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Neurotransmitter chemical released at the ends of nerve cells.

Afferent nerves

Carry nervous impulses toward the brain and spinal cord; sensory nerves.


Pertaining to loss or absence of voluntary movement.


Absence of sensitivity to pain.


Congenital condition of partial or complete absence of brain matter.


Lack of feeling or sensation.


Inability to speak; language function is impaired due to injury to the cerebral cortex.


Inability to perform purposeful acts or manipulate objects.

Arachnoid membrane

Middle layer of the meninges that surround the brain and spinal cord.


Glial (neuroglial) cell that transports salts and water from capillaries.


Without coordination.

Autonomic nervous system

Nerves that control involuntary body functions of muscles, glands, and internal organs.


Microscopic fiber that carries a nervous impulse along a nerve cell.

Blood-brain barrier

Blood vessels that let certain substances enter the brain tissue and keep other substances out.


Slow movement.


Lower portion of the brain that connects the cerebrum with the spinal cord.

Cauda equina

Collection of spinal nerves below the end of the spinal cord.


Intensely unpleasant burning pain in a limb following damage to nerves.

Cell body

Part of the nerve cell (neuron) that contains the nucleus.

Central nervous system

Brain and spinal cord.


Head pain; headache.


Pertaining to the cerebellum.


Pertaining to the cerebellum and pons.


Part of the brain that coordinates muscle movements and maintains balance.

Cerebral cortex

Outer region of the cerebrum.

Cerebrospinal fluid

Clear, watery fluid that circulates throughout the brain and spinal cord.


Largest part of the brain; responsible for voluntary muscular activity, vision, speech, taste, hearing, thought and memory, among other functions.


State of unconsciousness from which a patient cannot be aroused.


Pertaining to a coma.

Cranial nerves

Twelve pairs of nerves that carry messages to and from the brain.


Microscopic branching portion of a nerve cell; first part of the nerve cell to receive the nervous impulse.

Dura mater

Thick, outermost layer of the meninges surrounding the brain and spinal cord.


Impairment of the ability to perform voluntary movements.


Difficulty in reading, writing, and learning.

Efferent nerves

Carry messages away from the brain the spinal cord; motor nerves.


Inflammation of the brain.


Disease of the brain.

Ependymal cell

A glial cell that lines the membranes within the brain and spinal cord and helps form cerebrospinal fluid.

Epidural hematoma

Collection of blood located above the dura mater.


Collection of nerve cell bodies in the peripheral nervous system; plural is ganglia.

Glial cell

Nervous system cell that is supportive and connective in function: Astrocyte, microglial cell, ependymal cell.


Rapidly growing malignant tumor of the brain.


Sheet of nerve cells that produces a rounded fold on the surface of the cerebrum.


Slight paralysis of the right or left half of the body.


Paralysis of the right or left half of the body.


Diminished sensitivity to pain.


Excessive sensitivity or feeling, especially of the skin in response to touch or pain.


Excessive movement.


Portion of the brain beneath the thalamus; controls sleep, appetite, body temperature, and secretions from the pituitary gland.


Pertaining to within the membranes (meninges) surrounding the brain and spinal cord.


Inflammation of the two thinner membranes (arachnoid and pia mater) surrounding the brain and spinal cord.

Medulla oblongata

Lower part of the brain, closest to the spinal cord; controls breathing heartbeat, and size of blood vessels.


Pertaining to the meninges.


Three membranes surrounding and protecting the brain and spinal cord.


Tumor (benign) of the meninges.

Microglial cell

Phagocytic glial cell that removes waste products from the central nervous system.


A severe headache, often unilateral, and sometimes accompanied by nausea and vomiting.

Motor nerves

Carry impulses from the brain and spinal cord to muscles.

Myelin sheath

Fatty, white covering over the axon of a nerve cell.


X-ray record (with contrast) of the spinal cord.


