Biology of the Brain: Neurons and Neurotransmission

Vocabulary flashcards covering neurons, synapses, neurotransmitters, and related processes discussed in the biology of the brain lecture.

Neuron

The basic structural and functional unit of the nervous system; ~85 billion in the human brain; transmits electrical impulses and chemical signals.

Dendrite

Branch-like extensions of a neuron that receive signals from other neurons via neurotransmitters.

Soma (cell body)

The central part of a neuron that integrates inputs and contains the nucleus with DNA.

Nucleus

The organelle in the cell body that contains the cell’s genetic material (DNA).

Axon hillock

The region where inputs are integrated and an action potential is initiated if the threshold is reached.

Axon

The long projection that conducts electrical impulses away from the soma toward other neurons or effector cells; may be insulated by myelin.

Myelin

The insulating sheath around axons that speeds signal transmission and protects the signal from degradation.

Action potential

An all-or-nothing electrical impulse that travels down the axon when threshold is reached, triggering neurotransmitter release.

Threshold

The level of stimulation required to trigger an action potential.

All-or-nothing

Principle that a neuron fires completely or not at all; no partial firing.

Refractory period

The brief time after firing when a neuron cannot fire again, allowing recovery.

Synapse

The junction between two neurons where chemical signals are passed via neurotransmitters; includes presynaptic and postsynaptic elements, separated by a synaptic cleft.

Synaptic cleft

The tiny gap (<40 nanometers) between presynaptic and postsynaptic membranes through which neurotransmitters travel.

Presynaptic neuron

The neuron that releases neurotransmitters into the synaptic cleft upon an action potential.

Postsynaptic neuron

The neuron that receives neurotransmitters and may fire an action potential.

Vesicle

A small sac in the presynaptic terminal that stores neurotransmitters and releases them when triggered.

Neurotransmitter

Chemical messengers released by the presynaptic neuron that bind to receptors on the postsynaptic neuron; examples include dopamine, serotonin, norepinephrine, adrenaline.

Receptor

Proteins on the postsynaptic membrane that bind neurotransmitters and initiate a response.

Diffusion

The passive spreading of neurotransmitter molecules away from the synaptic cleft after release.

Reuptake

The process by which neurotransmitters are taken back into the presynaptic neuron for reuse.

Enzymatic degradation

The breakdown of neurotransmitters in the synaptic cleft by enzymes.

Recycling

Reuse of neurotransmitter components to synthesize new molecules.

Dopamine

A neurotransmitter involved in reward reinforcement; dysregulation linked to ADHD, schizophrenia, and Parkinson’s disease.

Serotonin

A mood-related neurotransmitter; linked to depression and targeted by SSRIs to increase availability.

Norepinephrine (noradrenaline)

A neurotransmitter involved in attention/concentration and the body’s fight-or-flight response.

Adrenaline (epinephrine)

A hormone/neurotransmitter associated with arousal and the fight-or-flight response.

SSRIs (Selective Serotonin Reuptake Inhibitors)

A class of antidepressants that block the reuptake of serotonin, increasing its availability in the synaptic cleft.

Excitatory vs Inhibitory

Neurotransmitters that increase (excitatory) or decrease (inhibitory) the likelihood that the postsynaptic neuron will fire.

Synaptic transmission

The process by which an action potential prompts neurotransmitter release, diffusion across the cleft, receptor binding, and a postsynaptic response.

EEG

A technique to measure the brain’s electrical activity by recording collective neural firing.