action potential in a cardiac muscle

• Resting Membrane Potential: 

  • A cardiac muscle cell starts with a resting charge of about -90 mV
  • the inside of the cell is negatively charged compared to the outside
• Depolarisation:

  Excitation: The cell becomes excited when the heart's electrical signal (action potential) arrives. 
• Sodium Influx:

  • excitation opens Na gated channels that allows positively charged Na+ to enter the cell

  • the inside is less negative and more positive. This is called depolarisation
• Plateau Phase: Potassium Efflux: 

  • While the cell is excited, potassium gated channels let positively charged K+ leave the cell.

  • This partially counters depolarisation.

  • Calcium Influx: Simultaneously, some calcium ions (Ca2+) enter the cell, keeping it in an excited state and prolonging the contraction.
• Repolarisation: Potassium Efflux Continues: 

  •As the action potential ends, potassium ions keep flowing out of the cell, making the inside negative again. 
• Calcium Channels Close: 

  The calcium channels that allow calcium influx to close, reducing calcium inside the cell. 
• Membrane Potential Returns to Resting State: 

  The cell's charge returns to its resting state of about -90 mV, ready for the next action potential.
• The action potential in cardiac muscle cells is unique because the plateau phase helps the heart contract for a longer time, ensuring efficient blood pumping. This rhythmic process keeps our heart beating and ensures blood circulation.