3. The absolute refractory period in ventricular m

[Editor]

3. The absolute refractory period in ventricular muscle:

a. is the phase of the cardiac cycle when the heart cannot be stimulated by any stimulus however strong
b. is the same the same as the duration of the action potential
c. is longer than the refractory period in skeletal muscle
d. lasts approximately as long as the ventricular contraction
e. is always twice the S-T interval in the ECG

[anayas]

mark wrote:

3. The absolute refractory period in ventricular muscle:

a. is the phase of the cardiac cycle when the heart cannot be stimulated by any stimulus however strong
b. is the same the same as the duration of the action potential
c. is longer than the refractory period in skeletal muscle
d. lasts approximately as long as the ventricular contraction
e. is always twice the S-T interval in the ECG

a T b T c T d T e

The Refactory period - period during and following action potential in which the neurone is insensitive to further stimulation. Subdivided into:
Absolute - excited by no stimulus, however strong
Relative - excitation may occur following a greater than normal stimulus

The ventricular muscle AP lasts 250msec, Abs refactory period lasts 200msec and the relative refactory period 50msec. The refactory period extends into phase 3 of the AP.

The long refactory period means that it is impossible to summate contractions and tetansie heart muscle.

[andrewsdavid]

the absolute refactory period cannot be as long as the action potential, may be the total refractory period may be as long as the action potentia.