Flashcards in Lecture 22 Cardiovascular system 3 vessels, flow & pressure Deck (23)
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1
Arteries
conducting vessels
high pressure
thick walls
elastic arteries
"pressure reservoirs"
muscular arteries
smooth muscle, endothelium, elastic tissue, fibrous tissue
2
Arterioles
resistance vessels
small diameter
smooth muscle in walls
vasoconstriction/vasodilation regulates blood flow to capillaries
endothelium, smooth muscle
pressure decreases steeply because of high resistance to blood flow (biggest P drop)
3
Capillaries
exchange vessels
microscopic
very thin walls
fluid filters out/in
permeability: continuous< fenestrated
4
Veins
low pressure conducting vessels
thin walls
high compliance ("volume reservoir")
valves ensure one-way flow back to heart
endothelium, smooth muscle, elastic tissue, fibrous tissue
Pressure lowest in venules and veins
5
Overall circuit is arranged in
series
pressure drops continuously from arteries to capillaries to veins
6
Blood supplies to different organs are arranged in
parallel
high pressure, oxygenated blood delivered to all organs
independent regulation of blood flow to different organs
7
Blood flow and blood pressure
Flow = deltaP/R
Cardiac output, blood pressure, resistance
8
Cardiac output
CO= total blood flow
CO= SV X HR
9
Blood pressure
difference (deltaP) between arteries and veins is the driving force for blood flow
MAP
P high in arteries
P low in veins and venules
P intermediate in Pulmonary arteries
biggest P drop in arterioles
10
Mean arterial pressure (MAP)
total deltaP of the systemic circuit
MAP = diastolic P + 1/3 (systolic P - diastolic P)
s=120 d=75 answer=90
11
Resistance
factors that oppose or reduce blood flow:
blood viscosity (high RBCs -> high viscosity)
length (L) of blood vessel - longer = more resistance
radius (r) of blood vessel: R a 1/r4
12
Vessel radius
diameter
is the major factor that determines resistance
small change in vessel radius results in large change in resistance and flow
if diameter is 2 times higher then resistance is down 16x and flow is increased 16x
13
Total Peripheral Resistance
TPR
is the resistance of ENTIRE systemic circuit
14
Vasodilation is _ while vasoconstriction is _
locally controlled
sympathetic alpha adrenergic
15
Arterial BP
MAP= CO x TPR (relationship of factors that determine BP)
normal MAP is about 90 mm Hg
16
Factors that affect arterial blood pressure
hear rate: increase HR -> increase CO -> increase BP
stroke volume: increase SV -> increase CO ->increase BP
blood volume: increase BV -> increase SV -> increase CO ->increase BP
vascular resistance: increase TPR -> increase BP
17
Blood volume is determined by
fluid intake vs fluid loss
18
Homeostatic control of blood pressure
Cardiovasular control center
arterial baroreceptors
19
Cardiovasular control center
located in the medulla oblongata
increases inputs from sensory receptors and higher brain centers
activates autonomic NS to regulate BP
20
Arterial baroreceptors
stretch receptors located in aorta and carotid arteries
low BP ->decreased stretch of artery walls -> frequency of APs -> increase in sympathetic NS activation
21
sympathetic nervous system effects
high HR (B1) -> increase CO
high contractility (B1) -> increase CO
increased vasoconstriction (a1) -> increase TPR
ALL INCREASE BP
22
Negative feedback control examples
hemorrhage
exercise
23
