AP TEST 2 Part 2
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what are the two components of cardiac output?
heart rate and stroke volume
what are the three factors that determine stroke volume?
what control does the medulla exert over the heart?
- it sends signals through the parasympathetic system to slow the heart rate
- it sends signals through the sympathetic system to increase rate and increase contractility
why does it (medulla) do this?
it receives signals from baroreceptors and chemoreceptors in the large arteries and in the brain itself
describe the capillary bed
- 1) has a shunt to by-pass the bed when necessary
- 2) has pre-capillary sphincters that open the bed in response to local chemicals rather than nerves
- 3) pressure differences determine exit and entry to the capillary
what are the pressure differences at either end of the capillary bed?
- At arterial end: hydrostatic pressure higher than osmotic pressure
- At venous end: osmotic pressure higher than hydrostatic pressure
what are sinusoids?
open spaces where blood comes in direct contact with cells
what is a portal system?
where are they found?
- two distinct capillary beds joined by a vein
- found in liver and hypothalamus
what three things aid venous return to the heart?
- 1) one way valves
- 2) squeezing of veins by calf muscles
- 3) negative pressure in the chest during inhalation
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