Lecture 9: Controlling regional blood flow

Question 1

What affect does vessel radius have on resistance and blood flow?

Answer 1

change in radius has a direct effect on resistance and therefore blood flow
larger radius = more blood can move through vessel = smaller resistance

smaller radius = less blood can move through vessel = larger resistance

Question 2

What mechanisms control vascular resistance ?

Answer 2

- Mechanical
= from within the vessel
= from outside the vessel
- Neural = sympathetic nerves
- Humoral = releases of hormones from organs

Question 3

What is vascular tone ?

Answer 3

controlling of blood through the contraction of the smooth muscle cells in the wall of the arterioles

Question 4

What is vasodilation?

Answer 4

widening of the vessel, increasing luminal radius = low resistance

Question 5

What is vasoconstriction?

Answer 5

narrowing of the vessel, decreasing luminal radius = high resistance

Question 6

What are arterioles ?

How do arteriole control region blood flow?

Answer 6

= resistance vessels that control regional blood flow and the distribution of flow within an organ

• blood flow to a region is controlled by adjusting arteriole(vascular) tone and radius
• each smooth muscle forming the wall of the arteriole makes a complete loop around the vessel . When they contract, the vessel constricts.

Question 7

What is cardiac output?

Answer 7

the dividing up of blood among different regions

Question 8

During exercise how is cardiac output distributed?

• CO increases where?
• CO decreases where?

Answer 8

• Increased blood flow to: muscle, heart and skin * except for maximal exercise
  - increased flow = decreased resistance
• Decreased blood flow to: GI tract and kidneys
  - decreased flow = increased resistance
• Constant blood flow to brain
• divergent flow depends on metabolic needs

Question 9

How is cardiac output distributed?

Answer 9

• arterial blood divid as it flow further from the heart
• —> continual branching of arterial network
• —> divides blood flow among the regional/organ circulations