Cardiac Muscle and Heart Function

These flashcards cover key concepts regarding cardiac muscle structure, function, electrical behavior, and heart physiology.

Atrioventricular (AV) bundle

The pathway between the atria and ventricles, forks into right and left bundle branches.

Purkinje fibers

Large diameter nerves from bundle branches that distribute electrical excitation throughout the ventricular myocardium.

Cardiac muscle

Striated muscle with myocytes that pass signals from cell to cell, centrally placed nucleus, and features like intercalated discs for cell communication.

Skeletal muscle

Striated, multinucleated muscle with a more developed sarcoplasmic reticulum and smaller mitochondria compared to cardiac muscle.

Aerobic respiration

The process that cardiac muscle depends on for ATP, rich in myoglobin.

Sinus rhythm

Normal heart rate generated by the SA node, typically between 60-100 bpm.

Arrhythmia

An abnormal heart rhythm, which can include premature ventricular contractions (PVCs) due to firing other than the SA node.

Depolarization

The process where the resting potential of -60 mV is changed due to the influx of sodium (Na+) ions.

Plateau phase

Stage of the action potential where calcium (Ca2+) channels open leading to prolonged contraction.

Repolarization

The phase where potassium (K+) channels open, returning the membrane potential back to negative after contraction.

Ectopic focus

Firing of action potential from a site other than the SA node, like the AV node or Purkinje fibers.

Fibrillation

A condition of uncoordinated and out-of-phase contractions of the heart muscle.

Heart block

Failure of the cardiac conduction system leading to ventricles beating at their own pace.