Circulation & Hemodynamics Flashcards
What is the relationship b/w the amt of blood in the arteries and their combined cross-sectional area?
small cross-sectional area
lots of blood
What is the relationship b/w the amt of blood in the veins and their combined cross-sectional area?
large cross-sectional area
lots of blood
What is the relationship b/w the amt of blood in the capillaries and their combined cross-sectional area?
large cross-sectional area
small amt. of blood
When an artery is constricted, which changes: resistance or volume?
resistance; volume doesn’t change much
When a vein is constricted, which changes: resistance or volume?
volume; blood is pushed back into the arterial side
-resistance isn’t changed much
What is the physiological benefit of having a huge cross-sectional area in the capillary beds relative to the amount of blood in the capillary system?
- sluggish velocity
- diffusion over a longer period of time
Define laminar flow.
-blood flowing in an even pattern
Define turbulent flow.
-chaotic, churning flow
What is the equation for Reynold’s number?
(density x diameter x velocity) divided by viscosity
What will an increase in blood density do to Reynold’s number and bloodflow?
- increase Reynold’s number
- shift toward turbulent flow
What will an increase in diameter of blood vessel do to Reynold’s number and bloodflow?
- increase Reynold’s number
- shift toward turbulent flow
What will an increase in velocity do to Reynold’s number and bloodflow?
- increase Reynold’s number
- shift toward turbulent flow
What will an increase in viscosity do to Reynold’s number and bloodflow?
- decrease Reynold’s number
- shift toward laminar flow
What is the approx. cutoff of Reynold’s number to be considered laminar flow vs. turbulent flow?
> 2000 = turbulent
How does velocity relate to bruits?
-increased velocity = increase in bruits
How does viscosity related to bruits?
-decrease in viscosity = increase in bruits
What happens to blood flow as resistance increases?
blood flow decreases
What happens to blood flow as the difference in pressure increases?
blood flow increases
What is Poiseuille’s equation to determine resistance?
(8 x viscosity x length) divided by (pi x radius to the 4th)
What causes the biggest change in the resistance of a blood vessel?
diameter … because length won’t change … and viscosity likely won’t change either
What happens to the total resistance of resistances in a series?
increase
What happens to the total resistance of resistances in parallel?
decrease
Define arterial systolic pressure.
- the clinically reported “systolic pressure”
- the greatest pressure reached in a large artery
Define diastolic pressure.
-the lowest pressure reached in a large artery
What’s the equation for blood pressure.
BP = SV x HR x TPR
How does stroke volume affect blood pressure?
as stroke volume gets larger, BP increases
How does heart rate affect blood pressure?
as heart rate increases, BP increases
How does total peripheral resistance affect blood pressure?
as TPR increases, BP increases
How does compliance affect blood pressure?
as compliance increases, BP decreases
What is pulse pressure?
systolic pressure minus diastolic pressure
How does compliance affect pulse pressure?
as compliance decreases, pulse pressure increases
What is the equation for MAP?
diastolic pressure x 1/3 pulse pressure
Is the MAP closer to systolic pressure or diastolic pressure, and why?
diastolic pressure, bc the body spends more time in diastole
What happens to blood vessels during a sympathetic response?
arterioles constrict, causing total peripheral resistance to increase
veins constrict, causing capacitance to decrease
What happens to blood vessels during a parasympathetic response?
arterioles dilate, causing total peripheral resistance to decrease
veins dilate, causing capacitance to increase
Define compliance.
relationship bw the amount of blood a vessel can hold at a given pressure
ex: vessels w/ high compliance can hold more blood at a certain pressure than a vessel w/ low compliance
Do veins have a high compliance or a low compliance?
high
Do arteries have a high compliance or a low compliance?
low
Pathology: how does arteriosclerosis affect compliance?
-plaque deposits make arteries less compliant
Pathology: how does aging affect compliance?
artery walls become stiffer with age
Pathology: how does hypertension affect compliance?
once HTN has become “established”, the artery walls have decreased compliance and don’t recoil
