Question

Describe the biological (ions) mechanism behind cardiac muscle cell depolarizing

Answer 1

Cardiac muscle cell depolarization involves prepotential depolarization and the movement of sodium, calcium, and potassium ions through specific ion channels.

Step-by-step explanation:

Cardiac muscle cells depolarize through a process called prepotential depolarization. This occurs when sodium ions diffuse through always-open sodium ion channels, causing the membrane potential to rise. This spontaneous depolarization is responsible for the autorhythmicity properties of cardiac muscle.

During the action potential, voltage-gated channels rapidly open, leading to a rapid influx of positively charged ions and a rise in membrane potential. This is followed by a plateau phase, where slow calcium channels open, allowing calcium ions to enter the cell. This results in a slow decline of the membrane potential. Finally, repolarization occurs when potassium channels open, allowing potassium ions to exit the cell.

In summary, cardiac muscle cell depolarization involves the movement of sodium, calcium, and potassium ions through specific ion channels, which leads to changes in the membrane potential.

Answer 2

Sure, the depolarization of cardiac muscle cells involves a sequence of ion movements, primarily sodium (Na+), potassium (K+), and calcium (Ca2+) ions. Here’s an outline of the process:

1. Resting potential: Cardiac muscle cells maintain a negative charge inside the cell relative to the outside. This is due to a higher concentration of potassium ions inside the cell and a higher concentration of sodium ions outside the cell. At rest, the membrane potential is about -90 mV.
2. Initiation of depolarization: When an electrical signal (action potential) reaches the cell membrane, it causes voltage-gated sodium channels to open. This allows an influx of sodium ions into the cell, causing the membrane potential to shift rapidly from negative to positive, initiating depolarization.
3. Peak of depolarization: As sodium ions continue to enter the cell, the membrane potential reaches its peak, typically around +20 to +30 mV.
4. Repolarization: After reaching its peak, voltage-gated sodium channels close, and voltage-gated potassium channels open. Potassium ions move out of the cell, leading to the restoration of the negative charge inside the cell and the repolarization of the membrane potential back to its resting state.
5. Calcium role: Calcium ions also play a crucial role in the excitation-contraction coupling of cardiac muscle cells. During depolarization, calcium ions enter the cell through specific channels. This influx of calcium triggers the release of more calcium from the sarcoplasmic reticulum, leading to the contraction of cardiac muscle fibers.

This coordinated movement of ions during depolarization and repolarization is essential for the generation of action potentials, which ultimately leads to the rhythmic contractions of the heart muscle.