Mid: Thermoregulation Additional Slides Flashcards
what percent of blood flow is going skeletal muscle at rest? and what percent during maximal exercise?
- 15-20% of cardiac output
- 80-85% of cardiac output
redistribution of blood during exercise depends on what?
Intensity
oxygen delivery changes during exercise due to? (2)
- an increased cardiac output
2. a redistribution of blood flow (use of autoregulation)
Cardiac out put increases as a linear function with VO2…. what maintains this linear relationship?
idk lets look it up right now
during exercise what happens to blood flow to visceral organs and inactive tissues?
what happens at active skeletal muscle?
- vasoconstriction
- vasodilation
what causes vasodilation during exercise: (autoregulation) (70
- increased temp
- elevated CO2
- Lowered pH
- Adenosine
- Nitric oxide
- ions (mg2 and K+)
- Ach
what cause vasoconstriction during exercise?
norepinephrine
epinephrine
capillary recruitment increases from 5-10% to what percent during exercise?
almost full
what do norepi and epi do during exercise?
increase calcium available to myocardial cell= increased cross bridge activation and increased force production
Pre capillary sphincters can be relaxed to increase local blood flow. what factors control this relaxation?
idk lets look!
greater capillary perfusion at the lungs =
increases/decreased local blood flow?
increase/decrease speed of blood flow?
hate her
1 of every ? capillaries in muscle is open at rest
30-40
capillary perfusion during exercise does what? (3)
- increases blood flow to muscle
- reduces speed of blood flow
- increases surface area for gas exchange at working tissues
what does nitric oxide do to promote vasodilation
- promotes smooth muscle relaxation which results in vasodilation and increased blood flow
where is nitric oxide produced?
endothelium of the arterioles
what is the 4 components of the recipe for success to ensure adequate blood flow to muscles
- provide adequate cardiac output
- distribute arterial blood tot he muscles demanding oxygen
- divert some of the blood flow away from less active areas
- maintain blood pressure
what does flow equal?
and what does blood pressure maintained by?
Flow= change in pressure/resistance
maintain Pressure=increase flow and decrease resistance
does systolic or diastolic of both BP increase during exercise?
just systolic, diastolic remains relatively constant
why does MAP not increase as much as cardiac output during exercise?
in order for the heart to eject blood, the pressure generated by the left ventricle must exceed the pressure in the aorta (MAP)
- an increase in aortic pressure = a decrease in stroke volume
- -> minimized during exercise by arteriole dilation
what one variable decreases during exercise
total peripheral resistance
why is mean arterial pressure higher in arms compared to legs only in exercise?
(we supposed to think about ALL the variables influences HR and MAP)
greater sympathetic outflow to the heart during arm exercises compared to legs which results in increase in BP
- there is vasoconstriction in all the inactive muscle groups
- -> in larger muscle groups (legs) the more resistance arterioles that are dialated (lower peripheral resistance = lower pressure)
cardiac output=
HR x SV
fick equation: VO2 =
Q x a-vO2 diff
VO2 max =
max Q x max a-vO2
