Neurons

Sensory Input

Information gathered by sensory receptors about internal and external changes.

Integration

Interpretation of sensory input.

Motor Output

Activation of effector organs (muscles and glands) that produces a response.

Central Nervous System (CNS)

Composed of the brain and spinal cord.

Peripheral Nervous System (PNS)

Consists of the nerves that connect the brain or spinal cord with the body’s muscles, glands, sense organs, and other tissues.

Neuron

The functional unit of the nervous system that generates electrical signals called action potentials or nerve impulses.

Glial Cells

Non-neuronal cells that support neurons but do not generate nerve impulses.

Astrocytes

Glial cells that help regulate extracellular fluid composition in the CNS.

Microglia

Specialized, macrophage-like cells that perform immune functions in the CNS.

Ependymal Cells

Glial cells that line the fluid-filled cavities within the brain and spinal cord.

Oligodendrocytes

Glial cells that form the myelin sheath of CNS axons.

Dendrites

Branches of a neuron that receive information, typically through neurotransmitters.

Axon Hillock

The initial segment of the axon that generates action potentials.

Axon Terminal

The end of each axon branch that releases neurotransmitters.

Anterograde Transport

Movement of materials forward from the cell body toward axon terminals.

Retrograde Transport

Movement of materials backward from axon terminals toward the cell body.

Afferent Neurons

Transmit information into the CNS from peripheral receptors.

Efferent Neurons

Transmit information out of the CNS to effector cells.

Interneurons

Integrate groups of afferent and efferent neurons within the CNS.

Membrane Potential

The voltage difference between the inside and outside of a cell.

Resting Membrane Potential

The potential difference across the plasma membrane of a neuron when it is at rest.

Depolarization

A shift in membrane potential to a less negative value.

Repolarization

The process of returning to resting membrane potential after depolarization.

Hyperpolarization

The potential becoming more negative than the resting membrane potential.

Action Potential

A brief all-or-none depolarization of the membrane, which reverses polarity in neurons.

Graded Potential

A potential change of variable amplitude and duration conducted decrementally without a threshold.

Synaptic Potential

A graded potential change produced in the postsynaptic neuron in response to neurotransmitter release.

Threshold Potential

The membrane potential at which an action potential is initiated.