Regulation of Regional Circulations (Middlekauff)

Question 1

Function of skeletal muscle circulation

Answer 1

1) BP maintenance
2) O2/substrate delivery and waste removal from exercising muscle

Question 2

What happens to skeletal muscle circulation when you hemorrhage?

Answer 2

Vasoconstrict blood vessels in skeletal muscle (decrease flow 5 fold) to perfuse organs instead

Question 3

How does working muscle get increased blood flow despite sympathetic stimulation that would tend to vasoconstrict?

Answer 3

1) Metabolic vasodilation: ischemic metabolites cause local blood vessels to dilate; also capillary recruitment shortens distance blood has to go to get to muscle
2) Mechanical skeletal muscle pump: muscle contracion during exercise (or just walking) decreases venous pressure so blood wants to flow to that muscle better

Question 4

Three processes of heat loss

Answer 4

1) Radiation (difference between skin and air)
2) Conduction-convection (use air currents)
3) Evaporation of sweat

Question 5

Arteriovenous anastomoses (AVAs)

Answer 5

Direct connection between arteriole and venule in acral skin (hands, feet, lips, nose, ears)

Normally constricted by sympathetic, but when temperature rises ans sympathetic stim stops, AVAs dilate and bring more blood to skin for heat loss

Question 6

Cold paralysis (or paradoxical cold vasodilatation)

Answer 6

When it’s cold, neurotransmission is slow so even though you want to release NE to alpha1 receptors to vasoconstrict, it takes a while so you get increased blood flow to the skin.

Then skin is warmed and neurotransmission faster, and get vasoconstriction finally–but cycles again

Question 7

Heating and cooling normal effects on skin circulation

Answer 7

Hot: increase skin blood flow (vasodilate to AVAs)

Cold: decrease skin blood flow (vasoconstrict to AVAs)

Question 8

Spinal reflex

Answer 8

If you put right hand into ice, skin on left hand vasoconstricts

Question 9

Hypothalamus regulation of temperature

Answer 9

Temperature sensors in anterior hypothalamus –> sympathetic nerve activity when cold –> vasoconstricts in the ACRAL skin

(vasodilation to non-acral skin but this isn’t important)

Question 10

What happens to skin circulation when you hemorrhage?

Answer 10

Vasoconstriction (look cold and pale), and venoconstriction to increase preload so not good to give warm blanket because that would cause vasodilation in skin and bring blood away from vital organs!

Question 11

Problems when you exercise on a hot day

Answer 11

1) Increased core temp so need more skin blood flow to cool
2) Decreased peripheral resistance due to vasodilation in exercising muscle
3) Plasma volume decreased due to transcapillary filtration (fluid loss from capillaries)

CAN GET HYPOTENSION AND COLLAPSE

Question 12

Heat stress

Answer 12

First sign of serious heat illness

Cramps and confusion

Question 13

Heat exhaustion

Answer 13

Excessive loss of fluids, relative volume depletion. Core temperature not elevated

Heavy sweating, paleness, cramps, fatigue, dizziness, nausea, heataches, rapid breathing and pulse

Question 14

Heat stroke

Answer 14

Untreated heat exhaustion

Core temperature now elevated, dry skin, loss of consciousness, seizures, rapid weak pulse, vomiting

Question 15

Are cerebral vessels in the brain sensitive to CO2?

Answer 15

Yes, sense arterial CO2

If high CO2 (hypercapnia), vasodilation gives headache or pass out

If low CO2 (hypocapnia) get vasoconstriction