18 Questions
During which phase of the cardiac action potential does the absolute refractory period mainly occur?
Phase 0
What is the significance of the long refractory period of cardiomyocytes in relation to muscle contraction?
Prevents the heart from being tetanized
Which type of channels are primarily responsible for the rapid depolarization in Phase 0 of the cardiac action potential?
Fast Na+ channels
What characterizes the relative refractory period in cardiomyocytes?
Requires a stronger stimulus to elicit a response
Why can't the heart be tetanized unlike skeletal muscle?
Presence of gap junctions between cardiac myocytes
How does the long refractory period of cardiomyocytes contribute to the pumping function of the heart?
Limits sustained muscle contractions
During which phase of the action potential do Na+ channels recover and become capable of reopening?
Phase 1
Why do cardiomyocytes have a longer refractory period compared to skeletal muscle cells?
Due to the presence of slow Ca2+ channels in cardiomyocytes
What defines the Absolute Refractory Period in the cardiac muscle?
The period when Na+ channels are closed
What is the mechanical response during the Absolute Refractory Period?
Systole and early diastole
What characterizes the Relative Refractory Period in cardiac muscle?
Reduced sensitivity to additional stimulation
What is the key difference between Absolute and Relative Refractory Periods?
Sensitivity to stimulation
What is the interval of time during which a normal cardiac impulse cannot re-excite an already excited area of cardiac muscle known as?
Absolute refractory period
Which property describes the ability of the cardiac muscle to generate an action potential followed by contraction?
Excitability
What is the term for the feature of the cardiac muscle that makes it capable of responding to an adequate stimulus?
Excitability
Which of the following principles states that once a threshold stimulus is reached, the cardiomyocyte responds with a complete contraction?
All-or-None principle
During which period does the cardiac muscle have reduced excitability but could respond to a very strong stimulus?
Relative refractory period
Which term describes the ability of the heart muscle to transmit electrical impulses efficiently?
Conductivity
Test your knowledge on the cardiac muscle refractory period and the factors affecting it. Learn about the different degrees of refractoriness encountered during an action potential in cardiomyocytes. Explore the relationship between fast Na+ channels recovery and depolarization in cardiac muscle cells.
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