The process where the heart muscle conducts an electrical impulse causing a contraction is called depolarization. True or false?
The correct answer and explanation is:
Correct Answer: True
Explanation:
The statement is True: The process where the heart muscle conducts an electrical impulse causing a contraction is called depolarization.
In the context of cardiac physiology, depolarization refers to the electrical activation of heart muscle cells (cardiomyocytes). This process occurs when the resting membrane potential of a cardiac cell becomes more positive due to the rapid influx of sodium (Na⁺) ions through specialized ion channels in the cell membrane. This electrical change spreads through the heart, triggering the muscle fibers to contract.
Here’s how it works in steps:
- Resting State: Heart cells are normally negatively charged inside relative to the outside (polarized state).
- Depolarization: When a stimulus (such as from the sinoatrial [SA] node—the heart’s natural pacemaker) reaches a heart cell, it opens sodium channels, allowing Na⁺ to rush in. This makes the inside of the cell temporarily more positive (less negative), which is the depolarization phase.
- Contraction: As depolarization spreads across the heart muscle, it causes calcium (Ca²⁺) channels to open, and calcium floods into the cells. Calcium is crucial for initiating the interaction of actin and myosin fibers, leading to muscle contraction.
- Repolarization: After contraction, potassium (K⁺) exits the cell, restoring the negative internal charge and returning the cell to its resting state. This phase is called repolarization and is essential for the heart muscle to relax and be ready for the next impulse.
Depolarization can be observed in an electrocardiogram (ECG) as the P wave (atrial depolarization) and QRS complex (ventricular depolarization).
In summary, depolarization is the electrical event that directly causes the mechanical event of contraction in the heart muscle, making the statement true.