Lecture 9 Flashcards
Why is it important that the arteries have high pressure?
High pressure allows for much larger control of flow.
How is blood distributed to organs? What are the rough relative proportions?
Cardiac output is distributed to all organs via blood vessels which run in parallel.
The distribution is overall adding to roughly 5L/min, in order of amount given at rest from highest to lowest is skeletal muscle (30%), gastrointestinal tract (25%), kidneys (20%), the brain (14%), the skin (7.5%) and coronary circulation (4.5%).
How does blood distribution change with exercise? Whats weird about maximum exercise?
Brain remains the same no matter what (roughly 750), heart muscle and skin increase with exercise. The kidneys, gastrointestinal tract and other organs recieve less with more exercise.
at maximum exercise the skin recieves far less blood flow because the body only wants to survive, it will deal with heat dispersion later.
How is the mean arterial pressure maintained during exercise?
Cardiac output increases, hence total peripheral resistance went down.
How is increased and decreased blood flow to different organs done?
Resistance is decreased in organs which need more blood (muscle, heart and skin) and is increased in organs which need less (kidneys, intestines, spleen, etc.
How is control of organ resistance and regional flow done? What is the associated equation?
The resistance vessels, arterioles, smooth muscle can relax to increase the size or can contract to decrease the size. The equation is R = 1 / r^4, this means a decrease in diameter has a huge effect on resistance.
What factors control the vascular resistance?
Locally mechanical responses to force from within the vessel (blood pressure) and from outside the vessel (e.g swelling)
Centrally via neurons and hormones released from remote organs like adrenaline.
