Which of the following statements about the action potentials in contractile myo
ID: 227018 • Letter: W
Question
Which of the following statements about the action potentials in contractile myocardial cells (cardiac muscle) is INCORRECT?
Compared to skeletal muscle cells, contractile myocardial cells have a lower (more negative) resting membrane potential.
While cells in the SA node are autorhythmic and are able to generate action potentials without any outside stimuli, contractile myocardial cells require an outside stimulus to generate an action potential.
The duration of an action potential in a contractile myocardial cell is greater than the duration of an action potential in a typical neuron.
During the repolarization phase of a contractile myocardial action potential, the cell is highly permeable to sodium, potassium, and calcium.
Which of the following statements about the action potentials in contractile myocardial cells (cardiac muscle) is INCORRECT?
:Answers:1.
Compared to skeletal muscle cells, contractile myocardial cells have a lower (more negative) resting membrane potential.
2.While cells in the SA node are autorhythmic and are able to generate action potentials without any outside stimuli, contractile myocardial cells require an outside stimulus to generate an action potential.
3.The duration of an action potential in a contractile myocardial cell is greater than the duration of an action potential in a typical neuron.
4.During the repolarization phase of a contractile myocardial action potential, the cell is highly permeable to sodium, potassium, and calcium.
Explanation / Answer
All the given statements are correct except for the fourth one.
Resting potential of myocardial cell is -90mV compared to -70mV of skeletal muscle cell.
Contractile cells require external stimuli ,but SA node cells are autostimulatory.
Action potential lasts for 200-500ms for myocardial cell, compared to 4-6ms of neuron.
During repolarization, Ca2+ channels close. Incorrect: During the repolarization phase of a contractile myocardial action potential, the cell is highly permeable to sodium, potassium, and calcium.Related Questions
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