irat 3

Capillary

Microscopic single cell endothelial exchange vessel connecting arterioles to venules

Artery

Thick, elastic blood vessels carrying blood away from the heart under high pressure

Vein

Thin walled, high capacitance blood vessel returning blood to heart

Septum

Central muscular wall diving the heart into right and left halves

Pulmonary arteries

Arteries carrying deoxygenated blood to lungs

Veins

Return oxygenated blood to left atrium

Superior and inferior vena cava

Major systemic veins returning deoxygenated blood from the upper and lower body to right atrium

Aorta

Primary systemic artery carrying oxygen rich blood from left ventricle to body

Vasoconstriction

Decrease in vessel radius, and blood flow, higher resistance

Vasodilation

Increase in vessel radius, and blood flow, lower resistance

Pericardium

Tough, fluid filled membranous sac surround heart that lubricates beating

Myocardium

Thick middle layer of cardiac muscle forming bulk of heart wall

Systole

Contraction phase

Diastole

Relaxation phase of cardiac chambers

Arteriole

small muscular vessel that regulates resistance and directs blood flow to capillary beds

Venule

small convergent vessel that collects blood from capillaries and empties into veins

Endothelium

Inner monolayer of epithelial cells lining all blood vessels and cardiac chambers

Systolic Pressure

Highest arterial pressure during ventricular (120 mmHg)

Diastolic Pressure

lowest pressure during ventricular (80 mmHg)

Effect of increase in venous return on blood pressure

Stretches ventricles -> increases EDV -> increases SV (Starling's Law) -> increases CO -> increases BP

Effect of increase in blood volume on blood pressure

Fills vascular space -> increases venous return -> increases CO -> increases BP (and vice versa with blood loss).

Effect of increase in heart rate or increase in stroke volume on blood pressure

Directly increases cardiac output (CO = HR x SV) -> pumps more blood into arteries -> increases BP.

Effect of vasoconstriction vs. vasodilation on blood pressure

Vasoconstriction (decreased diameter) -> increases resistance (R proportional to 1/r^4) -> increases BP; Vasodilation (increased diameter) -> decreases resistance -> decreases BP.

Sympathetic vasoconstriction: receptor and target organs

alpha-1-adrenergic (via norepinephrine); constricts arterioles in GI tract, kidneys, and skin to divert blood away.

Sympathetic vasodilation: receptor and target organs

beta-2-adrenergic (via circulating epinephrine); dilates arterioles in skeletal muscle, heart (coronary), and liver.

Order of blood vessels in flow from the heart

Heart -> Arteries -> Arterioles -> Capillaries -> Venules -> Veins -> Heart

Relationship between blood vessel diameter and peripheral resistance

Inversely proportional to the 4th power (R proportional to 1/r^4); small drops in diameter cause massive spikes in resistance.

How arterioles direct blood flow to different tissues

Arranged in parallel as adjustable valves; constricting high-resistance paths diverts blood to lower-resistance paths

Complete pathway of blood flow through heart, lungs, and systemic circuit

Vena Cava -> RA -> Tricuspid -> RV -> Pulmonary Valve -> Pulmonary Arteries -> Lungs -> Pulmonary Veins -> LA -> Bicuspid (Mitral) -> LV -> Aortic Valve -> Aorta -> Tissues -> Vena Cava

Driving force of blood flow and relationship to pressure difference (delta P)

Blood flows high -> low pressure; flow rate is directly proportional to the pressure gradient (F proportional to delta P) regardless of baseline absolute pressure.

Fourth-power law calculations (R proportional to 1/r^4)

Doubling radius (2r) drops resistance to 1/16 (16x flow); halving radius (1/2r) increases resistance 16x (1/16 flow).

Function of heart valves vs. valve incompetence

Function: enforce unidirectional forward flow; Incompetence: failure to seal causes backward regurgitation, reducing pumping efficiency