Question

Explain how the regulation of ion permeability leads to the properties of cardiac muscle.

Explain how and ECG reading could be used to diagnose abnormalities of cardiac function.

Answer 1

Dear Student ,

First of all, Ions are the charged atoms, the movements of which leads to the changes in membrane potential across the cell membrane of cardiac cells which leads to Cardiac action potential . This cardiac action potential arises from the Sinoatrial Node (found in the Right Atrium) and it is also known as pacemaker of heart. All the muscle cells of heart are linked by Gap junctions. And the main Ions impacting the properties of cardiac muscle are Na+,K+,Ca+2,Cl-.

Action of Ion channels on Cardiac Action potential :

Phase 0: This is caused by activation of Na+ channels leading to slight increase of voltage within the cell and when it reaches threshold potential of -70mV Na+ ion channels open and there is increase in sodium inflow which further increases the voltage to +50 mV.

Phase 1: this is due to inactivation of sodium channels and thus decreases the sodium inflow into the cell. And also K+ channels allows the flow of K+ ions out of the cell,making membrane potential slightly more negative.

Phase 2( Plateau phase) : Balanced phase as the ion movements in this phase maintains the membrane potential constant.

Phase 3: This is Rapid Repolarization phase.It begins by Ca+2 channel closure and The K+ Channels remain open.

Phase 4: This period is Diastole and the cells are in rest in this phase. And the cycle continues.

❤ECG (Electrocardiogram) :

This medical test is due to record the Cardiac Action potential. ECG consists of series of upward spikes and downward spikes namely P, Q, R, S, T. and any change in this representation warns an abnormality of cardiac function.

In the picture provided,  I have explained ECG spikes and mentioned about some abnormalities which can be detected through ECG .

Hope you are clear...!