Final answer:
The resting neuron has a negative charge due to a difference in ion concentration across its membrane, primarily maintained by the sodium-potassium pump and the greater permeability for potassium to leave the cell, creating a resting membrane potential of about -70 mV.
Step-by-step explanation:
Resting Membrane Potential :
The resting neuron, or resting potential, refers to the electrical charge across the plasma membrane when the neuron is not transmitting a signal. In this state, the inside of the cell has a negative charge as it is approximately 70 millivolts more negative than the outside, denoted as -70 mV. This resting membrane potential is primarily due to the selective permeability of the neuronal membrane and the active transport of ions, particularly through the sodium-potassium pump.
The sodium-potassium pump works to maintain this potential by expelling three Na+ ions out of the cell while bringing in two K+ ions against their concentration gradient, at the expense of ATP, which the neuron consumes. This pump helps to establish a higher concentration of Na+ outside the cell and a higher concentration of K+ inside the cell. The cell's membrane has more potassium leakage channels, allowing K+ to move out of the cell more readily than Na+ can enter. This flow of potassium out of the cell and sodium into the cell is vital to the cell's ability to respond to stimuli. The net movement of these ions contributes to the negative charge inside the neuron during its resting state.