Blood Vessels and Hemodynamics for Exam 3 Flashcards
what is blood flow?
the volume of blood that flows through a tissue in a given period of time (mL/min)
what does cardiac output represent?
total blood flow relative to the heart
how does cardiac output become distributed into circulatory routes that serve various tissues? (2)
- pressure differences
- resistance to blood flow
how does pressure relate to blood flow?
blood flows down a pressure gradient; the greater the pressure difference the greater the blood flow
how does resistance relate to blood flow?
the higher the resistance, the smaller the blood flow
what is blood pressure generated by?
the contraction of ventricles causing hydrostatic pressure to be exerted by blood on walls of vessels
what 3 things determine blood pressure?
- cardiac output
- blood volume
- vascular resistance
where is blood pressure highest?
at the aorta and large systemic arteries
in a resting young adult, give blood pressure during systole and diastole
about 110 mmHg in systole
about 70 mmHg in diastole
when does blood pressure fall naturally?
pressure falls progressively as distance from left ventricle increases
sum up blood flow due to pressure changes in 5 points
- flows down a pressure gradient
- due to the force of heart contraction
- highest at the heart (the driving pressure) and decreases over distance
- also related to compliance or distensibiltiy of vessels
- decreases 90% from aorta to vena cava
describe blood pressure in the venous system
much much lower, close to 0 when reenter the heart
what is blood flow directly propotional to? what is it iversely proportional to?
- blood flow is directly proportional to the difference in blood pressure between two points in the circulation (flows down a pressure gradient)
- blood flow is inversely proportional to resistance (more resistance less blood flow)
what is the rate of blood flow equal to?
the pressure difference divided by the resistance
is resistance or pressure chhane more important in regulating local blood pressure?
resistance is more important than pressure changes in influencing local blood pressure
what is mean arterial pressure (MAP)?
average blood pressure in arteries; approx 1/3 between diastolic and systolic pressures
how is MAP calculated?
MAP = diastolic BP + 1/3 (systolic BP-diastolic BP)
how can cardiac output be calculated when given MAP and R?
CO = MAP/R
describe what happens to blood pressure when a decrease in blood volume is greater than 10%
blood pressure drops
if blood volume increases, what will likely happen to blood pressure?
blood pressure will likely also increase
what is vascular resistance?
opposition to blood flow caused by friction between blood and walls of blood vessels
what does the friction between blood and walls of vessels depend on? (3)
- size of lumen
- blood viscosity
- total blood vessel length
describe how lumen size relates to resistance to blood flow
the smaller the lumen the greater the resistance to blood flow
how is resistance related to diameter of blood vessel lumen?
resistance is inversely proportional to the fourth power of the diameter (d) of blood vessels lumen