Electrical Activity of the Heart

These flashcards cover key concepts related to the electrical activity of the heart, including the conduction system, action potentials, and cardiac cycle.

The ability of autorhythmic cells to generate their own rhythm is known as __.

Autorhythmicity

The conduction system of the heart includes the and nodes.

Sinoatrial (SA), Atrioventricular (AV)

The __ is responsible for the wave of excitation traveling from the SA node to the AV node.

Internodal pathway

At rest, the firing rate of the SA node is typically __ APs/min.

70-80

The __ phase causes K+ to rush out, repolarizing the pacemaker cells.

Repolarization

The threshold for firing action potentials in pacemaker cells is approximately __ mV.

-50 mV

During the cardiac action potential, Ca2+ channels opening leads to __ of the cell.

Depolarization

The cardiac cycle consists of a contraction phase called and a relaxation phase called .

Systole, Diastole

During ventricular filling, the pressure in the atria must be __ than the pressure in the ventricles.

Greater

The formula for stroke volume is __.

EDV - ESV

The cardiac output is calculated using the formula __.

CO = SV x HR

Epinephrine is a hormone that __ heart rate by increasing the frequency of firing in the SA node.

Increases

The Frank-Starling principle states that increased end-diastolic volume (EDV) stretches muscle fibers and results in __.

Increased stroke volume (SV)