Lecture 22 Cardiovascular system 3 vessels, flow & pressure Flashcards Preview

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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 Endothelium

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

Negative feedback for arterial blood pressure

variable - arterial blood pressure
sensor - baroreceptors (stretch receptors)& carotid and aortic arteries
input - 9th & 10th cranial nerves
integrating center - medulla oblongata
effectors - heart (CO) and vascular smooth muscle (TPR)
response