Cardiac Action Potential: Multiple Choice Questions

Group 1

• Phase 0 - Rapid depolarization

• Phase 1 - Initial repolarization

• Phase 2 - Plateau

• Phase 3 - Rapid repolarization

• Phase 4 - Resting potential

• Phase 5 - Hyperpolarization

• Sodium (Na+)

• Potassium (K+)

• Calcium (Ca2+)

• Chloride (Cl-)

• Magnesium (Mg2+)

• Rapid influx of Na+ ions

• Efflux of K+ ions

• Influx of Ca2+ ions

• Efflux of Cl- ions

• Influx of Mg2+ ions

• Phase 0

• Phase 1

• Phase 2

• Phase 3

• Phase 4

• Efflux of K+ ions

• Influx of Na+ ions

• Influx of Ca2+ ions

• Efflux of Cl- ions

• Influx of Mg2+ ions

• It is longer than the action potential in skeletal muscle.

• It involves a plateau phase.

• It does not involve calcium ions.

• It is shorter than the action potential in neurons.

• It is initiated by the opening of potassium channels.

• Contributes to the plateau phase

• Triggers muscle contraction

• Causes rapid depolarization

• Causes rapid repolarization

• Is not involved in the cardiac action potential

• Voltage-gated sodium channels

• Voltage-gated potassium channels

• Voltage-gated calcium channels

• Ligand-gated chloride channels

• Voltage-gated magnesium channels

• Maintained by the Na+/K+ pump

• Negative inside relative to outside

• Positive inside relative to outside

• Maintained by the Ca2+ pump

• No ion movement occurs

• Prevents tetanus in cardiac muscle

• Allows time for the heart to refill with blood

• Allows for rapid successive action potentials

• Increases the strength of contraction

• Decreases the strength of contraction

• Heart rate

• Ion channel mutations

• Temperature

• Blood pressure

• Oxygen levels

• It helps maintain the resting membrane potential.

• It pumps 3 Na+ out and 2 K+ in.

• It pumps 2 Na+ out and 3 K+ in.

• It is active during the action potential.

• It does not require ATP.

• Closure of Na+ channels

• Opening of K+ channels

• Opening of Ca2+ channels

• Closure of K+ channels

• Opening of Na+ channels

• Phase 2

• Phase 0

• Phase 1

• Phase 3

• Phase 4

• It is due to the influx of Ca2+ ions.

• It prolongs the action potential.

• It is due to the efflux of Na+ ions.

• It shortens the action potential.

• It occurs during Phase 3.

• Responsible for repolarization

• Contributes to resting membrane potential

• Causes depolarization

• Responsible for the plateau phase

• Not involved in the action potential

• It prevents the heart from undergoing tetanus.

• It ensures unidirectional propagation of the action potential.

• It allows for immediate re-excitation of the heart muscle.

• It shortens the duration of the action potential.

• It is not present in cardiac cells.

• Influx of Ca2+ ions

• Efflux of K+ ions

• Influx of Na+ ions

• Efflux of Na+ ions

• Influx of Cl- ions

• Decrease the duration of the plateau phase

• Reduce the force of cardiac contraction

• Increase the rate of depolarization

• Increase the duration of the plateau phase

• Increase the force of cardiac contraction

• Na+ influx causes rapid depolarization

• K+ efflux causes repolarization

• Ca2+ influx contributes to the plateau phase

• Cl- influx causes depolarization

• Mg2+ influx contributes to the plateau phase

• Increases intracellular calcium

• Increases the force of contraction

• Decreases the duration of the action potential

• Decreases intracellular sodium

• Decreases the force of contraction

• Responsible for the rapid depolarization phase

• Contributes to the plateau phase

• Responsible for repolarization

• Not involved in the action potential

• Contributes to the resting membrane potential

• Decreases the resting membrane potential

• Increases the excitability of cardiac cells

• Increases the resting membrane potential

• Decreases the excitability of cardiac cells

• Has no effect on cardiac action potentials

• Prolongs the duration of the action potential

• Decreases the force of contraction

• Shortens the duration of the action potential

• Increases the force of contraction

• Has no effect on cardiac action potentials

• Sympathetic stimulation increases heart rate

• Parasympathetic stimulation decreases heart rate

• Sympathetic stimulation decreases heart rate

• Parasympathetic stimulation increases heart rate

• The autonomic nervous system has no effect on heart rate