Lecture 3 - Local Control of Circulation

Question 1

Tissues respond within seconds by releasing _______ metabolites when any intervention decreases their supply of _____.

Answer 1

Vasodilator metabolites

O2

Question 2

Lactic acid effectively causes vasodilation by acidifying the tissue environment. In response, vascular smooth muscle cells (VSMCs) decrease _____ entry, thus decreasing tone.

Answer 2

Ca++

Question 3

How does a small accumulation of extracellular K+ affect VSMC tone?

Answer 3

It causes vasodilation, likely by stimulating inward K+ channel rectifiers that hyperpolarize the cell and decrease Ca++ influx.

Question 4

Adenosine is a ________ (vasodilator or vasoconstrictor?) that acts by decreasing intracellular ____, increasing _____, and inhibiting __-type _____ channels (which prevents the release of NE from sympathetic neurons.)

Answer 4

Vasodilator

Ca++

cAMP
L-type Ca++ channels

Question 5

How is an increase in [CO2] in the brain similar to Lactic Acid with regard to their effects on VSMCs?

Answer 5

Increase [CO2] acidifies the microenvironment –> decreases intracellular Ca++ –> decrease tone.

Question 6

______ hyperemia describes how VSMCs respond to transient occlusion of a blood vessel. As the blood flow returns, it carries away the local _____ (vasodilator or vasoconstrictor?) metabolites. How is this different from Active Hyperemia?

Answer 6

Reactive Hyperemia

Vasodilator

Active Hyperemia describes how blood flow to tissue changes proportionately to changes in its metabolism (in other words, in response to changes in the tissue’s activity/O2 demand.)

Question 7

______ mechanisms are acute response mechanisms that cause blood vessels to _____ in response to increased pressure and _____ in response to decreased pressure.

Answer 7

Myogenic Mechanisms

Constrict

Dilate

Question 8

There are different types of NO-synthase enzymes. Which one is Ca++ INDEPENDENT?

Answer 8

iNOS is Ca++ independent. Its activity is stimulated by cytokines and bacterial endotoxins.

eNOS and nNOS are Ca++ DEPENDENT.

Question 9

NO acts directly as a vasodilator by increasing c____, but it also prevents _____ and leukocyte adhesion to vascular endothelium and it scavenges _____ anions (anti-inflammatory effect).

Answer 9

cGMP

Platelet

Superoxide anions

Question 10

_____ is a local acting vasoconstrictor that acts by stimulating the production of IP3 and thus, Ca++ influx (effectively increases the intracellular Ca++ concentration.)

Answer 10

Endothelin (ET1)

Question 11

______ is a local acting vasodilator produced by VSMCs. It acts by effectively increasing intracellular cAMP –> activates PKA –> phosphorylates (deactivates) MLCK –> less smooth muscle contraction.

Answer 11

Prostacyclin

Question 12

Cardiac muscle cells have ____ adgrenergic receptors that bind Epi and are the major contributors to increasing cardiac contractility. The also have ____ adgrenergic receptors that bind NE, but these are less effective.

Arteriolar constriction occurs through NE binding ___ and ___ receptors –> activates the IP3 pathway.

Conversely, Arteriolar dilation is facilitated by NE binding ____ receptors –> activates the cAMP/PKA pathway.

Venus constriction occurs through the same way arteriolar constriction occurs. How is that?

Answer 12

Beta 1

Alpha 1

Alpha 1 and Alpha 2

Beta 2

NE acting on alpha 1 and alpha 2.