What is the threshold level for depolarization in cardiac cells?

What is the threshold level for depolarization in cardiac cells?

• A. About -70 mV
• B. About -60 mV
• C. About -80 mV
• D. About -90 mV

Answer: (B)

The threshold level for depolarization in cardiac cells is approximately -60 mV. This value is significant because it represents the point at which the membrane potential becomes sufficiently positive to activate voltage-gated sodium channels. When these channels open, sodium ions rush into the cell, causing a rapid depolarization that leads to the generation of an action potential. This process is crucial for the proper functioning of the heart, allowing for coordinated contractions and rhythm of the cardiac muscle. Understanding why this threshold is set around -60 mV involves knowing that cardiac action potentials differ from those in other types of excitable tissues, like neurons. Cardiac cells maintain a resting membrane potential more negative than this threshold, and reaching -60 mV is essential for triggering the heart's electrical activity. Thus, this specific threshold is vital for initiating the sequence of depolarization, followed by repolarization, which is necessary for each heartbeat.

The threshold level for depolarization in cardiac cells is approximately -60 mV. This value is significant because it represents the point at which the membrane potential becomes sufficiently positive to activate voltage-gated sodium channels. When these channels open, sodium ions rush into the cell, causing a rapid depolarization that leads to the generation of an action potential. This process is crucial for the proper functioning of the heart, allowing for coordinated contractions and rhythm of the cardiac muscle.

Understanding why this threshold is set around -60 mV involves knowing that cardiac action potentials differ from those in other types of excitable tissues, like neurons. Cardiac cells maintain a resting membrane potential more negative than this threshold, and reaching -60 mV is essential for triggering the heart's electrical activity. Thus, this specific threshold is vital for initiating the sequence of depolarization, followed by repolarization, which is necessary for each heartbeat.