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82 Cards in this Set

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What is blood pressure?

hydrostatic (fluid) pressure




force of blood exerted against walls of vessels

what is blood flow?

volume of blood flowing through a structure per unit time (mL/min)

what is resistance?

opposition to blood flow through a vessel

Where does blood always flow?

from region of higher pressure to region of lower pressure




bulk flow is down pressure gradient

When does blood flow increase?

as pressure difference between two points increases and as resistance to flow decreases

Blood flow equation

The change of pressure in the blood flow equation is referring to what?

perfusion pressure

Largest to smallest mean diameter of blood vessels

vein>artery>capillary

Compliance =

change in volume/change in pressure

What kind of pressure are we referring to in the compliance equation?

transmural pressure

What happens to compliance with age?

decreases

What does systole generate for blood flow?

pressure gradient and it must be maintained during diastole

What acts as pressure reservoirs to drive blood into vessels throughout cardiac cycle?

large arteries have thick, elastic walls with lots of elastin




helps smooth flow of blood throughout circuit

Elastic recoil in arteries has two phases:

ventricular contraction and ventricular relaxation

3 steps in ventricular contraction

ventricle contracts, semilunar valve opens, aorta and arteries expand and store pressure in elastic walls

3 steps in ventricular relaxation?

isovolumic ventricular relaxation occurs, semilunar valve shuts, preventing flow back into ventricle, elastic recoil of arteries sends blood forward into rest of circulatory system

What are venules?

collect venous blood from capillary beds




decrease in smooth muscle, elastin or collagen

what are veins?

large vessels with all 3 layers of extensive sympathetic innervation




walls are thin and lumens are large




blood pressure is very low

What do the thin walls and large lumens in the veins act as?

volume reservoirs

what aids return of blood to heart against gravity?

venous valves in limbs

What is the skeletal muscle pump relfex initiated by?

stimulation of plantar surface of the feet

what do muscle contractions do to the veins?

squeeze veins in muscles and drives blood toward the heart




this augments venous return

what prevents retrograde blood flow?

venous valves

when do the veins refill?

during relaxation of skeletal muscle

what happens to skeletal muscle pump activity when walking or running?

the activity is intensified

What contributes to resistance?

viscosity of blood




total blood vessel length




blood vessel diameter

What type of relationship do resistance and viscosity have?

they are proportional

What type of relationship do resistance and vessel length have?

they are proportional due to friction

what is the most important fact in resistance to blood flow?

blood vessel diameter

Which vessel diameters change the most?

arterioles

what are diameters of arterioles constantly regulated to control?

blood flow to specific tissues




arterial blood pressure

If you decrease the radius of a vessel by 1/2 you increase the resistance by

16 fold

What is R often referred to as in CV physiology?

peripheral resistance, because R in heart is so low

vasoconstriction?


decrease in arteriole diameter

vasodilation?

increase in arteriole diameter

What is total peripheral resistance known as?

systemic vascular resistance

TPR =

(mean aortic pressure - mean vena caval pressure)/cardiac output

Mean aortic pressure at rest?

98 mmHg

Mean vena caval pressure at rest?

3 mmHg

mean cardiac output at rest?

2.5 L/min

what is the average TPR at rest?

38 mmHg/L/min

Why is vena caval pressure often ignored?

it is so low that it does not impact it

Mean aortic blood pressure (Pa) =

CO x TPR

Pulmonary vascular resistance =

(mean pulmonary artery pressure - mean pulmonary venous pressure)/CO

What effect would dehydration have on arterial pressure?

causes decreased CO because preload is decreased which reduces SV




TPR is increased because arterioles in the kidneys, splanchnic circulation and resting skeletal muscle are constricted to minimize the fall in arterial pressure and diverts blood to essential organs

What happens to blood pressure in exercise?

cardiac output increases which would increase blood pressure but...




TPR decreases in a compensatory manner

how does TPR decrease in a compensatory manner during exercise?

with a four fold increase in CO during exercise, skeletal muscle arterioles increase in diameter decreasing TPR by about 1/4th causing aortic pressure change to be negligible

What happens to renal and splanchnic arterioles during exercise?

decreases flow by about 20%

What is MAP?

blood pressure driving blood into tissues over entire cardiac cycle

estimate MAP by:




MAP =

diastolic pressure + (pulse pressure/3)



What is pulse pressure?




pulse pressure =

systolic P - diastolic P

What is peak pressure?

systolic pressure (SP)

what is the pressure just prior to ventricular ejection?

diastolic pressure

what is DP determined by?

arterial compliance and the residual arterial volume immediately prior to the next cardiac region

What is low pulse pressure called?

thready

what is high pulse pressure called?

bounding

What factor determine mean arterial pressure in the long term?

blood volume (renal physiology)

what factors determine short-term mean arterial pressure?

MAP = CO x TPR




Cardiac output = HR x SV




TPR is sum of R to blood flow of all vessels

How is MAP controlled?

use the autonomic NS to increase MAP



increased SV directly increases pulse pressure

decreased heart rate increases time for aorta to empty so lowers diastolic pressure increasing pulse pressure



increased SV and decreased heart rate together increase pulse pressure even more

Stiffening of arteries leadsto leads to higher systolicpressure (increased pressurerequired to distend) and lowerdiastolic pressure increasingpulse pressure



Increased vasoconstrictionincreases TPR which causesblood to back up and pusharteries to their elastic limitand stiffen them leading toincreased pulse pressure

Combined stiffening andincreased TPR has a dramaticeffect on pulse pressure

PDA leads to increased LVSV and increased aortic systolicpressure. Additionally, aorticdiastolic pressure is lowerbecause blood runs out of theaorta by two pathways sopulse pressure is dramaticallyincreased




Aortic regurgitation has asimilar effect in that bloodleaves via two pathways bothinto the systemic circuit andback into the left ventricle soSV is increased in systole dueto the backflow and increasespulse pressure

increase in SV leads to

greater increase in aortic volume

greater increase in aortic volume leads to

increase in pulse pressure

increase in pulse pressure leads to

increase in SP

decrease in SV leads to

smaller increase in aortic volume

smaller increase in aortic volume leads to

decreased pulse pressure

decreased pulse pressure leads to

decreased SP

increase in C leads to

decrease in pulse pressure

decrease in pulse pressure leads to

decrease in SP

decrease in C leads to

increase in pulse pressure

increase in pulse pressure leads to

increase in SP

increase in HR leads to

decreased time for run off

decreased tim for run-off leads to

greater arterial volume remaining at the end of diastole

greater arterial volume remaining at the end of diastole leads to

increase in DP

Decrease in TPR leads to

increased rate of run off

increased rate of run-off leads to

less arterial volume remaining at the end of diastole

less arterial volume remaining at the end of diastole leads to

decreased DP