Question

Explain how what would be the physiological impact of tetanus to heart function and how contractile cardiomyocytes avoid tetanus./

Answer 1

Tetanus is defined as sustained muscle contraction, caused due to toxin released by tetani bacteria.

Cardiac muscle has specific features such as it has two type of cells - conducting cardiac cells which forms conduction system and contraction cardiac cells which forms contractile unit of heart.

Cardiac muscle has intercalated discs which allow passage of ions, molecules and impulse transmission. Cardiac muscle has longer refractory period. Membrane properties of cardiac muscle also differs from skeletal and smooth muscle.

Cardiac muscle has refractory period of 180-200 msec which is quite long and no other contraction takes place during this time, which provides adequate filling of heart and does not hinders pumping action of heart. Thus, longer refractory period is the property of cardiac muscle which prevents sustained contraction in cardiac muscle.

Longer refractory period is due to the prolonged inactivated state of voltage gated sodium channels.

If there would have been sustained contraction in heart muscle, death will occur as pumping action of the heart would be hampered.