Which list accurately describes the pumps and channels that regulate the resting membrane potential and conduction in cardiac muscle cells?

Which list accurately describes the pumps and channels that regulate the resting membrane potential and conduction in cardiac muscle cells?

• A. Na+/K+ pumps and voltage-gated calcium channels
• B. Na+/K+ pumps, Ca2+ pumps, Na+ leak channels, and K+ leak channels
• C. Sodium leak channels only
• D. Chloride pumps and pumps

Answer: (B)

The resting membrane potential and propagation of electrical signals in cardiac muscle are governed by ion gradients and how permeable the cell membrane is to those ions at rest. The Na+/K+ pump maintains the essential gradients by moving Na+ out and K+ in, keeping the interior negative and ready for depolarization. At rest, K+ leak channels allow potassium to leak out, which drives the cell toward its negative resting potential, while Na+ leak channels introduce a small inward current that prevents the potential from becoming too negative and helps set baseline excitability. Calcium pumps actively remove Ca2+ from the cytosol after each beat, preserving Ca2+ homeostasis that influences relaxation, refractory properties, and how readily the cell can respond to subsequent stimuli—thereby shaping conduction. Together, these pumps and leak channels provide the primary controls for resting potential and the timing of electrical spread in the heart. Voltage-gated calcium channels drive the depolarization and plateau phases during an action potential rather than setting the resting potential, and chloride systems are not the main determinants of resting potential in cardiac tissue, so they don’t describe the full regulatory picture.

The resting membrane potential and propagation of electrical signals in cardiac muscle are governed by ion gradients and how permeable the cell membrane is to those ions at rest. The Na+/K+ pump maintains the essential gradients by moving Na+ out and K+ in, keeping the interior negative and ready for depolarization. At rest, K+ leak channels allow potassium to leak out, which drives the cell toward its negative resting potential, while Na+ leak channels introduce a small inward current that prevents the potential from becoming too negative and helps set baseline excitability. Calcium pumps actively remove Ca2+ from the cytosol after each beat, preserving Ca2+ homeostasis that influences relaxation, refractory properties, and how readily the cell can respond to subsequent stimuli—thereby shaping conduction. Together, these pumps and leak channels provide the primary controls for resting potential and the timing of electrical spread in the heart. Voltage-gated calcium channels drive the depolarization and plateau phases during an action potential rather than setting the resting potential, and chloride systems are not the main determinants of resting potential in cardiac tissue, so they don’t describe the full regulatory picture.