In cardiac pacemaker cells, there is a current, known as the funny current or If

Question

In cardiac pacemaker cells, there is a current, known as the funny current or If, that plays a critical role in generating spontaneous action potentials. The If channel conducts both sodium and potassium. Assuming that [K]o = 4 mM, [Na]o = 140 mM, [K]i = 150 mM, and [Na]i = 12 mM, that the potassium permeability in the channel is 1.5 times greater than the sodium permeability, and that the channel’s conductance is a constant 3 nS, calculate the reversal potential for this channel. Sketch the linear current-voltage relationship.

Explanation / Answer

Based on the given data, the equation for calculation of reversal potential for the Na+-K+ channel is as follows:

Where,

Substitute the above values in the equation:

Thus, the Reversal potential of the pump is – 168 mV.

2)

The Eeq of both ions is calculated as:

Where,

The current for Na+ is:

The current for K+ is:

Thus, the graph would look like:

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