Phys Cuteneous circulation

Question 1

Thermoregulation and the skin

Answer 1

when hot, skin acts as a good radiator and when cold skin acts as a good insulator

Question 2

importance of the venous plexus in thermoregulation

Answer 2

when we are really hot the venous plexus accumulates a large amount of blood to bring more blood to the surface to disapate heat

Question 3

what area contains most of the cutaneous blood volume

Answer 3

venous plexus (high capacitance)

Question 4

Arteriovenous anastamoses (cutaneous circulation)

Answer 4

allows a considerable amount of blood flow to enter the superficial venous plexus (bypassing the superficial capillary beds) and allows us to disapate heat

Question 5

Anteriovenous anastamoses and cooling

Answer 5

cooling increases SNS activity and closes the AVA shunt to preserve body heat

Question 6

Anteriovenous anastamoses and warming

Answer 6

warming decreases sympathetic tone resulting in passive vasoconstriction and venodilation to dissipate heat

Question 7

Deep vs Superficial cutaneous circulation

Answer 7

Superficial cutaneous circulation provide little insulation and radiate heat well (when we are hot) Deep cutaneous circulation parallels the arterial system and are more insulated (when we are cold)

Question 8

how is core body heat preserved

Answer 8

Counter current heat exchange

Question 9

Counter Current Heat Exchange

Answer 9

The close association between arteries and veins permits direct transfer of heat to help preserve body heat

Question 10

Warm environment thermogram

Answer 10

small temperature gradient between core and sufrace

Question 11

Cold environment thermogram

Answer 11

Large temperature gradient between core and surface due to cutaneous vasoconstriction and counter current exchange (try to maintain core heat)

Question 12

Control of skin blood flow under resting conditions, whole body heating, and cooling

Answer 12

1.) Resting: 200-500 ml/min (5-10% CO) 2.) Whole Body Heating: up to 40 fold increase in blood flow (8L/min) 3.) Cooling: decrease cutaneous flow to negligible levels

Question 13

Response to 5C increase in body temp

Answer 13

causes cardiac output to increase markedly to support the increased skin blood flow needed to enhance dissipation of heat. Flow must decrease to other areas (splanchnic organs, kidneys, skeletal muscle) MAP still falls (can get too low causing us to pass out)

Question 14

Neural Control of Skin Blood Flow

Answer 14

Sympathetic tone (tonic a1 receptro mediated) Note: NO PARASYMPATHETIC INNERVATION (NO B RECEPTORS)

Question 15

Passive vasodilation

Answer 15

caused by a decrease in sympathetic tone

Question 16

Acral regions

Answer 16

Hands, feet, nose, ears - Hight sympathetic tone- increases blood flow due to passive vasodilation

Question 17

Non-actral regions

Answer 17

body, arms, legs - LOW sympathetic tone (only a small amount of passive dilation) PRESENCE OF ACTIVE VASODILATOR SYSTE IN NONACRAL REGIONS OF SKIN

Question 18

Sympathetic Vasodilation

Answer 18

Neurally mediated cutaneous vasodilation that is coupled to the activation of sweat glands. Results in the release of unidentified cotransmitter from cholinergic nerves resulting is a second rise in flow to nonacral regions

Question 19

Indirect heating

Answer 19

Increased blood temperature causes a relfex increase in cutaneous blood flow (decreased sympathetic activity - vasodilation to move more heat to the periphery to dissipate) . Thermal sensors in the skin, hypothalamus, and spinal cord are very sensitive to changes in core blood temperature.

Question 20

Cutaneous Veins

Answer 20

Highly complinat- relax when heating (facilitates more blood to increase heat loss)

Question 21

Metabolic control of cutaneous blood flow

Answer 21

POOR