Nervous-system cell that provides insulation, nutrients, and support and that aids in repairing neurons and eliminating waste products.
Alteration of an allele that yields a different version of the allele.
cell body (soma)
Core region of the cell containing the nucleus and other organelles for making proteins.
Hereditary disease characterized by chorea (ceaseless, involuntary, jerky movements) and progressive dementia, ending in death.
Distinctive interneuron found in the cerebral cortex.
Product of technology in which number of genes or a single gene from one species is introduced into the genome of another species and passed along and expressed in subsequent generations.
Having two identical alleles for a trait.
multiple sclerosis (MS)
Nervous-system disorder that results from the loss of myelin (glial-cell covering) around neurons.
Alternate form of a gene; a gene pair contains two alleles.
Glial cell in the peripheral nervous system that myelinates sensory and motor axons.
Sensory neuron with one axon and one dendrite.
terminal button (end foot)
Knob at the tip of an axon that conveys information to other neurons.
Star-shaped glial cell that provides structural support to neurons in the central nervous system and transports substances between neurons and blood vessels.
Protein in the cell membrane that actively transports a substance across the membrane.
Refers to a normal (most common in a population).
Protein embedded in a cell membrane that allows substances to pass through the membrane on some occasions but not on others.
Tight junctions between the cells that compose blood vessels in the brain, providing a barrier to the entry of an array of substances, including toxins, into the brain.
Juncture of soma and axon where the action potential begins.
Opening in a protein embedded in the cell membrane that allows the passage of ions.
Junction between one neuron and another that forms the information-transfer site between neurons.
Folded-up polypeptide chain.
Neuron that carries incoming information from sensory receptors into the spinal cord and brain.
'Root,' or single fiber, of a neuron that carries messages to other neurons.
Buildup of pressure in the brain and, in infants, swelling of the head caused if the flow of cerebrospinal fluid is blocked; can result in retardation.
Having two different alleles for the same trait.
Association neuron interposed between a sensory neuron and a motor neuron; thus, in mammals, interneurons constitute most of the neurons of the brain.
Mass of new tissue that grows uncontrolled and independent of surrounding structures.
Distinctive interneuron found in the cerebellum.
Inherited birth defect caused by the loss of genes that encode the enzyme necessary for breaking down certain fatty substances; appears 4 to 6 months after birth and results in retardation, physical changes, and death by about age 5.
Branching extension of a neuron's cell membrane that greatly increases the surface area of the cell and collects information from other cells.
Glial cell that makes and secretes cerebrospinal fluid; found on the walls of the ventricles in the brain.
Glial coating that surrounds axons in the central and peripheral nervous systems; prevents adjacent neurons from short-circuiting.
Brain cell that brings sensory information from the body into the spinal cord.
Glial cells that originate in the blood, aid in cell repair, and scavenge debris in the nervous system.
Glial cells in the central nervous system that myelinate axons.
Chromosomal abnormality resulting in mental retardation and other abnormalities, usually caused by an extra chromosome 21.
Protrusion from a dendrite that greatly increases the dendrite's surface area and is the usual point of dendritic contact with the axons of other cells.
Branch of an axon
Loss of sensation and movement due to nervous-system injury.
Neuron that carries information from the brain and spinal cord to make muscles contract.
DNA segment that encodes the synthesis of a particular protein.