lecture 21 Flashcards
arteries
- are stretchy and elastic
- they stretch to accommodate a large volume of blood and they need to recoil to push blood farther away from heart and maintain pressure
- they branch into arterioles
arterioles
- they are sympathetically innervated
- increase or decrease sympathetic input to regulate tone
- regulates blood pressure
venous system
- serves as a volume reservoir
- has low pressure
capillaries
- one cell layer thick
- exchange between blood and cells occur here
give an example of blood distribution on organ needs when under sympathetic control
- when in a sympathetic scenario we need more blood for skeletal muscle and we don’t need a larger proportion going to the GI tract because sympathetic control halts digestion
vasodilation
- increase diameter, so decrease in resistance
- decrease in blood pressure
vasoconstriction
- decrease in diameter, so increase in resistance
- increase in blood pressure
velocity of blood flow depends on
- diameter of blood vessel and how many there are
as blood flows through circulation
- it looses pressure and establishes a pressure gradient
why is pressure lost
- due to friction
- blood encounters friction by the nature of its viscosity
- friction between blood and vessel walls
Fluid flow refers to
cardiac output
the laws of fluid flow are
flow is proportional to the pressure gradient and inversely proportional to resistance
greater resistance means faster or slower flow
- slower flow
- we will vasoconstrict
smaller resistance means faster or slower flow
- fast flow
- meaning we will vasodilate
venous return
the flow of blood into the right atrium from the peripheral vessels
blood flow velocity is slowest through _________
capillaries
capillaries have the smallest individual diameters, but have ….
largest cross sectional area because we consider collectively as a whole
does the aorta have a large or small cross sectional area
small because there is only one aorta
metarterioles
- provide an alternative route if precapillary sphincters are closed
- they also allow for larger materials (WBC) to bypass narrow capillaries and reach venous circulation
precapillary sphincters
- open and close in respond to local metabolic conditions
- smooth muscle that can relax or contract and pinch off blood flow to a capillary
capillaries are the site of _______
exchange
capillaries are _____
- leaky
- approx 3L/day of fluid is filtered out of capillaries
what happens when stuff leaks out of your capillaries into interstitial fluid
your lymphatic system will collect it, sweep it, scan it and makes sure there’s nothing that shouldn’t be there and then it will drop it back into your cardiovascular system
