Neurons: the brain's messengers
Every thought, feeling, and movement depends on billions of nerve cells signalling one another.
Parts of a neuron
A neuron receives signals through branching dendrites, combines them in the cell body (soma), and sends its own signal down a long axon to terminal buttons. Many axons are wrapped in a fatty myelin sheath that speeds transmission. Glial cells support neurons by providing nutrients, insulation, and cleanup.
The action potential
A resting neuron holds a negative charge inside. When incoming signals push it past a threshold, channels open and positively charged ions rush in, creating an electrical spike called an action potential that travels down the axon. Firing is all-or-none: a neuron either fires fully or not at all; stronger stimuli make it fire more often, not more strongly.
Synapses and neurotransmitters
At the synapse, the tiny gap between neurons, the signal becomes chemical. Neurotransmitters released from terminal buttons cross the gap and bind to receptors on the next neuron. Leftover neurotransmitter is cleared away or taken back up, a process called reuptake. Dopamine is linked to reward and movement, serotonin to mood and sleep, and acetylcholine to muscle action and memory.
Flashcard
A nerve cell that transmits information
Check your understanding
A medication blocks the reuptake of serotonin. What is the most direct effect?