Muscle Blood Flow and CO during exercise Flashcards
What is the average BF to skeletal muscle at rest?
3-4 ml/min/100g muscle
How much with BF during exercise?
50-80 ml/min/100g muscle
Describe the flow during muscle contraction of blood and why it happens
Flow increases or decreases with each contraction due to compression of blood vessels by the muscles
-flow increases between contractions
- decreases during a contraction
What happens to capillaries during exercise?
They open
What causes vasodilation of the muscle arterioles?
local chemical effects
Why is blood flow locally increased to the muscle?
- O2 is reduced because of increased muscle
- increases vasodilation substances
List vasolidation substances
Adenosine, K ions, ATP, lactic acid, CO2
Sympathetic fibers are vasoconstrictor or vasodilation?
Vasoconstrictor mostly
Sympathetic stimulation increase secretion of what neurotransmitters?
NE and Epinephrine
NE causes vasoconstriction via which receptors?
Alpha
Epinephrine causes vasodilation via which receptors?
Beta
List the 3 major circulatory adjustments that happen during exercise
- mass sympathetic nervous system discharge
- Increase in AP
- increase in CO
Why is an increase in CO essential during exercise?
to supply O2 and nutrients in an increases metabolic need
What is VR depends on the increase of?
psf during exercise
how does coronary venous blood from the LV return to the heart?
Via coronary sinus
how does coronary venous blood from the RV return to the heart?
anterior cardiac veins
What happens to capillary blood flow during systole?
falls because of compression of the LV
If the strength of contraction increases, then the rate of the coronary blood flow does what?
Increases too
What is the major factor in local coronary blood flow regulation?
Oxygen demand
What substance is released in response to a decrease in O2 concentration in the heart to cause vasodilation?
Adenosine
How does O2 deficiency affect arterial wall contraction?
As O2 is needed, vessels cannot continuously contract and thus vasodilate
Which receptors are constrictors of coronary vessels?
alpha
The NT Acetylcholine acts via which division of the nervous system to affect coronary vessels directly?
Parasympathetic
T/F the stimulation of autonomic nerves can indirectly or directly influence coronary blood flow
True
What is used in place of carbohydrates by the cardiac muscle?
Fatty acids
What is the mechanism for energy in anaerobic conditions for cardiac metabolism?
Anaerobic Glycolysis
What is the precursor to adenosine that is degraded in ischemia?
ATP
What is one of the major causes of cardiac cellular death during myocardial ischemia?
prolonged coronary ischemia (>30min)
