Cardiac refractory period

Question 1

an excessive heart rate provides insufficient time for ____ ____. When this occurs ____ ____ falls and death may occur. What is protection against this provided by?

Answer 1

cardiac filling
cardiac output
refractory period of cardiac myocytes

Question 2

What is the refractory period of the heart?

Answer 2

the interval of time during which a normal cardiac impulse cannot re-excite an already excited area of cardiac muscle.

Question 3

How long does the normal refractory period of the ventricle last? what does this correspond to the duration of?

Answer 3

from 250 to 300 milliseconds

Corresponds to the duration of the action potential

Question 4

There is an additional relative refractory period. How long does this period last roughly and how is it different from the normal refractory period?

Answer 4

50 milliseconds

During this period the muscle is more difficult than normal to excite, but nevertheless can be excited.

Question 5

The long (normal) refractory period ensures that cardiac muscle _______ and _______ are almost complete before the next _____ _____ is initiated. Thus ______ contraction is prevented in cardiac muscle.

Answer 5

contraction
relaxation
action potential
tetanic