Neurons, Nerves, and Glial Cells

Neuron

An individual nerve cell.

Neuron

A microscopic structure that carries nervous impulses in a specific direction.

Dendrites

Branching fibers that receive stimuli and begin the nervous impulse.

Cell body

Receives impulses from dendrites and contains the nucleus.

Nucleus

Located inside the cell body.

Ganglia

Small collections of nerve cell bodies outside the brain and spinal cord.

Ganglion

Singular form of ganglia.

Axon

Extends from the cell body and carries impulses away from it.

Myelin sheath

Fatty covering around axons that insulates and speeds impulse transmission.

Demyelination

Loss of the myelin sheath.

Multiple sclerosis (MS)

Disease characterized by demyelination affecting the CNS.

Synapse

Space between neurons where neurotransmitters are released.

Neurotransmitters

Chemical messengers released into the synapse.

Neurotransmitters examples

Examples include acetylcholine, norepinephrine, epinephrine, dopamine, serotonin, and endorphins.

Vesicles

Tiny sacs at the ends of neurons that store neurotransmitters.

Receptors

Located on dendrites and pick up neurotransmitters.

Inactivators

End the activity of neurotransmitters after they finish working.

Neuron

Microscopic individual nerve cell.

Nerve

Macroscopic bundle of many axons traveling together like strands of rope.

Afferent (sensory) nerves

Carry impulses toward the brain and spinal cord.

Afferent nerves

Receive signals from the skin, eyes, ears, and nose.

Efferent (motor) nerves

Carry impulses away from the CNS.

Efferent nerves

Send messages to muscles, glands, and organs.

Parenchyma

Essential functional tissue of an organ.

Nervous system parenchyma

Neurons and nerves that conduct electrical impulses.

Stroma

Connective and supportive tissue of an organ.

Glial (neuroglial) cells

Supportive tissue cells of the CNS.

Glial cell functions

Functions include supporting neurons, forming framework, and fighting infection.

Glial cells

Do not transmit impulses, are more numerous than neurons, and can reproduce.

Types of glial cells

Four types include astrocytes, microglia, oligodendroglia, and ependymal cells.

Astrocytes

Star-like glial cells associated with blood vessels.

Astr/o

Combining form meaning star.

Astrocyte function

Transport water and salts between capillaries and neurons.

Astrocytes

Important part of the blood-brain barrier.

Microglial cells

Small glial cells that act as phagocytes.

Microglial cell function

Protect neurons during inflammation and remove waste.

Oligodendroglial cells

Also called oligodendrocytes.

Olig/o

Combining form meaning scanty or few.

Oligodendroglial cell function

Form the myelin sheath around axons.

Ependymal cells

Line membranes within the brain and spinal cord.

Ependymal cells

Areas where CSF is produced and circulates.

Glial (neuroglial) cells

Supportive, protective, and connective tissue cells of the CNS.

Stromal tissue

Glial cells are the framework tissue of the CNS.

Neurons

Carry nervous impulses.

Blood-brain barrier (BBB)

Protective barrier between blood and brain cells.

BBB function

Prevents harmful substances from entering brain tissue.

BBB structure

Made of endothelial cells and astrocytes.

BBB importance

Separates capillaries from nerve cells.

BBB clinical importance

Makes delivery of chemotherapy drugs to brain tumors difficult.