11. NERVOUS SYSTEM

Acetylcholine: Neurotransmitter chemical released at the ends of nerve cells.

Afferent nerves: Carry messages toward the brain and spinal cord.

Arachnoid membrane: Middle layer of the three membranes that surround the

brain and spinal cord.

Astrocyte: A type of glial cell that transports water and salts from capillaries.

Autonomic nervous system: Nerves that control involuntary body functions of

muscles, glands and internal organs.

Axon: Microscopic fiber that carries the nervous impulse along a nerve cell.

Blood-brain-barrier: Blood vessels that selectively let certain substances enter the

brain tissue and keep other substances out.

Brainstem: Lower portion of the brain that connects the cerebrum with the spinal

cord. The pons and medulla oblongata are part of the brainstem.

Cauda equina: Collection of spinal nerves below the end of spinal cord.

Cell body: Part of a nerve cell that contains the nucleus.

Central nervous system: Brain and the spinal cord.

Cerebellum: Posterior part of the brain that coordinates muscle movements and

maintains balance.

Cerebral cortex: Outer region of the cerebrum; containing sheets of nerve cells;

gray matter of the brain.

Cerebrospinal fluid: Fluid that circulates throughout the brain and spinal cord.

Cerebrum: Largest part of the brain; responsible for voluntary muscular activity,

vision, speech, taste, hearing, thought and memory.

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

Dendrite: Microscopic branching fiber of a nerve cell that is the first part to receive

the nervous impulse.

Dura mater: Thick, outermost layer of the meninges surrounding and protecting the

brain and spinal cord.

Efferent nerves: Carry messages away from the brain and spinal cord.

Ependymal cell: A glial cell that lines membranes within the brain and spinal cord

and helps form cerebrospinal fluid

Ganglion: Collection of nerve cell bodies in the peripheral nervous system.

Glial cell: Cell in the nervous system that is supportive and connective in function.

Examples are astrocytes, microglial cells, ependymal cells and oligodendrocytes.

Gyrus: Sheet of nerve cells that produces a rounded fold on the surface of the

cerebellum.

Hypothalamus: Portion of the brain beneath the thalamus; controls sleep, appetite,

body temperature and secretions from the pituitary gland.

Medulla oblongata: Part of the brain just above the spinal cord; controls breathing,

heartbeat, and the size of blood vessels; nerve fibers cross over here.

Meninges: Three protective membranes that surround the brain and spinal cord.

Microglial cells: They are small cells with many branching processes. As

phagocytes, they protect neurons in response to inflammation.

Motor nerves: Carry messages away from the brain and spinal cord to muscles and

organs.

Myelin sheath: White fatty tissue that surrounds, and insulated the axon of a nerve

cell. Myelin speeds impulse conduction along axons.

Nerve: Macroscopic cordlike collection of fibers that carry electrical impulses.

Neuron: Nerve cell that carries impulses throughout the body.

Neurotransmitter: Chemical messenger, released at the end of a nerve cell. It

stimulates or inhibits another cell, which can be a nerve cell, muscle cell, or gland

cell. Examples of neurotransmitter are acetylcholine, norepinephrine, dopamine and

serotonin.

Oligodendroglial cell: Glial cell that forms the myelin sheath covering axons. Also

called oligodendrocytes.

Parasympathetic nerves: Involuntary, autonomic nerves that regulate normal

body functions such as heart rate, breathing, and muscles of the gastrointestinal

tract.

Parenchyma: Essential, distinguishing tissue of the nervous system; includes the

brain and spinal cord. This is to distinguish it from surrounding tissues such as

meninges.

Peripheral nervous system: Nerves outside the brain and spinal cord; cranial,

spinal and autonomic nerves.

Pia mater: Thin, delicate inner membrane of the meninges.

Plexus: Large, interlacing network of nerves. Examples are Lumbosacral, cervical

and brachial plexuses.

Pons: Part of the brain anterior to the cerebellum and between the medulla and the

rest of the midbrain. It is a bridge connecting various parts of the brain.

Receptor: Organ that receives a nervous stimulation and passes it on to nerves

within the body. The skin, eyes, ears and taste buds are receptors.

Sciatic nerve: Nerve extending from the base of the spine down the thigh, lower

leg, and foot. Sciatica is pain or inflammation along the course of the nerve.

Sensory nerves: Carry messages to the brain and spinal cord from a receptor.

Spinal nerves: Thirty-one pairs of nerves arising from the spinal cord. Each spinal

nerve affects a particular area of the skin.

Stimulus: Agent of change (light, sound, touch) in the internal or external

environment that evokes a response.

Stroma: Connective and supporting tissue of an organ. Glial cells are the stromal

tissue of the brain.

Sulcus: Depression or groove in the surface of the cerebral cortex.

Sympathetic nerves: Autonomic nerves that influence bodily functions involuntarily

in times of stress.

Synapse: Space through which a nervous impulse is transmitted from one neuron to

another or from a neuron to another cell, such as a muscle or gland cell.

Thalamus: Main relay center of the brain. It conducts impulses between the spinal

cord and the cerebrum; incoming sensory messages are relayed through the

thalamus to appropriate centers in the cerebrum.

Vagus nerve: Tenth cranial nerve; its branches reach to the larynx, trachea,

bronchi, lungs, aorta, esophagus and stomach.

Ventricles of the brain: Canals in the brain that contain cerebrospinal fluid.

Nervous impulse: Energy when released and passed through the length of the

nerve cell.

Astrocytes: They are star-like and transport water and salts between capillaries and

neurons.

