Chapter 19, Lesson 5: Blood Flow, Heart Sounds, and the Cardiac Cycle

Flashcards from Chapter 19, Lesson 5 of McGraw Hill Anatomy and Physiology, Tenth Edition, by Kenneth S. Saladin.

Cardiac cycle

The complete contraction and relaxation of all four chambers of the heart

Pressure

The principal cause of blood flow

Resistance

The opposition to blood flow

Pressure gradient

Required for blood flow from high to low; higher volumes mean lower pressure and vice versa

Valvular insufficiency (incompetence)

Any failure of a valve to prevent reflux, or the backward flow of blood

Valvular stenosis

Where the cusps of the heart are stiffened and constricted by scar tissue; regurgitation is heard as a murmur

Mitral valve prolapse

Insufficiency in which one or both mitral valve cusps bulge into the atria during ventricular contraction

Auscultation

Listening to sounds made by the body

First heart sound (S1)

The closure of the AV valves’ sound causing the movements of the heart wall (a “lubb”)

Second heart sound (S2)

The closure of semilunar valves (pulmonary and aortic) and movements of the heart wall

Third heart sound (S3)

Rarely heard in people over 30; may indicate enlarged or failing heart

Cardiac cycle phases

1. Ventricular filling

2. Isovolumetric contraction

3. Ventricular ejection

4. Isovolumetric relaxation

Ventricular filling

The first step in the cardiac cycle where ventricles expand and blood flows into the ventricles from the atria

Isovolumetric contraction

The second step in the cardiac cycle where atria repolarize, ventricles depolarize, and S1 occurs with the QRS complex

Ventricular ejection

The third step in the cardiac cycle where semilunar valves open and ejection occurs, causing the T wave later on

Isovolumetric relaxation

The fourth step in the cardiac cycle where semilunar valves close and S2 occurs; sets up AV valves to refill and restart cycle

Congestive heart failure (CHF)

The failure of either ventricle to eject blood effectively; left failure can result in a pulmonary edema and right failure can cause a general edema