Regulation of blood pressure Flashcards
What is blood vessel capacitance?
blood volume held at a given pressure (related to distensibility)
What type of muscle is present in arterioles?
active vascular smooth muscle (VSM)
What 3 reasons change the resistance to blood flow?
- sympathetic nerves - decreased diameter of arteriole/increased resistance to blood flow
- circulating catecholamines (e.g. adrenaline)
- other vascular substances
What are capillaries?
site of exchange - but not all perfumed with blood
What controls capillaries?
dilation/ constriction of arterioles (pre-capillary sphincters in mesentery & brain)
What regulates capillaries?
sympathetic innervation of vascular smooth muscle & vasoactive metabolites produced in the tissue
Describe how much elastin is found in veins vs arteries?
more elastic tissue in arteries
What blood vessel contains the largest % of blood in the cardiovascular system?
veins
What can increase the activity of veins?
alpha-adrenergic receptors
What is the equation for the velocity of blood?
v = Q/A
velocity = flow/cross-sectional area
What is blood flow determined by?
- pressure difference between vessel inlet & outlet
- resistance of vessel to blood flow
What is the blood flow equation?
Q = change P/R
flow = difference in pressure/resistance
What is the TPR (total peripheral resistance)?
resistance of entire systemic vasculature
Who’s law can be used to figure out the resistance to blood flow?
Poiseullie’s law
What is Poiseuille’s law?
R = 8nl/pieR^4
resistance = 8 x viscosity of blood x length of blood vessel/ pie x radius of blood vessel (^4)
describe the relationship between resistance to flow & vessel length & blood viscosity
RESISTANCE TO FLOW DIRECTLY proportional to vessel length and blood viscosity
describe the relationship between resistance to blood flow & the radius
resistance to flow is INVERSELY PROPORTIONAL to 4th power of the radius
Where is series resistance seen in blood vessels?
series resistance can be seen within an organ
What is the total resistance?
sum of individual resistances
What is the benefit of parallel resistance?
no loss of pressure
Why does pressure decrease with blood flow?
energy lost overcoming frictional resistance
What level of compliance (elasticity) does the aorta have?
low
What level of cardiac output is in the arteries?
remain high