The Neuron

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cell body

The metabolic center of the neuron. Also called the soma.

cell membrane

A semipermeable membrane that encloses the neuron.

axon

A long, narrow extension that projects from the cell body. Carries messages to cell body from terminal buttons.

axon hillock

The cone-shaped region at the junction between the axon and cell body. Cell summates messages and sends them to the cell body.

myelin sheath

Fatty insulation surrounding the axon. Enables action potentials to be communicated more quickly. 80% fat molecules, 20% protein.

nodes of ranvier

Gaps between sections of myelin. Critical to the increased speed of induction messages.

dendrite

A short extension emanating from the cell body that receives contacts from other neurons. First pont of contact with other cells. Summated only by the axon hillock.

terminal buttons

Button-like endings on axon branches that contain chemicals for communication between cells (i.e., neurotransmitters).

nucleus

The spherical DNA-containing structure of the cell body. Contains chromosomes which produce our genes.

cytoplasm

The clear internal fluid of a cell.

mitochondria

Sites of energy production and release.

endoplasmic reticulum

A system of folded membranes; Rough portions are involved in protein synthesis. Smooth portions are involved in fat synthesis.

ribosomes

Located on rough endoplasmic reticulum. Cellular structures on which proteins are synthesized.

golgi complex

A system of membranes that packages molecules in vesicles.

microtubules

Tubules that allow for the rapid transport of material throughout neurons.

synaptic vesicles

Spherical membrane packages that store neurotransmitter molecules ready for release from the terminal button.

neurotransmitters

Molecules that are released from the terminal buttons of active neurons and influence the activity of other cells.

unipolar neurons

Have one projection extending from the cell body.

bipolar neurons

Have two projections extending from the cell body.

multipolar neurons

Have more than two projections extending from the cell body (e.g., one axon and many dendrites). The most common type of neuron found in the CNS.

glial cells

Found throughout the nervous system, more common than neurons. Surround and support neurons, control the supply of nutrients to neurons, assist in the exchange of chemicals between neurons, destroy and remove neurons damaged by disease and injury. four types have been identified. Ratio of 10:1 to neurons

oligodendrocytes

Produce the myelin sheaths that surround the axons of neurons of the CNS. Extensions from a single cell wrap around the axons of multiple neurons.

schwann cells

Produce the myelin sheaths that surround the axons of neurons of the PNS. Multiple cells wrap around the axon of a single neuron.

microglia

The smallest glial cells. Trigger inflammatory responses to brain damage and remove injured or dead neurons.

astrocytes

The largest glial cells. Hold neurons in place, provide nutrients (e.g., lactate) to neurons, limit the "dispersion" of neurotransmitters released by terminal buttons, and remove injured or dead neurons. Phagocytosis - consume injured or dead cells named this way because of their star shape. Provide nutrients to neurons, surround the synapses and constrain chemical communication between the cells. Break down glucose (from blood in our vessels) into lactate which can be taken up by neurons immediately

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