Biology Notes

Resting Membrane Potential For the nervous system to function, neurons must be able to send and receive signals. These signals are possible because each neuron has a charged cellular membrane (a voltage difference between the inside and the outside), and the charge of this membrane can change in response to neurotransmitter molecules released from other neurons and environmental stimuli. To understand how neurons communicate, one must first understand the basis of the baseline or “resting” membrane charge. Neuronal Charged Membranes The lipid bilayer membrane that surrounds a neuron is impermeable to charged molecules or ions. To enter or exit the neuron, ions must pass through special proteins called ion channels that span the membrane. Ion channels have different configurations: open, closed, and inactive, as illustrated in Figure 1. Some ion channels need to be activated in order to open and allow ions to pass into or out of the cell. These ion channels are sensitive to ...

The membrane potential A resting (non-signaling) neuron has a voltage across its membrane called the  resting membrane potential , or simply the  resting potential . The resting potential 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  \text {Na}^+ Na + start text, N, a, end text, start superscript, plus, end superscript  and  \text K^+ K + start text, K, end text, start superscript, plus, end superscript . Ions move down their gradients via channels, leading to a separation of charge that creates the resting potential. The membrane is much more permeable to  \text K^+ K + start text, K, end text, start superscript, plus, end superscript  than to  \text {Na}^+ Na + start text, N, a, end text, start superscript, plus, end superscript , so the resting potential is close to the...