In an excitable cell such as the neuron, an equilibrium potential is achieved wh

Question

In an excitable cell such as the neuron, an equilibrium potential is achieved when: (A)Na+ influx increases (B) K+ efflux increases the concentration force for K+ is counteracted by the electric force of repulsion (D) A, B and C (E) Ca^+2 efflux increases Which of the following is NOT true about an action potential? (A) is evoked when the resting potential is established (B) is evoked when the threshold potential is reached (C) it is "all or none" (D) Ca^+2 will flow into the cell at this time (E) it will last about 1 ms

Explanation / Answer

The equilibrium potential in a cell is determined by concentration gradients of ions across the membrane and by membrane permeability to each type of ion.

In a resting neuron, there are concentration gradients across the membrane for Na+ and K+ ions.

The membrane is much more permeable to K+ than to Na+, so the resting potential is close to the equilibrium potential of K+. The equilibrium potential of K+ is established when the concentration of K+ is counteracted by the electric force of repulsion.

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