An axon joins the cell body at the axon hillock.
The synaptic terminal of one axon passes information across the synapse in the form of chemical messengers called neurotransmitters.
Information is transmitted from a presynaptic cell (a neuron) to a postsynaptic cell (a neuron, muscle, or gland cell).
Most neurons are nourished or insulated by cells called glia.
Structural diversity of neurons
Cell bodies of
Ion pumps and ion channels maintain the resting potential of a neuron
Every cell has a voltage (difference in electrical charge) across its plasma membrane called a membrane potential.
Messages are transmitted as changes in membrane potential.
The resting potential is the membrane potential of a neuron not sending signals.
In a mammalian neuron at resting potential, the concentration of K+ is greater inside the cell, while the concentration of Na+ is greater outside the cell.
Sodium-potassium pumps use the energy of ATP to maintain these K+ and Na+ gradients across the plasma membrane.
These concentration gradients represent chemical potential energy.
The opening of ion channels in the plasma membrane converts chemical potential to electrical potential.
A neuron at resting potential contains many open K+ channels and fewer open Na+ channels; K+ diffuses out of the cell.
Anions trapped inside the cell contribute to the negative charge within / inside the neuron.
The Basis of the Membrane Potential