Cardiac Action Potential Phases Quiz

Ventricular Action Potential

• The phase characterized by a balance between Na+ and Ca++ influx and K+ outflux is the plateau phase.
• The primary cause of the initial rapid depolarization is the rapid influx of Na+ ions.
• The phase that marks the late rapid repolarization is Phase 3.

Cardiac Muscle Characteristics

• The resting membrane potential is approximately -90mV.
• The property that ensures cardiac muscle cannot go into a sustained state of contraction is the refractory period.
• Isometric contraction, which involves an increase in tension without a change in muscle length, is a type of muscle contraction.

T-Tubules and Calcium Ion Entry

• The main function of T-tubules during cardiac action potential is to allow rapid transmission of the action potential to the sarcoplasmic reticulum.
• Impaired T-tubule calcium ion entry would lead to decreased cardiac muscle contraction.

Cardiac Conduction System

• The sinoatrial (SA) node is known as the pacemaker.
• The primary characteristic of rhythmicity in cardiac muscle is the ability to generate rhythmic electrical impulses spontaneously.
• The Purkinje fibers are critical for spreading depolarization rapidly.
• The rate of autorhythmicity in Purkinje fibers is approximately 30-40 beats per minute.

Excitability and Ventricular Action Potential

• Excitability refers to the ability of a cell to respond to a stimulus and generate an action potential.
• Phase 0 of the ventricular action potential is characterized by rapid depolarization due to Na+ influx.
• The resting membrane potential (RMP) is the voltage at which the cardiac muscle is at rest.
• The main ionic basis of ventricular action potential is the influx of Na+ and Ca++ ions and the efflux of K+ ions.
• The property that allows excitable cells like cardiac muscle to transmit electrochemical impulses is excitability.
• Phase 1 of the ventricular action potential is characterized by early rapid repolarization due to K+ efflux.

Test your knowledge on the ionic basis of ventricular action potential phases in the heart. From the initial rapid depolarization to the late rapid repolarization, this quiz covers the key mechanisms involved in each phase.