Action potentials and neural communication

All-or-nothing principle

A neuron either fires a full action potential or does not fire at all.

Depolarization

The inside of a neuron becomes less negative, usually because positively charged sodium ions enter. This helps trigger an action potential.

Refractory period

The brief period after a neuron fires when it cannot fire again or is less likely to fire again.

Resting potential

The neuron's stable, negatively charged state when it is not firing, typically around −70 millivolts.

Reuptake

The process by which a sending neuron reabsorbs neurotransmitters from the synapse.

Threshold

The level of stimulation needed to trigger an action potential.

Multiple sclerosis (MS)

A disease in which the immune system damages myelin in the CNS, disrupting neural communication.

Myasthenia gravis

An autoimmune disorder that interferes with communication between nerves and muscles, causing muscle weakness.

Excitatory neurotransmitters

Chemical messengers that increase the likelihood that the receiving neuron will fire.

Inhibitory neurotransmitters

Chemical messengers that decrease the likelihood that the receiving neuron will fire.