GLOSSARY OF MEDICAL TERMS
Acute:
Term used to describe the critical early stage after an injury.
Antibody:
Produced by the immune system to protect the body from infection, antibodies can also be generated in laboratories for specific purposes: e.g. when antibodies interact with the inhibitory molecule Nogo, they inactivate it and allow the growth of axons.
Ascending sensory pathways:
Transmit sensory information up the spinal cord from the skin, muscles and internal organs. These pathways convey information about, for example, pain, temperature, touch, vibration and pressure.
Astrocytes:
A type of glial cell that provides physical support for neurons in the brain and spinal cord.
Autonomic dysreflexia:
Exaggerated autonomic reflexes manifested by raised blood pressure, severe headache and sweating above the spinal cord lesion. Common with injuries above T6 and caused by, for example, an overfull bladder.
Autonomic nervous system:
The nervous system responsible for management of non-conscious functions such as heartbeat, controlling blood flow, the digestive system and sweating.
Axon:
Part of the neuron that extends from the cell body. Signals are carried down the axon from the cell body to the nerve endings that transmit the signal to other neurons or muscles.
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Cell body:
The main bulk of the neuron where the nucleus is found, containing the cell's DNA.
Central nervous system:
Neurons and glia of the brain and spinal cord.
Cervical region:
Contains the eight vertebrae (C1-C8) that are closest to the skull. Injury here has the most widespread consequences including loss of function in the hands and arms.
Chronic:
A term used to describe a long-term stable medical condition.
Chondroitinase:
An enzyme derived from bacteria that is able to break down components of the extracellular matrix and allow growth of regenerating axons.
Clinical trial:
Testing therapies in human patients to ensure that treatments are safe and do not worsen the existing injury.
Complete injury:
Damage across the whole of the width of the spinal cord. This results in no function (either sensation or muscle control) below level of injury.
Corticospinal tract:
Pathways of axons within the spinal cord that relay signals from neurons in the brain that control muscle activity.
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Demyelination:
Removal of the insulating and protective layer from axons, reducing their ability to conduct signals properly. This could be due to death or damage to the oligodendrocytes or Schwann cells in a traumatic injury, or the result of a demyelinating disease.
Dendrites:
Branch-like structures of neurons that form contacts with and detect signals from other neurons.
Descending motor pathways:
Transmit messages from the brain, down the spinal cord to other parts of the body. They control the activity of muscles and regulate blood pressure, temperature and the body's circulatory response to stress.
Dorsal root:
Bundles of nerve fibres as they enter the spinal cord, carrying sensory information. The cell bodies of the sensory neurons lie in the dorsal root ganglion, a swelling of the dorsal root just outside the spinal cord.
Dysfunction:
Impaired control of movement or perception of sensations due to partial spinal cord damage.
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Electrophysiology:
measurement of electrical signals in the nervous system such as those which stimulate muscle activity.
Ephrins:
A group of inhibitory molecules that block axon growth.
Extracellular matrix:
A complex mixture of molecules secreted by cells that provides an important structural and biochemical coating. Unfortunately it is also a barrier to regrowing axons.
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Fibroblast:
Spindle-shaped cells that provide important structural properties in many tissues. They are very useful for genetic manipulation e.g. to produce growth factors.
Fibronectin:
A component of the structural material that surrounds cells (the extracellular matrix). Although important in normal conditions, it becomes a barrier to regrowing axons.
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Glial cells:
The supporting cells of the nervous system that enable neurons to function correctly. There are four main types of glial cells in humans and other mammals. Astrocytes, microglia and oligodendrocytes occur in the brain and spinal cord. Schwann cells are found only in peripheral nerves (nerves other than those in the brain and spinal cord).
Grey matter:
The grey, butterfly-shaped centre of the spinal cord that contains the cell bodies of neurons in the spinal cord.
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In vitro:
Laboratory research carried out in test-tubes, petrie dishes, etc.
In vivo:
Research carried out in living organisms.
