When the Ca2+ levels drop:

Myosin LC is dephosphorylated by MLC phosphatase, causing muscle relaxation.

TLS Online TPP Program

#Id: 5302

#Unit 7. System Physiology – Animal

Atrial systole

The P wave is caused by spread of depolarization through the atria and is followed by atrial contraction.

TLS Online TPP Program

#Id: 5303

#Unit 7. System Physiology – Animal

Atrial systole 

Increase in atrial pressure is reflected back to the veins, it appears on the venous pulse record as the a wave.

TLS Online TPP Program

#Id: 5304

#Unit 7. System Physiology – Animal

Atrial systole 

ventricle is relaxed, & because the AV valve is open, the ventricle is filling with blood from the atrium, even prior to atrial systole.

TLS Online TPP Program

#Id: 5305

#Unit 7. System Physiology – Animal

When blood is actively ejected from the atrium to the ventricle through the open AV valves. The corresponding “blip” in ventricular pressure reflects this additional volume added to the ventricle from atrial systole.

TLS Online TPP Program

#Id: 5306

#Unit 7. System Physiology – Animal

Fourth heart sound (S4)

Not audible in normal adults

Heard in ventricular hypertrophy, where ventricular compliance is decreased

TLS Online TPP Program

#Id: 5307

#Unit 7. System Physiology – Animal

Isovolumetric Ventricular Contraction

Initiates contraction of the ventricles

Intraventricular pressure rises sharply as the myocardium presses on the blood in the ventricle