At lower concentrations of activin, genes were not activated, and the “default” gene expression instructed the cells to become blood vessels and heart.

TLS Online TPP Program

#Id: 5256

#Unit 7. System Physiology – Animal

Contractile cells constitute the majority of atrial & ventricular tissues.

TLS Online TPP Program

#Id: 5257

#Unit 7. System Physiology – Animal

Conducting cells constitute tissues of the SA node, the atrial internodal tracts, the AV node, the bundle of His, & the Purkinje system.

TLS Online TPP Program

#Id: 5258

#Unit 7. System Physiology – Animal

Conducting cells are specialized muscle cells which function to rapidly spread action potentials over the entire myocardium.

TLS Online TPP Program

#Id: 5259

#Unit 7. System Physiology – Animal

The action potential spreads throughout the myocardium in the following sequence:

SA node  Atrial internodal tracts and atria  AV node  Bundle of His  Purkinje system  Ventricles

TLS Online TPP Program

#Id: 5260

#Unit 7. System Physiology – Animal

Myocardial fibers have a resting membrane potential of approximately –90 mV.

TLS Online TPP Program

#Id: 5261

#Unit 7. System Physiology – Animal

The individual fibers are separated by membranes, but depolarization spreads radially (syncytium) because of the presence of gap junctions.