Transcript Physiology of Circulation

Pages 382-390
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Alternating expansion and recoil of a blood
vessel wall (the pressure wave) that occurs as
the heart beats
Locate arterial pulse at “pressure points” in
superficial arteries
 These same points are used to stop blood flow due
to hemorrhage from injury
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Avg is 70-76 bpm at rest for a healthy person
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Superficial temporal artery
Facial artery
Common carotid artery
Brachial artery
Radial artery
Femoral artery
Popliteal artery
Posterior tibial
artery
Dorsalis pedis artery
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Blood pressure is: the pressure the blood exerts
against the inner walls of the blood vessels
Blood is forced along a descending pressure
gradient
◦ Pressure is highest in the large systemic arteries, lower
in the capillaries, and lowest in the veins

Elasticity of vessels is pertinent to healthy, elastic
arteries
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Systolic—pressure at the peak of ventricular
contraction
Diastolic—pressure when ventricles relax
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Expressed as systolic over diastolic
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◦ 120/80 mm Hg is average
◦ The brachial artery is used for measurement
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
Hypotension- low blood pressure (<100 sys.)
Hypertension- high blood pressure (>140/90)
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Resistance within blood vessels (increases)
Kidneys regulate blood volume via enzymes
Temperature1. cold causes vasoconstriction
2. Heat causes vasodilation
4.
Chemicals
1. Hormones like epinephrine
2. Drugs/nicotine
3. Diet
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
Gas and nutrient exchange occurs through
capillary walls
◦ Driven by concentration gradients
 Oxygen and nutrients go from blood to tissues
 Carbon dioxide and other wastes go from tissue to blood

Substances diffuse through the interstitial fluid
(tissue fluid) found between cells
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2.
3.
4.
Direct diffusion through membranes
Diffusion through intercellular clefts/gaps
Diffusion through pores
Transport via vesicles (bulk transport)
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Lumen of
capillary
Intercellular
cleft
Vesicles
pore
4 Transport
via vesicles
3 Diffusion
through pore
1 Direct
diffusion
through
membrane
2 Diffusion through
intercellular cleft/gap
Interstitial fluid
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Blood pressure forces fluid and solutes out
of capillaries at the arterial end
Osmotic pressure draws fluid into
capillaries at the venous end
At the arterial end, BP > OP
At the venous end, BP < OP
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Tissue cell
Interstitial fluid
Net fluid
movement
out
Net fluid
movement
in
Arterial
end of
capillary
Venule
end of
capillary
At the arterial end of
a capillary, blood
pressure is more than
osmotic pressure,
and fluid flows out of
the capillary and into
the interstitial fluid.
At the venule end of
the capillary, blood
pressure is less than
osmotic pressure,
and fluid flows from
the interstitial fluid
into the capillary.
Blood pressure is
higher than osmotic
pressure
Osmotic pressure
remains steady
in capillary bed
Blood pressure is
lower than osmotic
pressure