Cardiovascular Physiology: Understanding the Heart, Blood, and Blood Vessels - Prof. James, Study notes of Physiology

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Chapter 12:

Cardiovascular

Physiology

Circulatory System

• (^) Three basic components:
  • (^) Heart - serves as pump that establishes

the pressure gradient needed for blood

to flow to tissues

• (^) Blood - transport medium within which

materials being transported are

dissolved or suspended

• (^) Blood vessels - passageways through

which blood is distributed from heart to

all parts of body and back to heart

Generalized Structure of Blood Vessels Arteries and veins are composed of … 1.Lumen - central blood-containing space surrounded by tunics 2.Tunics

• (^) Tunica interna (tunica intima) - Endothelial layer that lines the lumen of all vessels
• (^) Tunica media - Smooth muscle and elastic fiber layer, regulated by sympathetic nervous system - (^) Controls vasoconstriction/vasodilation of vessels
• (^) Tunica externa (tunica adventitia) - 1.Collagen fibers that protect and reinforce vessels

Generalized Structure of Blood Vessels

Capillaries

• (^) Capillaries are the smallest blood vessels
  • (^) Walls consisting of a thin tunica interna, one cell thick
  • (^) Allow only a single RBC to pass at a time
• (^) Movement of substances
  • (^) Lipid soluble- across cell membrane
  • (^) Water soluble- vesicle transport (transcytosis)
  • (^) Water, Ions, Gases- paracellular transport- through pores

Blood Flow Through Capillary Beds

• (^) Blood flow is regulated by vasomotor nerves and local chemical conditions, so it can either bypass or flood the capillary bed
• (^) Precapillary sphincter
  • (^) Cuff of smooth muscle that surrounds each

true capillary

• (^) Regulates blood flow into the capillary
• (^) All cells within body are close to a capillary
• (^) Only 5% of capillaries are open at one time

Venous System

• (^) Venules- are formed when capillary beds unite; Postcapillary venules –composed of endothelium
• (^) Large venules have one or two layers of smooth muscle (tunica media)
• (^) Veins- are formed when venules converge
  • (^) Composed of three tunics, with a thin tunica media and a thick tunica externa consisting of collagen fibers and elastic networks
  • (^) Capacitance vessels (blood reservoirs) that contain 65% of the blood supply
• (^) Veins have much lower blood pressure and thinner walls than arteries
• (^) To return blood to the heart, veins have special adaptations
  • (^) Large-diameter lumens, which offer little resistance to flow
  • (^) Valves (resembling semilunar heart valves), which prevent back-flow of blood

Venous System

Blood Pressure

• (^) Systolic Pressure results from blood forced into the arteries during ventricular systole.
• (^) Diastolic Pressure is the pressure in the arteries during ventricular diastole.
• (^) What is normal blood pressure? 120/

Blood Pressure

• (^) The pumping action of the heart

generates blood flow through the

vessels along a pressure gradient,

always moving from higher- to lower-

pressure areas

• (^) Systemic pressure:
  • (^) Is highest in the aorta
  • (^) Declines throughout the length of the

pathway

• (^) Is 0 mm Hg in the right atrium
• (^) The steepest change in blood pressure

occurs in the arterioles

Physics of Circulatory System

• (^) Law of Bulk Flow : Q = ΔP / RP / R
• (^) Meaning…
  • (^) For every increase or decrease in pressure

(ΔP) there is a proportional change in flow P) there is a proportional change in flow

(Q). (EX: increase pressure-->increase in

flow).

• (^) For every increase or decrease in

resistance there is a inverse change in

flow (Q). (EX: increase in resistance--

>decrease in flow)

Physics of Circulatory System

• (^) Law of Bulk Flow : Q = ΔP / RP / R
• (^) Substitute R for 8Lη / πrr^4
  • (^) L = length of the tube
  • (^) η (eta) = viscosity of the fluid
  • (^) r = radius of the tube
• (^) Poiseuille’s equation: Q = ΔP / RPπrr^4 / 8Lη
• (^) Meaning…
  • (^) For every increase or decrease in pressure (ΔP) there is a proportional change in flow P) or tube radius there is a proportional change in flow (Q). (EX: increase in pressure/tube radius--> increase in flow)
  • (^) For every increase or decrease in tube length or viscosity there is a inverse change in flow (Q). (EX: increase in tube length/viscosity-->decrease in flow)
• (^) Vasoconstriction or Vasodilation? know principles & formula