Protein in the cell membrane that actively transports a substance across the membrane.

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 intellectual disability, physical changes, and death by about age 5.

Glial cells that originate in the blood, aid in cell repair, and scavenge debris in the nervous system.

Association cell interposed between a sensory neuron and a motor neuron; in mammals, interneurons constitute most of the brain’s neurons.

Glial cell in the PNS that myelinates sensory and motor axons.

Glial cell that makes and secretes CSF; found on the walls of the brain’s ventricles.

Alteration of an allele that yields a different version of its protein.

Sensory neuron with one axon and one dendrite.

Spatial junction between one neuron and another; forms the information transfer site between neurons.

Folded-up polypeptide chain that serves a particular function in the body.

Distinctively shaped interneuron found in the cerebellum.

Typical allele (most common in a population).

Cell that detects or carries sensory information into the spinal cord and brain.

Protrusion that greatly increases the dendrite’s surface area; typical point of dendritic contact with the axons of other cells.

Comprehensive map of all structural connectivity (the physical wiring) in an organism’s nervous system.

Buildup of fluid pressure in the brain and, in infants, swelling of the head, if the flow of CSF is blocked; can result in intellectual impairment.

Having two identical alleles for a trait.

Juncture of soma and axon.

Loss of sensation and movement due to nervous system injury.

Root, or single fiber, of a neuron that carries messages to other neurons.

Chromosomal abnormality resulting in intellectual impairment and other abnormalities, usually caused by an extra chromosome 21.

Mass of new tissue that grows uncontrolled and independent of surrounding structures.

Product of technology in which one or more genes from one species is introduced into the genome of another species to be passed along and expressed in subsequent generations.

Having two different alleles for the same trait.

Glial cells in the CNS that myelinate axons.

Branching extension of a neuron’s cell membrane; greatly increases the cell’s surface area; collects information from other cells.

Brain cell that brings sensory information from the body into the spinal cord.

Functional group of neurons that connects wide areas of the brain and spinal cord.

Nervous system cell that provides insulation, nutrients, and support and that aids in repairing neurons and eliminating waste products.

Distinctively shaped interneuron found in the cerebral cortex.

Branch of an axon.

Epigenetic process in which a methyl group attaches to the DNA sequence, suppressing or enabling gene expression.

Alternative form of a gene; a gene pair contains two alleles.

Glial coating that surrounds axons in the central and peripheral nervous systems; prevents adjacent neurons from short-circuiting.

DNA segment that encodes the synthesis of a particular protein.

Opening in a protein embedded in the cell membrane that allows the passage of ions.

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.

Protein embedded in a cell membrane that allows substances to pass through the membrane on some occasions but not on others.

Knob at the tip of an axon that conveys information to other neurons.

Star-shaped glial cell that provides structural support to CNS neurons and transports substances between neurons and blood vessels.

Hereditary disease characterized by chorea (ceaseless involuntary jerky movements) and progressive dementia, ending in death.

Core region of the cell containing the nucleus and other organelles for making proteins.

Cell that carries efferent information from the brain and spinal cord to make muscles contract.