Lumbar puncture: Spinal fluid can be withdrawn for diagnosis or relief of pressure

on the brain. A hollow needle is inserted in the lumbar region of the spinal column

below the region where the nervous tissue of the spinal cords ends and CSF is

withdrawn.

Respiratory center: It controls muscles of respiration in response to chemicals or

other stimuli.

Cardiac center: It slows the heart rate when the heart is beating too rapidly.

Vasomotor center: It affects the muscles in the walls of blood vessels, thus

influencing blood pressure.

Spinal cord: It is a column of nervous tissue extending from the medulla oblongata

to the second lumbar vertebra within the vertebral column.

Hematoma: Hematomas are not tumors of blood, but are collections of blood.

Anencephaly: This is a congenital brain malformation; it is not compatible with life

and may be detected with amniocentesis or ultrasonography of the fetus

Glioblastoma: This is a highly malignant tumor. Gliomas are tumors of glial cells.

Leptomeninges: The pia and arachnoid membranes are known as the

Leptomeninges because of their thin, delicate structure.

Myelomeningocele: Neural tube defect caused by failure of the neural tube to close

during embryonic development. This abnormality occurs in infants born with spina

bifida.

Poliomyelitis: Polio means gray matter. This viral disease affects the gray matter of

the spinal cord, leading to paralysis of muscles that rely on the damaged neurons.

Intrathecal injection: Chemicals, such as chemotherapeutic drugs, can be

delivered into the subarachnoid space.

Hypalgesia: Diminished sensation to pain.

Hyperalgesia: It is increased sensitivity to pain.

Trigeminal neuralgia: It involves flashes of pain radiating along the course of the

trigeminal nerve.

Migraine: Migraine is a severe unilateral, vascular headache often accompanied by

photophobia. Prodromal symptoms sometimes include sensitivity to light and sound

and an aura phase of flashes before the eyes and partial blindness.

Causalgia: Intense burning pain following injury to a sensory nerve.

Coma: A coma is a state of unconsciousness from which the patient cannot be

aroused. Semicomatose refers to a stupor from which a patient can be aroused. In

an irreversible coma (brain death), there is complete unresponsibility to stimuli, no

spontaneous breathing or movement and a flat EEG.

Anesthesia: Lack of normal sensation.

Hyperesthesia: A light touch with a pin may provoke increased sensation.

Diminished sensitivity to pain is called hypesthesia.

Paresthesia: It includes burning, prickling, tingling sensations, or numbness. They

are the “pins and needles” feeling, and tingling when an extremity “falls asleep”.

Dyskinesia: Condition marked by involuntary, spasmodic movements. Tardive

(occurring late) Dyskinesia may develop in people who receive certain antipsychotic

drugs for extended periods.

Narcolepsy: Sudden, uncontrollable compulsion to sleep.

Dyslexia: Reading, writing and learning disorders.

Hemiparesis: Affects either right or left side of the body. Paresis also is used by

itself to mean partial paralysis or weakness of muscles.

Aphasia: Motor (also called Broca or expressive) aphasia is present when the

patient knows what he or she wants to say but cannot say it. The patient with

sensory aphasia articulates (pronounces) words easily but uses them inappropriately.

This patient has difficulty understanding written and verbal commands and cannot

repeat them.

Hemiplegia: Affects right or left half of the body and results from a stroke or other

brain injury. The hemiplegia is contralateral to the brain lesion because motor nerve

fibers from the right half of the brain cross to the left side of the body.

Paraplegia: Originally, the term paraplegia meant a stroke on one side. Now,

however, the term means paralysis of both legs and the lower part of the body

caused by injury or disease of the spinal cord or cauda equina.

Quadriplegia: All four extremities are affected. Injury is at the cervical level of the

spinal cord.

Syncope: Sudden and temporary loss of consciousness caused by inadequate flow of

blood to the brain.

Ataxia: Persistent unsteadiness on the feet can be caused by a disorder involving

the cerebellum.

Spina bifida: Congenital defects in the lumbar spinal column caused by imperfect

union of vertebral parts.

Hydrocephalus: Abnormal accumulation of fluid (CSF) in the brain.

Alzheimer disease: Brain disorder marked by gradual and progressive mental

deterioration with personality changes and impairment of daily functioning.

Amyotrophic lateral sclerosis: Degeneration disorder of motor neurons in the

spinal cord and brainstem.

Epilepsy: Chronic brain disorder characterized by recurrent seizure activity.

Huntington disease: Hereditary disorder marked by degenerative changes in the

cerebrum leading to abrupt involuntary movements and mental deterioration.

Multiple sclerosis: Destruction of the myelin sheath on neurons in the CNS and its

replacement by the plaques of sclerotic tissue.

Myasthenia gravis: Autoimmune neuromuscular disorder characterized by

weakness of voluntary muscles.

Parkinson disease: Degeneration of neurons in the basal ganglia, occurring in later

life and leading to tremors, weakness of muscles, and slowness of movement.

Tourette syndrome: Involuntary, spasmodic, twitching movements; uncontrollable

vocal sounds; and inappropriate words.

Herpes Zoster: Viral infection affecting peripheral nerves.

Meningitis: Inflammation of the meninges.

Cerebral concussion: Temporary brain dysfunction after injury, usually clearing

within 24 hours.

Cerebral contusion: Bruising of brain tissue as a result of direct trauma to the

head; Neurologic deficits persist longer than 24 hours.

Cerebrovascular accident: Disruption I the normal blood supply to the brain.

Electroencephalography: Recording of the electrical activity of the brain.

Stereotactic radiosurgery: Use of a specialized instrument to locate and treat

targets in the brain.