Ch.3: Heart Electrical Physiology

action potential

Rapid electrical signal that travels along a cell membrane.

afterload

Resistance the heart must overcome to eject blood.

atrial kick

Final push of blood from atria into ventricles before ventricular contraction.

automaticity

Ability of cardiac cells to generate impulses without stimulation.

bundle branches

Pathways that conduct electrical impulses through the ventricles.

bundle of His

Conduction fibers carrying impulses from AV node to bundle branches.

cardiac cycle

Complete sequence of one heartbeat: systole + diastole.

conductivity

Ability of cardiac cells to transmit electrical impulses.

contractility

Strength of cardiac muscle contraction.

depolarization

Electrical activation of cells causing contraction.

diastole

Relaxation phase when the heart fills with blood.

end diastolic volume

Amount of blood in the ventricle at the end of diastole.

end systolic volume

Amount of blood left in the ventricle after systole.

excitability

Ability of cardiac cells to respond to a stimulus.

extracellular

Outside the cell.

heart rate

Number of heartbeats per minute.

intracellular

Inside the cell.

internodal pathways

Atrial conduction routes carrying impulses from SA node to AV node.

peripheral vascular resistance

Resistance to blood flow in systemic blood vessels.

polarization

Resting electrical state of a cell before activation.

preload

Amount of ventricular stretch at the end of diastole.

pulse pressure

Difference between systolic and diastolic blood pressure.

Purkinje network

Final ventricular conduction fibers enabling coordinated contraction.

refractory period

Time when a cell cannot respond to a new stimulus.

repolarization

Return of the cell to its resting electrical state.

resting state

Baseline electrical condition before depolarization.

Starling’s Law of the Heart

Greater stretch of the ventricle increases contraction strength.

stroke volume

Amount of blood ejected by the ventricle per beat.

systole

Contraction phase when the heart pumps blood.