11+B-Cardiovascular+Physiology

left ventricle

largest and strongest heart chamber

tricuspid valve

regulates blood flow between the right atrium and right ventricle

pulmonary valve

controls blood flow from right ventricle into the pulmonary arteries

mitral valve

lets oxygen-rich blood from the lungs pass from the left atrium into the left ventricle

aortic valve

opens the way for oxygen-rich blood to pass from the left ventricle into the aorta

systemic circulation

portion of the CV system which carries oxygenated blood away from the heart, to the body, and returns deoxygenated blood back to the heart

pulmonary circulation

portion of the CV system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated blood back to the heart

arteries

-deliver oxygenated blood to the tissues

-thick-walled, with extensive elastic tissue and smooth muscle

-under high pressure

-the blood volume contained in arteries is called stress volume

arterioles

-smallest branch site of arteries

-site of highest resistance in the CV system

-have a smooth muscle wall that is extensively innervated by autonomic nerve fibers

-arteriolar resistance is regulated by the ANS

-alpha-1 adrenergic receptors: found on arterioles of skin, splanchnic, and renal circulations

-beta-2 adrenergic receptors: found on arterioles of skeletal muscle

capillaries

-consist of a single layer of endothelial cells surrounded by basal lamina

-thin-walled

-site of exchange of nutrients, water, and gases

venules

-formed from merged capillaries

veins

-progressively merge to form larger veins

-thin-walled

-under low pressure

-contain the highest proportion of blood in the CV system

-blood volume contained in the veins is called the unstressed volume

-have alpha-1 adrenergic receptors

velocity of blood flow

V=Q/A

V: velocity (cm/sec)

Q: blood flow (mL/min)

A: cross-sectional (cm²)

velocity is directly proportional to blood flow and inversely proportional to the cross-sectional area at any level of the CV system

EX: BFV is higher in the aorta than in the sum of all of the capillaries. The lower velocity of blood flow in the capillaries optimizes conditions for exchange of substances across the capillary wall

blood flow

Q=P/R OR Cardiac Output=mean arterial pressure-right atrial pressure/total peripheral resistance (TPR)

Q: flow or cardiac output (mL/min)

P: pressure gradient (mmHg)

R: resistance or total peripheral resistance (mmHg/mL/min)

-pressure gradient (P) drives blood flow from high to low pressure

-blood flow is inversely proportional to the resistance of the blood vessels

Poiseuille’s equation

R=8nl/r^4

R: resistance

n: viscosity of blood

l: length of blood vessel

r^4: radius of blood vessel to the fourth power

resistance is directly proportional to viscosity of blood and to the length of the vessel

capacitance (compliance)

-describes the distensibility of blood vessels

-inversely related to elastance

C=V/P

C: capacitance or compliance (mL/mmHg)

V: volume (mL)

P: pressure (mmHg)

-directly proportional to volume and inversely proportional to pressure

-describes how volume changes in response to a change in pressure

-is much greater for veins than for arteries

-decreases with age

pressure profile in blood vessels

-as blood flows through the systemic circulation, pressure decreases progressively because of the resistance to blood flow

-pressure is highest in the aorta and lowest in the vena cava

-the largest decrease occurs across the arterioles because thry are the site of highest resistance

mean pressure in the systemic circulation:

1) aorta, 100 mmHg

2) arterioles, 50 mmHg

3) capillaries, 20 mmHg

4) vena cava, 4 mmHg