The master control system that regulates and coordinates life functions. It works by monitoring internal and external stimuli and responding via rapid electrical impulses transmitted throughout the body.

The processing command center of the body. It consists structurally of the brain and spinal cord. It integrates sensory information and coordinates motor responses.

The network of nerves located outside the CNS. It connects the brain and spinal cord to the rest of the body (limbs, organs, and skin).

Organs that carry out the actual response to a nervous impulse. The two primary types of effectors are muscles (which contract) and glands (which secrete hormones or substances).

A specialized nerve cell designed to transmit electrical impulses (messages). While they vary in shape, most share three common structures: dendrites, a cell body, and an axon.

Branch-like extensions that receive chemical signals or stimuli from other neurons or the environment and conduct electrical currents toward the cell body.

The metabolic center of the neuron containing the nucleus and organelles. It functions as the cell’s life-support center and integrates incoming signals from dendrites.

A long, singular extension that carries electrical impulses (action potentials) away from the cell body toward other neurons, muscles, or glands.

A fatty, insulating layer that covers the axons of some neurons. It significantly speeds up the transmission of neural impulses.

The cone-shaped region where the axon joins the cell body. This is often the “trigger zone” where the decision to fire an action potential is made.

The branched endpoints of an axon. They contain synaptic vesicles filled with neurotransmitters, which are released to communicate with the next cell.

Neurons that carry information from receptors (detecting pain, temperature, touch) toward the CNS. They allow the body to detect changes in the external or internal environment.

Neurons located entirely within the CNS, positioned between sensory and motor pathways. They account for 90% of all neurons and are responsible for processing, storing, and retrieving information.

Neurons that carry command signals away from the CNS to effectors (muscles and glands) to execute a response.

Also known as a neural impulse. It is a rapid, temporary electrical signal that travels down the axon caused by the movement of ions (like Na+ and K+) across the membrane.

The electrical charge difference across the neuronal membrane when the neuron is not firing. It is approximately -70 mV (inside is negative relative to the outside).

Information strictly flows in one direction within a neuron:
Dendrites → Cell Body → Axon → Axon Terminals.

The synapse is the junction between two neurons (presynaptic and postsynaptic). The synaptic cleft is the physical gap between them where the electrical signal must be converted into a chemical signal to cross.

Channels located in the axon terminal membrane. When the action potential arrives, these channels open, allowing Calcium (Ca²⁺) to rush into the cell. This calcium influx triggers the release of neurotransmitters.

The active transport mechanism where synaptic vesicles fuse with the presynaptic membrane, releasing their neurotransmitters into the synaptic cleft.

Neurotransmitters are chemical messengers that diffuse across the cleft. They bind to specific Ligand-gated channels on the postsynaptic membrane, causing those channels to open (e.g., allowing Na+ to enter) and passing the signal to the next cell.