Glossary

Apoptosis

Programmed cell death, or "cell suicide"; a form of cell death in which a controlled sequence of events (or programme) leads to the elimination of cells without releasing harmful substances to the surrounding area.

Ascending pathways

Nerve pathways that go upward from the spinal cord toward the brain and carry sensory information from the body.

Astrocytes

The largest and most numerous of the supporting, or glial, cells in the brain and spinal cord. Astrocytes (meaning "star cells" because of their shape) help regulate the chemical environment around cells, respond to injury, and release regulatory substances that influence nerve cells.

Autonomic dysreflexia

A potentially life-threatening increase in blood pressure, sweating, and other autonomic reflexes in reaction to bowel impaction or some other stimulus.

Axon

Long nerve cell fibres that conduct electrical impulses. Axons contact other nerve, muscle, and gland cells by synapses and the release of neurotransmitters that influence those cells.

Central nervous system (CNS)

The brain and spinal cord.

Conduction

The transmission of an electric impulse from the cell body of the neuron to the synapse via the axon.

Contusion

A bruising injury. Spinal cord contusions result in a cavity or hole in the centre of the spinal cord. Myelinated axons typically survive around the perimeter of the spinal cord, and the dura may even remain unaffected by the injury.

Corticospinal tracts

The nerve fibres that carry signals from motor control areas of the brain's cerebral cortex to the spinal cord (also called the pyramidal tract).

Cyst

Fluid-filled cavity that forms where cells have died. The cyst is often surrounded by a glial scar.

Descending pathways

Nerve pathways that conduct nerve impulses from the brain to the spinal cord and thereby allow the brain to control movement of the body below the head.

Excitotoxicity

Excessive release of neurotransmitters causing damage to nerve and glial cells.

Extended re-growth

Re-growth of the cut axons through and below the injury site, ideally having a reconnection with appropriate target cells.

Extra-cellular matrix

Any material produced by cells and secreted into the surrounding medium but usually applied to the non-cellular portion of animal tissues. The supporting structure to which cells adhere.

Free radicals

Highly reactive chemicals that attack molecules crucial for cell function by capturing electrons and thus, modifying chemical structures. Radicals are common by-products of normal chemical reactions occurring in cells. The body has several mechanisms to deactivate free radicals.

Glia

Supporting cells of the nervous system. Glial cells in the brain and spinal cord by far outnumber nerve cells. Not only do they provide physical support, but also respond to injury, regulate the chemical composition surrounding cells, form the myelin insulation of nervous pathways, and help guide neuronal migration during development. The three major types of glial cells in the CNS are astrocytes, oligodendrocytes, and microglia.

Glial scar

Cluster of activated glial cells which forms a physical barrier to axonal growth. The glial cells release or display substances that inhibit axonal growth.

Glutamate

Excitatory neurotransmitter of the brain.

Grey matter

The parts of the brain and spinal cord composed mainly of cell bodies and dendrites. The grey matter of the spinal cord lies in a butterfly-shaped region in the centre of the cord.

Impulse conduction

The capacity of neuronal cells to conduct electrical signals.

Inflammation

A localised inflammatory response that involves a complex series of events elicited by injury or destruction of tissues, which serves to destroy, dilute or wall off (sequester) both the injurious agent and the injured tissue.

Mammals

Warm-blooded vertebrate animals. They are characterised by a covering of hair on the skin and, in the female, milk-producing mammary glands for nourishing the young. Human beings belong to this group.

Metabolism

Organic processes (in a cell or organism) which are necessary for life. They have some immune functions and become activated in response to damage.

Microglia

A type of "resident" immune cell found in the CNS. Microglia are scavengers that engulf dead cells and other debris.

Motor cortex

The surface region of the brain that instructs motor movements.

Myelin

Electrically insulating coating around axons that gives white matter its whitish appearance. Myelin is essential for the speed and reliability of signal transmission along nerve fibres. In the CNS, oligodendrocytes (a type of glial cell) wrap myelin around axons. In the PNS, Schwann cells generate myelin.

Neurofunctional recovery

A recovery of the nervous system that leads to a regaining of motor activity and/or sensation.

Neuron

A nerve cell.

Neuroregeneration

Regeneration is the ability to restore lost or damaged tissues. The term neuroregeneration refers to the regeneration of the nervous system.

Neurotransmitter

Chemicals released by nerve cells at synapses that influence the activity of other cells. Neurotransmitters may excite, inhibit, or otherwise influence the activity of cells.

Oligodendrocytes

a type of glial cell in the brain and spinal cord. Oligodendrocytes wrap axons with myelin which improves the speed and reliability of impulse conduction. These cells also produce substances that inhibit the regeneration of axons in the adult CNS.

Paraplegia

Complete or partial impairment of sensation and motor activity of the lower part of the body (legs).

Peripheral nervous system (PNS)

All the nerves in the body that are outside of the brain and spinal cord (the central nervous system). It carries messages from all over the body to the central nervous system and vice versa.

Pressure sores

An area of skin that has died due to prolonged pressure, cutting off its normal blood supply. The pressure is usually due to long periods of immobility and lack of pressure relief. The sores can be painful and slow to heal.

Respiratory infection

Results in pneumonia perhaps due to malventilation and/or immune suppression.

Secondary damage

Damage that continues in the hours and days following the initial trauma extending the size of the injury.

Spasticity

A state of increased muscular tone in which abnormal stretch reflexes intensify muscle resistance to passive movements.

Spinal cord segments

Divisions of the spinal cord along its length. Each spinal segment sends a pair of motor and sensory nerves to the body. Higher segments control movement and sensation in upper parts of the body while lower segments control lower parts of the body.

Synapse

The functional connecting structure between a nerve cell axon and target cells, which may be other nerve cells, muscle cells, or gland cells. At the synapse the axon releases a chemical neurotransmitter that diffuses across a tiny gap and binds to receptors (molecules on the surface of the target cell) that then change the target cell's behaviour.

Tetraplegia

Complete or partial impairment of sensation and motor activity of both the upper (arms) and the lower (legs) part of the body.

Trophic support

Support of cell growth and survival, achieved by secreted molecules called trophic factors.

Urinary infection

The infection can "spread" and induce infection of the kidney.

Vertebra

One of the bone segments of the spinal column.

Vertebrates

Animals which have a spinal column (composed of vertebrae). This includes mammals, fishes, birds, reptiles and amphibians.

White matter

Areas of the brain and spinal cord that contain mainly nerve fibres rather than nerve cell bodies and dendrites (grey matter). The myelin insulating covering of axons gives the whitish appearance. White matter is located in the outer portion of the spinal cord, and grey matter is in the centre.