Cardiovascular

QI am having a hard time understanding exactly what is happening with Ohmic vs. Inward and outward rectifying currents.

A

Ohm's law states that current = voltage/resistance or I = V/R

Currents which obey Ohm's law would behave like this graph where voltage changes directly with current and the slope is resistance.

 

In some cases, currents do not obey Ohm’s law and are not linear.  Like a light bulb where the resistance changes as the bulb filament heats up:

 

In the heart, some of the ion currents; e.g., inward rectifying potassium current do not obey Ohm’s law.

 

This is not that important in terms of function of the heart or ECG.  It does show up in the myocyte action potential as the phase 1 component.  This is due to outward flow of K through these transiently activated K channels. 

 

You won’t need to know any more about these. 

You do need to know which ion currents are active in different phases of the slow and fast action potentials.