Regulation Of Regional Vascular Beds

Question 1

Coronary vascular bed

Answer 1

Function: nourishment

Important anatomy: phasic flow

Myogenic tone: YES

Dominant regulatory mech: metabolic

Question 2

Cutaneous/skin vascular bed

Answer 2

Function: temperature

Anatomy: A/V shunts

Myogenic tone: NO

Dominant reg mech: sympathetic

Question 3

Skeletal vascular bed

Answer 3

Function: nourishment

Anatomy: capillary density is greater in slow twitch vs. fast

Myogenic tone: YES

Dominant reg: sympathetic (rest) and metabolic (active)

Question 4

Cerebral vascular bed

Answer 4

Function: nourishment

Anatomy: rigid cranium

Myogenic tone: YES +

Dominant reg : metabolic

Question 5

Intestinal vascular bed

Answer 5

Function: nutrient absorption

Anatomy: countercurrent exchange

Myogenic tone: NO

Dominant reg: metabolic

Question 6

Hepatic vascular bed

Answer 6

Function: metabolism +

Anatomy: sinusoids

Myogenic tone: ?

Dominant reg: metabolic

Question 7

Factors that regulate coronary blood flow to balance myocardial O2 supply and demain

Answer 7

During systole = reduction in blood flow due to the heart muscle contracting which physically compress the coronary arteries

During diastole = increased blood flow
—> LCA has more than RCA

Metabolic regulation:

Drop in O2 —> O2 demand goes up —> drives production of adenosine, H+, CO2, and K+

Net effect = vasodilation

Question 8

Mechanism of vasodilation

Answer 8

1. Low O2
2. Adenosine receptors stimulated
3. Stimulate K+ channels
4. Hyperpolarization of cells
5. Ca2+ influx channels are turned off
6. Decrease in intracellular Ca
7. Reduced contractility
8. Vasodilation

Question 9

Vasodilation mechanism involving CO2

Answer 9

Low O2 —> promote CO2 and H+ to leave the cardiomyocyte —> act in SmM —> vasodilation

Question 10

Sympathetic regulation of vasculature (coronary vascular bed)

Answer 10

Alpha-receptors = constrictors

Beta = dilators

Question 11

Effects of hypertension, partial coronary artery occlusion and severe aortic stenosis on coronary blood flow, O2 supply, and demand

Answer 11

Blood flow in arteries is decreased by atherosclerosis…thus blood is shunted to less resistant vessels…

This can cause ischemia downstream of the block, and thus ischemic coronary diseaes

Question 12

Roles of temperature, anatomy, and neural and local factors on regulation of cutaneous blood flow

Answer 12

Adapted for heat exchange

Anastomoses that shunt blood directly from arterioles to venules, bypassing capillaries…the proximity of major veins and arteries to this vascular bed allows for rapid heat exchange

If hot outside —> vessels dilate to increase surface area for cooling body off

Major regulation: sympathetic

Tone is increase drastically with sympathetic regulation…can go completely shut

NO parasympathetic innervation in skin

Metabolic and myogenic regulation is low in skin…good because want varying levels of blood flow to the skin

Locally, arterioles exhibit low autoregulation and instead vasoconstrict/vasodilate based on outside environment temperature

Question 13

Roles of neural and local factors and myogenic mechanisms in the regulation of skeletal muscle blood flow

Answer 13

Regulation:

REST = sympathetic regulation, keeps blood flow low

ACTIVE = metabolic regulation is dominant, as you need constant exchange of gases and metabolites to meet energy demands

Thus body makes sure to shunt blood to muscles that need it and not so much to muscles that don’t

Question 14

Roles of neural and local factors , such as increased arterial CO2 tension (PaCO2) and autoregulation in the control of cerebral blood flow

Answer 14

Metabolic regulation

Highly sensitive to CO2…when there is ischemia
—> CO2, K+, and adenosine levels promote vasodilation

Then steady-state regulation by myogenic response keeps the blood flow constant

Role of sympathetics and para…low

Myogenic response plays a very important role, because we always need constant supply of blood to the brain

Autoregulation range: 50-150 mmHg

• below = impaired dilation and artery collapse, ischemia
• above = forced mediated dilation, increased flow, vasogenic edema

Question 15

Roles of anatomy of the vascular tree and of neural and local factors in the regulation of intestinal blood flow

Answer 15

Center of villi = arterial flow coming in

Periphery of the villi = venous flow is leaving out

Exchange of O2 (important)

• during high flow in intestinal lumen, blood moving in is super oxygenated (O2 perfusion is high)
• during low flow —> more diffusiong of O2 through villi = optimal for nutrient/solute absorption in villi

Metabolic regulation = most dominant

Sympathetic role does exist = preferentially dilate areas of gut that are absorbing and constrict areas (via alpha-1 adrenergic) that are not active

Question 16

Functional hyperemia

Answer 16

Intestines shunt blood to places of more nutrient content for absorption

Activated by nutrients like oleic acid, glucose, FAs, electrolytes, and more

Hormones can affect this rate as well

Question 17

Roles of vascular anatomy and neural and local factors in the regulation of hepatic blood flow

Answer 17

Anatomy = liver has systemic circulation along with the portal venous system

Function = promote metabolism of circulating factors and to act as a blood reservoir

Both hepatic artery and portal vein blood enter a common sinusoid…where gaseous and metabolite exchange occurs —> dO2 blood goes to central veins —> normal venous return system

Metabolic regulation = dominant

Hepatic artery (high p) and portal vein (low p)

High resistance in artery reduces flow into sinusoid…so that it doesnt snuff out the portal venous blod

Metabolites affect this area the most

Sympathetic = can deplet liver reservoir by 50%