Congenital hernia (protrusion) of the spinal cord and meninges through a defect (gap) in the vertebral column. This defect is often associated with spina bifida.


Pertaining to muscle and nerve.


Sudden seizures of sleep.


Macroscopic cordlike collection of fibers that carry electrical impulses.


Nerve pain.


Lack of strength in nerves; a feeling of weakness and exhaustion.


Supporting cells (stroma) of the nervous system; glial cells.


Nerve cell.


Disease of nerves; primarily in the peripheral nervous system.


Chemical messenger released at the end of a nerve cell.

Oligodendroglial cell

Glial (neuroglial) cell that forms the myelin sheath covering the axon of a neuron.


Paralysis of the lower part of the body and both legs.

Parasympathetic nerves

Involuntary, autonomic nerves that regulate normal body functions, such as heart rate, breathing, and the muscles of the gastrointestinal tract.


Essential, functioning cells of any organ. Neurons (nerve cells) are the parenchyma of the nervous system.


Slight paralysis.


Abnormal nervous sensation occurring without apparent cause. Examples are tingling, numbness or prickling sensations.

Peripheral nervous system

Nerves outside the brain and spinal cord; cranial, spinal, and autonomic nerves.

Pia mater

Thin, delicate, innermost membrane of the meninges.


Network of nerves outside of the central nervous system; brachial, cervical, lumbosacral plexuses are examples.


Inflammation of the gray matter of the spinal cord.


Inflammation of many nerves.


Part of the brainstem anterior to the cerebellum, between the medulla and the rest of the brain. The pons connects the upper and lower portions of the brain.


Paralysis of all four limbs; both arms and both legs.


Inflammation of a spinal nerve root.


Disease of a spinal nerve root.


Organ that receives nervous stimulation and passes it on to nerves that carry the stimulation to the brain and spinal cord; skin, ears, eyes and taste buds.

Sciatic nerve

Extends from the base of the spine down the thigh, lower leg, and foot. Sciatica is pain along the course of the nerve.

Sensory nerves

Carry messages to the brain and spinal cord from a receptor; afferent nerves.

Spinal nerves

Thirty-one pairs of nerves arising from the spinal cord. Each spinal nerve affects a particular area of the skin.


Agent of change (light, sound, touch) that evokes a response.


Connective and supportive tissue of an organ.

Subdural hematoma

Collection of blood in the space below the dura mater surrounding the brain.


Depression or groove in the surface of the cerebral cortex; fissure.

Sympathetic nerves

Autonomic nerves that activate responses in times of stress; heartbeat, respiration, and blood pressure are affected.


Space between nerve cells or between nerve cells and muscle and glandular cells.


Pertaining to syncope (fainting).


Fainting; temporary loss of consciousness.


Pertaining to the thalamus.


Main relay center of the brain; located in the central region or diencephalon of the brain.

Trigeminal neuralgia

Flashes of stab like pain along the course of a branch of the trigeminal nerve (5th cranial nerve). The trigeminal nerve has branches to the eye, upper jaw and lower jaw.


Pertaining to the vagus nerve.

Vagus nerve

Tenth cranial nerve with branches to the chest and abdominal organs.

Ventricles of the brain

Fluid (cerebrospinal fluid) filled canals in the brain.

Absence seizure

Minor form of seizure, consisting of momentary clouding of consciousness and loss of contact with the environment.

Alzheimer disease

Brain disorder marked by progressive, gradual mental deterioration (dementia) along with personality changes and impairment of daily functioning.

Amyotropic lateral sclerosis

Degenerative disorder of motor neurons in the spinal cord and brainstem and resulting in total body paralysis.


Weakening of an arterial wall, which may lead to hemorrhage and cerebrovascular accident (stroke).


Brain tumor composed of astrocytes (glial cells). The most serious of these tumors is a glioblastoma multiforme (Grades III and IV malignant brain tumor).


Peculiar sensation appearing before more definite symptoms.

