The Prototypical Neuron

Soma: Also called the cell body or perikaryon; contains the nucleus and organelles found in other cell types.
Nucleus: The part of the cell that contains deoxyribonucleic acid (DNA), which codes for proteins.
Soma can measure from 5 μm to 100 μm in diameter, depending on the type of neuron.
The nucleus contains deoxyribonucleic acid (DNA), which codes for proteins.

Dendrite: An outgrowth of the neuron at which connections between neurons are typically made.
Resemble tree branches.
They have receptors to which neurotransmitters bind.
Each type of neurotransmitter binds to its own type of receptor.
Dendrites have small outgrowths called dendritic spines, which have neurotransmitter receptors.
This increases the number of connections dendrites can make with other neurons.
They undergo plastic changes in response to experience, which underscores their importance in learning and memory.
Abnormalities in dendritic spines may be related to developmental problems.

Axon: An outgrowth of neurons through which action potentials are conducted.
Joins the soma to the axon terminals.
Axon hillock: The point of contact between the soma and the beginning of the axon.
Action potentials are initiated here.
A bundle of axons in the central nervous system is called a tract.
A bundle of axons in the peripheral nervous system is referred to as a nerve.
Axons can be very long, up to 1.5 m in length or more.
The longest nerve in the human body is the sciatic nerve.
People with sciatica can experience pain down the leg and sometimes all the way down to their toes.

Axon terminal: The part of the axon farthest from the cell body; stores and releases neurotransmitters.
They contain packets of neurotransmitters called synaptic vesicles.
Synaptic cleft: The tiny gap that exists between neurons.
Ligand: Neurotransmitters or other chemicals, such as drugs, that bind to neurotransmitter receptors.
Ligand-gated ion channels: Channels that open in response to the binding of ligands to their receptors.
Synapse: The point at which neurons communicate.
Presynaptic neuron: The neuron that releases neurotransmitter molecules into the synaptic cleft.
Postsynaptic neuron: The neuron located across the synaptic cleft.