Glossary of Terms

agonist

a drug capable of combining with a receptor and initiating action.

antagonist

a drug that opposes the effects of another by physiological or chemical action or by a competitive mechanism.

apoptosis

also called programmed cell death. A form of cell death in which a programmed sequence of events leads to the elimination of old, unnecessary, and unhealthy cells.

arrhythmia

an abnormal heart rhythm. The heartbeats may be too slow, too rapid, too irregular, or too early.

astrocyte

a type of glial cell responsible for neurotransmission and neuronal metabolism.

autonomic dysreflexia

a potentially dangerous complication of spinal cord injury in which blood pressure rises to dangerous levels. If not treated, autonomic dysreflexia can lead to stroke and possibly death.

axial traction

the application of a mechanical force to stretch the spine; used to relieve pressure by separating vertebral surfaces and stretching soft tissues.

axon

the long, thin extension of a nerve cell that conducts impulses away from the cell body.

axonal growth cone

dynamic structures present at the tip of developing and regenerating axons that respond to chemical cues for growth and direction.

central pattern generators (CPG)

neural circuits that produce self-sustaining patterns of behavior independent of their sensory input. Researchers have found evidence of a locomotor CPG in the spinal cord that synchronizes muscle activity during alternating stepping of the legs and feet.

cervical

the part of the spine in the neck region.

coccygeal

the part of the spine at the bottom of the spinal column, above the buttocks.

cytokine

a small protein released by immune cells that has a specific effect on the interactions between cells, or communications between cells, or on the behavior of cells. dendrite - a short arm-like protuberance from a neuron. Dendrite is from the Greek for "branched like a tree." disc - shortened terminology for an intervertebral disc, a disc-shaped piece of specialized tissue that separates the bones of the spinal column.

electroejaculation

a technique that uses an electric probe to stimulate ejaculation.

embryonic stem cells

undifferentiated cells from the embryo that have the potential to become a wide variety of specialized cell types.

excitotoxicity

a neurological process that is the result of the release of excessive amounts of the neurotransmitter glutamate.

extracellular matrix

the material found around cells composed of structural proteins, specialized proteins, and proteoglycans.

fetal spinal cord cells

cells used by scientists to derive undifferentiated embryonic stem cells for transplant into the damaged spinal cord.

free radicals

highly reactive chemicals that attack molecules and modify their chemical structure.

functional electrical stimulation (FES)

the therapeutic use of low-level electrical current to stimulate muscle movement and restore useful movements such as standing or stepping; also called functional neuromuscular stimulation.

glia

supportive cells in the brain and spinal cord. Glial cells are the most abundant cell types in the central nervous system. There are three types: astrocytes, oligodendrocytes, and microglia. glutamate - an excitatory neurotransmitter.

growth-inhibiting proteins

protein molecules that inhibit axon regeneration.

guidance molecules

molecules that guide axons to their target. Some guidance molecules attract certain axons while repelling others.

hypothermia

abnormally low body temperature.

interneurons

neurons with axons that remain within the spinal cord.

intubation

the process of putting a tube into a hollow organ or passageway, often into the airway.

ligament

a tough band of connective tissue that connects various structures such as two bones.

lumbar

the part of the spine in the middle back, below the thoracic vertebrae and above the sacral vertebrae.

macrophage

a type of white blood cell that engulfs foreign material. Macrophages are key players in the immune response to foreign invaders such as infectious microorganisms Macrophages also release substances that stimulate other cells of the immune system.

methylprednisolone

a steroid drug used to improve recovery from spinal cord injury.

microglia

glial cells that function as part of the immune system in the brain and spinal cord.

monocyte

a white blood cell that has a single nucleus and can engulf foreign material. Monocytes emigrate from blood into the tissues of the body and evolve into macrophages.

myelin

a structure of cell membranes that forms a sheath around axons, insulating them and speeding conduction of nerve impulses.

myelotomy

a surgical procedure that cuts into the spinal cord.

neural prostheses

prosthetic devices that can respond to signals from the brain.

neurogenic pain

generalized pain that results from nervous system malfunction.

neuromodulation

a series of techniques employing electrical stimulation or the administration of medication by means of devices implanted in the body. These techniques allow the treatment of a range of disorders including certain forms of pain, spasticity, tremor, and urinary problems.

neuron

also known as a nerve cell; the structural and functional unit of the nervous system. A neuron consists of a cell body and its processes: an axon and one or more dendrites.

neurostimulation

the act of stimulating neurons with electrical impulses delivered via electrodes attached to the brain.

neurotransmitter

a chemical released from neurons that transmits an impulse to another neuron, muscle, organ, or other tissue.

neurotrophic factors

proteins responsible for the growth and survival of neurons.

neutrophil

a type of white blood cell that engulfs, kills, and digests microorganisms.

oligodendrocyte

a type of nerve cell in the brain and spinal cord that surrounds and insulates axons.

olfactory ensheathing glia

non-myelinating glial cells that ensheath olfactory axons within both the PNS and CNS portions of the primary olfactory pathway. They are being used in experiments to build bridges between damaged areas of the spinal cord.

paralysis

the inability to control movement of a part of the body.

paraplegia

a condition involving complete paralysis of the legs.

pressure sore (also known as a pressure ulcer or bed sore)

a reddened area or open sore caused by unrelieved pressure on the skin over bony areas such as the hip-bone or tailbone.

quadriplegia

a condition involving complete paralysis of the legs and partial or complete paralysis of the arms.

receptor

a structure on the surface or interior of a cell that selectively receives and binds to a specific substance.

regeneration

repair, regrowth, or restoration of tissues; opposite of degeneration.

rhizotomy

an operation to disconnect specific nerve roots in order to stop severe spasticity.

sacral

refers to the part of the spine in the hip area.

Schwann cell

the cell of the peripheral nervous system that forms the myelin sheath.

spasticity

increased tone in muscles of the arms and legs (due to lesions of the upper motor neurons).

spinal shock

a temporary physiological state that can occur after a spinal cord injury in which all sensory, motor, and sympathetic functions of the nervous system are lost below the level of injury. Spinal shock can lower blood pressure to dangerous levels and cause temporary paralysis.

stem cell

special cells that have the ability to grow into any one of the body's more than 200 cell types. Unlike mature cells, which are permanently committed to their fate, stem cells can both renew themselves and create cells of other tissues.

synapse

a specialized junction between two nerve cells. At the synapse, a neuron releases neurotransmitters that diffuse across the gap and activate receptors situated on the target cell.

T-cell

an immune system cell that produces substances called cytokines, which stimulate the immune response. thoracic - the part of the spine at the upper-back to mid-back level.

vertebrae

the 33 hollow bones that make up the spine.