Incomplete injury:
An injury that does not spread across the whole of the spinal cord. People with incomplete injuries have some sensation and/or movement control below the level of injury.
Inflammation:
The localised response of a tissue to injury, involving a complex series of interactions including altered blood flow and cells of the immune system. Still poorly understood in the brain and spinal cord.
Interneurons:
Generally small neurons in the spinal cord that contact other neurons and form part of a network of connections.
Intraspinal:
Referring to connections that lie within the spinal cord, e.g. between neurons of adjacent segments.
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Lumbar region:
The lumbar vertebrae (L1-L5) are in the lower back. Injury in this region disrupts voluntary control of leg and hip muscles and affects sensation below the waist.
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Metalloproteinases:
A specific group of enzymes that can break down components of the extracellular matrix, enabling growth of regenerating axons.
Microglia:
Small cells that resemble components of the immune system.
Monoaminergic:
Referring to neurons that transmit signals using a specific group of neurotransmitter molecules.
Motorneurons:
Relatively large neurons, whose axons travel from the spinal cord directly to muscles. They conduct the electrical impulses that stimulate muscles to contract.
Myelin:
The fatty insulating covering that surrounds neurons. This covering is essential for rapid transmission of nerve signals. Produced from oligodendrocytes and Schwann cells.
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Nerve growth factors (also called neurotrophins):
Specialised proteins that interact with the tips of neurons to stimulate growth. They also control the direction of growth.
Neuron:
Specialised cells that transmit nerve impulses quickly and efficiently from one area of the body to another.
Nogo:
A group of protein molecules associated with myelin that are inhibitory to axon growth.
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Olfactory ensheathing glia:
A type of cell that wraps around the axons of nerves that relay the sense of smell from the nose to the brain. They promote axon regeneration when they are transplanted into spinal cord injuries. They also form a new myelin coating around spinal cord neurons.
Oligodendrocytes:
Specialized cells in the brain and spinal cord that wrap around an axon to form a multilayered myelin sheath.
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Paraplegia:
The outcome of injury to the spinal cord resulting in paralysis of the legs and lower body.
Peripheral nervous system:
Neurons and nerve fibres outside of the brain and spinal cord.
Plasticity:
The ability of systems to change, eg. by sprouting new processes, making new synapses or altering the strength of existing synapses.
Propriospinal tract:
Nerve fibre pathways in the spinal cord that relay sensory information to the brain.
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Reflex:
Involuntary reaction to a stimulus.
Regeneration:
The term given to regrowth of damaged tissues, such as the regrowth of damaged axons in the spinal cord.
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Sacral region:
The base of the spinal cord. Injury here affects control and sensation of the legs, genital and anal regions.
Schwann cells:
A type of cell that surrounds and forms the myelin coat around neurons outside of the brain and spinal cord (in the peripheral nervous system). Transplanting Schwann cells into injured spinal cord can stimulate growth of damaged axons and restore myelin.
Sensory function:
The ability to perceive sensory information, such as touch, temperature and pain.
Spasticity:
Uncontrollable muscle contraction.
Spinal levels:
The spinal cord is divided into cervical (closest to the head), thoracic, lumbar and sacral (furthest from the head) levels. Damage to each level results in a characteristic pattern of injury.
Synapse:
A specialized connection between neurons. At synapses, signals pass from one neuron to another using molecules called neurotransmitters.
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Tetraplegia (quadriplegia):
The outcome of injury to the higher regions of the spinal cord, resulting in paralysis of the arms, trunk and legs.
Thoracic region:
The thoracic vertebrae (T1-T12) are in the middle of the back. Injury in this region usually results in paralysis of the muscles in the chest, abdomen and below, together with loss of sensory perception.
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Ventral root:
Bundles of nerve fibres leaving the spinal cord, mostly carrying signals to the muscles.
Vertebrae:
a series of ring-like bones that protect the spinal cord. Together, the vertebrae make up the spinal column.
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White matter:
White-coloured tissue that forms the outer layer of the spinal cord. It contains the ascending and descending axons of neurons in the spinal cord.
