Neurons and Neural Firing

Neuron

A specialized cell that receives, processes, and transmits information.

Dendrites

Branch-like extensions that receive signals from other neurons.

Cell Body (Soma)

The part of a neuron that contains the nucleus and integrates incoming signals.

Nucleus

The cell structure that contains genetic material and helps control the cell’s activities.

Axon

The long extension of a neuron that carries electrical impulses away from the cell body.

Myelin Sheath

A fatty insulating layer around some axons that speeds up neural transmission.

Glial Cells

Cells that support, protect, and maintain neurons; some produce myelin.

Terminal Buttons

The ends of axons that release neurotransmitters into the synapse.

Synapse

The junction between neurons where communication occurs.

Neurotransmitters

Chemical messengers released by neurons that transmit signals across a synapse.

Receptors

Structures on a cell that bind to specific chemical messengers.

Resting Potential

The electrical charge difference across a neuron’s membrane when it is not firing an action potential.

Threshold

The level of stimulation needed to trigger an action potential.

Action Potential

A brief electrical impulse that travels down a neuron’s axon.

All-or-None Principle

The principle that an action potential either occurs fully or does not occur at all.

Depolarization

The phase of an action potential when the neuron’s membrane becomes less negative, mainly because sodium ions enter.

Repolarization

The phase when the membrane returns toward its resting electrical state, mainly as potassium ions leave.

Reuptake

The process by which a sending neuron takes neurotransmitters back up after they have been released.

Agonist

A substance that increases or mimics a neurotransmitter’s effects.

Antagonist

A substance that blocks or reduces a neurotransmitter’s effects.

Reuptake Inhibitor

A substance that blocks neurotransmitter reabsorption, leaving more available in the synapse.

Multiple Sclerosis (MS)

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

Dopamine

A neurotransmitter involved in movement, motivation, reward, and learning.

Serotonin

A neurotransmitter involved in mood, sleep, and other functions.

Norepinephrine

A neurotransmitter involved in alertness, attention, and arousal.

GABA

The primary inhibitory neurotransmitter in the brain; it reduces the likelihood that neurons will fire.

Glutamate

The primary excitatory neurotransmitter in the brain; it supports learning and memory.

Acetylcholine (ACh)

A neurotransmitter involved in muscle movement, attention, learning, and memory.

Endorphins

Chemicals produced by the body that help reduce pain and can contribute to feelings of well-being.

Substance P

A chemical messenger involved in transmitting pain signals.

Sympathetic Nervous System

The division of the autonomic nervous system that prepares the body for action during stress.

Parasympathetic Nervous System

The division of the autonomic nervous system that supports rest, digestion, and recovery.

Reflex Arc

A neural pathway that produces a rapid, automatic response to a stimulus.