Chapter 19, Lesson 4: Electrical and Contractile Activity of the Heart

Flashcards from Chapter 19, Lesson 4 of McGraw Hill Anatomy and Physiology, Tenth Edition, by Kenneth S. Saladin.

Heart cycles

Done through contraction and relaxation

Systole

The contraction of the heart

Diastole

The relaxation of the heart

Sinus rhythm

Normal heartbeat by the SA node, around 70-80 per minute

Ectopic focus

A region of spontaneous firing other than the SA node, may govern rhythm if damaged

Nodal rhythm (junctional rhythm)

A type of ectopic focus where the AV node sets the heart rate

SA node firing (Sinuatrial node firing)

Done through depolarization and repolarization to set off heartbeat, usually every 0.8 seconds

Electrocardiogram (ECG)

A composite of all action potentials of nodal and myocardial cells detected as a result of firing and signals; comprises of letters PQRST for marking

P wave

The intial depolarization of the atria to trigger an atrial systole

QRS complex

Depolarization of the ventricles, where ventricular systole begins shortly after

T wave

Repolarization of the ventricles immediately prior to diastole

Ventricular fibrillation

Random signals result in no pumping action, can result in myocardial infarction and fatality

Atrial fibrillation (AFib)

Weak rippling contraction in atria due to chaotic signals; atria fail to stimulate ventricles

Heart block

Failure of part of conduction system; includes bundle branch block and total heart block

Myocardial infarction

Commonly known as a heart attack; heart stops pumping action