys and is released in response to decreased blood pressure, decreased sodium reabsorption, or sympathetic stimulation

Question 7

Angiotensin II binds to _________ and induces ___________.

Answer 7

GPCRs (specifically Gqs); systemic vasoconstriction, thirst, fluid retention, and aldosterone production via adrenal stimulation

Question 8

ADH is released by the ______ in response to _______; it induces ________.

Answer 8

hypothalamus and pituitary; hypovolemia, hypotension, and angiotensin II; increased water reabsorption in the kidneys

Question 9

Define natriuretic.

Answer 9

Something that induces sodium excretion

Question 10

ANP (____________) is a _________.

Answer 10

atrial natriuretic peptide; vasodilator in the vasculature and inhibitor of aldosterone release in the adrenal glands

Question 11

What is the myogenic response?

Answer 11

Smooth muscles in the blood vessels gradually constrict, leading to decreased flow; alternately, in vessels with low flow, smooth muscles dilate to increase flow. The overall effect is to minimize sudden changes in flow. This effect is independent of nervous input.

Question 12

Baroreceptors work by relying on ___________.

Answer 12

mechanosensitive sodium channels

Question 13

Baroreceptor neurons send axons to __________.

Answer 13

the cardiac-control center of the brainstem

Question 14

An increase in baroreceptor firing (which results from increased pressure) causes the brainstem to ___________.

Answer 14

increase parasympathetic stimulation to the sinoatrial node and vascular smooth muscles, which causes decreased chronotropy and vasodilation

Question 15

The primary mechanism by which tissues regulate their metabolic needs is through ________.

Answer 15

vasoactive metabolites, which can produce a 50-fold difference in blood flow

Question 16

Why does a high extracellular potassium level induce arteriole dilation?

Answer 16

Because the sodium-potassium pump cannot keep up with the activity of muscles, so potassium accumulates in the extracellular environment near active tissues

Question 17

Smooth muscle does not have __________.

Answer 17

sarcomeres, troponin, or tropomyosin

Question 18

Aortic baroreceptors head back to the medulla via the ________, while carotid sinus receptors proceed via the ________.

Answer 18

vagus nerve; glossopharyngeal nerve