Bell palsy

Unilateral paralysis of the face caused by a disorder of the facial nerve.

Cerebral angiography

X-ray record of blood vessels in the brain after intravenous injection of contrast material.

Cerebral concussion

Temporary brain dysfunction (brief loss of consciousness) after injury; usually clearing within 24 hours.

Cerebral contusion

Bruising of brain tissue as a result of direct trauma to the head; neurologic disorder persists longer than 24 hours.

Cerebral hemorrhage

Bursting of an artery in the brain.

Cerebral palsy

Partial paralysis and muscular coordination caused by loss of oxygen or blood flow to the cerebrum during pregnancy or in the perinatal period.

Cerebrospinal fluid analysis

Samples of cerebrospinal fluid are examined for blood cells, protein, glucose, tumor cells, bacteria and other substances.

Cerebrovascular accident (CVA)

Disruption of the normal blood supply to the brain; stroke.

Computed tomography

Cross-sectional x-ray imaging of an organ (such as the brain or spinal cord), with or without contrast material.


Mental decline and deterioration.


Destruction of myelin on axons of nerves (as in multiple sclerosis).


Neurotransmitter in the central nervous system; deficient in patients with Parkinson disease.

Doppler/ultrasound studies

Sound waves are used to detect blood flow in arteries within the brain and leading to the brain.

Electroencephalography (EEG)

Process of recording the electricity within the brain.


Blood clot that is carried by the bloodstream from one area of the body to another where it blocks a blood vessel.


Brain disorder marked by recurrent attacks (seizures) of abnormal nervous impulses.


Manner of walking.

Glioblastoma multiforme

Highly malignant brain tumor composed of glial cells (astrocytes).

Herpes zoster

Viral infection affecting peripheral nerves.

HIV encephalopathy

Disease of the brain (dementia) caused by infection with the human immunodeficiency virus (HIV), which causes AIDS (acquired immunodeficiency syndrome).

Huntington disease

Hereditary disorder affecting the cerebrum and involving abrupt, involuntary, jerking movements and mental deterioration in later stages.


Abnormal accumulation of cerebrospinal fluid in the ventricles (canals) of the brain.

Ictal event

Pertaining to a sudden, acute onset, as the convulsion of an epileptic seizure.


The two thinner membranes—the pia mater and the arachnoid membrane—surrounding the brain and spinal cord.

Lumbar puncture

Withdrawal of cerebrospinal fluid from the subarachnoid space between two lumbar vertebrae; spinal tap.

Magnetic resonance imaging

Magnetic and radio waves create an image of an organ three planes of the body. The brain and spinal cord can be imaged to detect lesions.


Inflammation of the meninges.


Hernia of the meninges through a defect or space between vertebrae; a form of spina bifida cystica.


A severe headache that is often accompanied by nausea and vomiting.

Multiple sclerosis

Chronic neurologic disorder marked by destruction of the myelin sheath on neuronal axons in the CNS and replacement by plaques of sclerotic tissue.

Myasthenia gravis

Autoimmune neuromuscular disorder characterized by weakness of voluntary muscles.


Blockage or obstruction.


Relieving symptoms, but not curative.



Parkinson disease

Degeneration of nerve cells that produce the neurotransmitter, dopamine in the brain; leads to tremors, weakness of muscles, and slowness of movement.

Positron emission tomography

Computerized radiologic procedure using radioactive glucose or oxygen to image the metabolic activity of cells, such as brain cells.


Viral (herpes zoster) illness that affects peripheral nerves; produces blisters and pain on the skin overlying the path of peripheral nerves.

Spina bifida

Congenital defect in the lumbar spinal column caused by imperfect union of vertebral parts; spinal cord and meninges may herniate through the vertebral gap.

Stereotactic radiosurgery

Use of a specialized instrument using three-dimensional coordinates to locate the site to be operated on.


Abnormal condition of clot formation in a blood vessel.

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