Lecture 22 Cardiovascular system 3 vessels, flow & pressure Flashcards
Arteries
conducting vessels high pressure thick walls elastic arteries "pressure reservoirs" muscular arteries smooth muscle, endothelium, elastic tissue, fibrous tissue
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)
Capillaries
exchange vessels microscopic very thin walls fluid filters out/in permeability: continuous< fenestrated <sinusoid Endothelium
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
Overall circuit is arranged in
series
pressure drops continuously from arteries to capillaries to veins
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
Blood flow and blood pressure
Flow = deltaP/R
Cardiac output, blood pressure, resistance
Cardiac output
CO= total blood flow CO= SV X HR
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
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
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
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
Total Peripheral Resistance
TPR
is the resistance of ENTIRE systemic circuit
Vasodilation is _ while vasoconstriction is _
locally controlled
sympathetic alpha adrenergic
Arterial BP
MAP= CO x TPR (relationship of factors that determine BP)
normal MAP is about 90 mm Hg
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
Blood volume is determined by
fluid intake vs fluid loss
Homeostatic control of blood pressure
Cardiovasular control center
arterial baroreceptors
Cardiovasular control center
located in the medulla oblongata
increases inputs from sensory receptors and higher brain centers
activates autonomic NS to regulate BP
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
sympathetic nervous system effects
high HR (B1) -> increase CO high contractility (B1) -> increase CO increased vasoconstriction (a1) -> increase TPR ALL INCREASE BP
Negative feedback control examples
hemorrhage
exercise
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
