chapter 14 physio

Cardiovascular system function

Transport of nutrients, gases, wastes, and signals

Closed circulatory system

Blood remains within vessels

Arteries definition

Carry blood away from heart

Veins definition

Return blood to heart

Heart chambers

Two atria and two ventricles

Pulmonary circulation

Right heart → lungs → heart

Systemic circulation

Left heart → body → heart

Driving force for blood flow

Pressure generated by ventricular contraction

Blood flow direction

From high pressure to low pressure

Pressure change over distance

Decreases as blood moves through vessels

Resistance factors

Length, viscosity, and radius

Most important resistance factor

Radius

Resistance vs flow

Inverse relationship

Flow equation

Flow proportional to pressure gradient

Flow rate

Volume of blood per time

Velocity

Distance blood travels per time

Velocity vs vessel size

Smaller vessels = higher velocity (at constant flow)

Cardiac muscle type

Striated muscle (myocardium)

Autorhythmic cells

Generate heart’s electrical signal

Coronary circulation

Supplies blood to heart muscle

Intercalated discs

Connect cardiac cells and allow signal spread

Gap junctions

Allow electrical signals between cells

Cardiac Ca2+ entry

Triggers Ca2+ release from SR

Force of contraction

Depends on Ca2+ entry

Cardiac AP depolarization

Na+ influx

Cardiac AP plateau

Ca2+ influx

Cardiac AP repolarization

K+ efflux

Pacemaker potential

Unstable membrane potential

Pacemaker ion channels

Allow positive ion influx

Autorhythmic depolarization

Ca2+ influx

Autorhythmic repolarization

K+ efflux

SA node

Pacemaker of heart

Signal pathway

SA → AV → bundle → Purkinje → muscle

Backup pacemakers

AV node or ventricles

ECG

P wave

ECG

QRS complex

ECG

T wave

Cardiac cycle

One contraction + relaxation cycle

Systole

Contraction phase

Diastole

Relaxation phase

End-diastolic volume (EDV)

Volume after filling

End-systolic volume (ESV)

Volume after contraction

Stroke volume

Blood pumped per beat

Ejection fraction

SV ÷ EDV

Cardiac output

HR × SV

Normal cardiac output

~5 L/min

AV valve function

Prevent backflow into atria

Semilunar valve function

Prevent backflow into ventricles

First heart sound

AV valve closure

Second heart sound

Semilunar valve closure

Isovolumic contraction

Pressure increases, volume unchanged

Ventricular ejection

Occurs when pressure exceeds arteries

Parasympathetic effect

Decreases heart rate

Sympathetic effect

Increases heart rate and force

Norepinephrine/epinephrine

Increase HR via β receptors

Acetylcholine

Decreases HR via muscarinic receptors

Frank-Starling law

↑ EDV → ↑ stroke volume

Preload

Determined by venous return

Venous return factors

Muscle pump, breathing, sympathetic tone

Contractility

Increased by catecholamines

Inotropic effect

Change in contractility

Afterload

Resistance heart must pump against

MAP

Indicator of afterload