Blood Flow & Response to Exercise

Question 1

Factors that affect Velocity of Blood flow (4)

Answer 1

1. Diameter - increased diameter = decreased velocity (INVERSLY related); decreased diameter = increased speed (HTN, athersclerosis)
2. Length - an increase in length will decrease flow (length doubles, flow decreases 50%)
3. Viscosity - as blood thickens, flow decreases
4. Radius - if tube radius increases, velocity increases (radius doubles, flow increases 16 fold)

Question 2

Sheer Stress

• what is it
• effects of exercise
• compesations

Answer 2

friction on endothelial wall as blood flows through the vessel; based on blood viscosity & rate of sliding

Sheer stress INC w/ exercise, due to increased blood volume

Compensates by releasing nitric oxide (which is a vasodilator)

Question 3

Hyperemia

- active vs. reactive

Answer 3

Active - proportional increase in blood flow due to increase in metabolic demands
- aka functional hyperemia

Reactive - blood flow is transiently increased to do period of ischemia/total occlusion

• degree & duration of increased blood flow is proportional to the time of ischemia
• EXCESS blood flow

Question 4

Blood flow & Response to Exercise

Answer 4

Blood flow INCREASES due to..

• increased capillarization (higher capillary to fiber ratio)
• greater opening of existing capillaries
• more effective blood redistrubtion
• increased blood volume

Question 5

BP & Response to Exercise

Answer 5

intra-arterial pressure during systole & diastole

BP = Q x total peripheral resistance

Response to exercise:

• systolic BP increases linearly to exercise intensity
• diastolic BP slightly decreases or remains the same
• slight increase in mean arterial pressure (MAP)
• decrease in total peripheral resistance (TPR) due to vasodilation

Question 6

Control of BP

Answer 6

long term adaptations & control by KIDNEYS - by nervous system

short term adaptations - CV system

Question 7

Mean Arterial Pressure

Answer 7

cardiac output x total peripheral resistance (Q x TPR)
aka the AVERAGE blood pressure

system that can monitor the pressure, assess the correctness of pressure, & adjust the pressure to the required level
- by altering cardiac output

Reflex arc used in day to day BP control

slight increase w/ exercise

Question 8

Total Peripheral Resistance

Answer 8

total resistance of blood flow in the systemic circulation

decreases w/ exercise due to vasodilation of the exercising muscles

Question 9

Venoconstriction

Answer 9

does not significantly reduce radius of veins –> little change in resistance compared to arterioles

does DEC venous compliance (flexibility) which…

• increases pressure
• increases venous return to heart