Question

In: Anatomy and Physiology

Refractory period. A)Which heart cells have a refractory period in their action potential? B)How is the...

Refractory period.

A)Which heart cells have a refractory period in their action potential?

B)How is the prolonged refractory period generated in cardiac muscle?

C) what is the advantage of a prolonged refractory period?

D) would you recommend a drug that prolongs or shortens plateau phase of the cardiac muscle cell action potentials for patients with tachycardia? Explain why.

Expert Solution

Refractory period is the time taken for an excitable membrane to be ready for a second stimulus once it returns to its resting state following an excitation.

Cardiac cells have two refractory periods, the first from the beginning of phase 0 until part way through phase 3; this is known as the absolute refractory period during which it is impossible for the cell to produce another action potential. This is immediately followed, until the end of phase 3, by a relative refractory period, during which a stronger-than-usual stimulus is required to produce another action potential.

Which heart cells have a refractory period in their action potential?

Contractile cells

B. )How is the prolonged refractory period generated in cardiac muscle?

During the Effective Refractory Period, stimulation of the cell by an adjacent cell undergoing depolarization does not produce new, propagated action potentials. This occurs because fast sodium channels remain inactivated following channel closing during phase 1. They do not change to their closed, resting (excitable) state until some time after the membrane potential has fully repolarized.

Drugs that block potassium channels (e.g., amiodarone, a Class III antiarrhythmic) delay phase 3 repolarization and increases the Effective Refractory period.

C) what is the advantage of a prolonged refractory period?

Advantages of prolonged refractory period :

1)Ventricle gets time to relax between stimuli. Decreases heart rate

2)the heart can fill with blood before contracting again

3)the ventricle does not enter fibrillation

D) would you recommend a drug that prolongs or shortens plateau phase of the cardiac muscle cell action potentials for patients with tachycardia? Explain why.

A drug that prolong platue phase can be recommended for tachycardia

Prolonged platue phase prolongs duration of action potential and effective refractory period and decrease heart rate

Sydney Mullin answered 2 years ago

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