Ch 10 Nervous System Vocab

Nervous system function

Carries electrical messages throughout the body; controls voluntary and involuntary functions; has external and internal receptors; made of about 100 billion nerve cells

Neuron impulse pathway (3 steps)

1) Stimuli activate cell membranes to release the nervous impulse; 2) Receptors receive and transmit impulses to the brain and spinal cord (CNS); 3) CNS recognizes, interprets, and relays impulses to muscles, glands, and organs

Two major divisions of the nervous system

Central nervous system (CNS) and Peripheral nervous system (PNS)

Central nervous system (CNS) consists of

The brain and spinal cord

Peripheral nervous system (PNS) consists of

Cranial nerves, spinal nerves, and autonomic nerves

Cranial nerves

12 pairs; carry impulses between the brain and the head/neck (except the vagus nerve)

Spinal nerves

31 pairs; carry impulses between the spinal cord and the chest, abdomen, and extremities

Sensory (afferent) nerves

Carry messages toward the brain

Motor (efferent) nerves

Carry messages away from the brain

Mixed nerves

Carry both sensory and motor fibers

Afferent neurons

Bring impulses from sensory receptors into the spinal cord; "the sensing neurons," travel toward the spinal cord

Efferent neurons

Carry impulses from the spinal cord to effector organs; "the action neurons," travel away from the spinal cord

Autonomic nervous system

Carries impulses from the CNS to the organs; controls involuntary functions of the heart, blood vessels, glands, intestines, stomach, and bladder

Sympathetic nerves

Stimulate the body under stress

Parasympathetic nerves

Balance the sympathetic system; slow heart rate and lower blood pressure

Neuron

Individual nerve cell; parenchyma (functional tissue) of the nervous system; carries impulses throughout the body

Parts of a neuron

Dendrite, cell body/nucleus, axon (with myelin sheath and neurilemma), and terminal end fibers

Dendrite

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

Axon

Microscopic fiber that carries the nervous impulse along a nerve cell

Myelin sheath

Covering of white fatty tissue that surrounds and insulates the axon; speeds impulse conduction

Terminal end fibers

Secrete neurotransmitters that transfer the impulse across the synapse

Synapse

The space through which a nervous impulse travels between nerve cells or between a nerve and a muscle/glandular cell

Neurotransmitter

Chemical messenger released at the end of a nerve cell that stimulates or inhibits another cell

Acetylcholine

Neurotransmitter chemical released at the ends of nerve cells

Ganglion (plural: ganglia)

Collection/small cluster of nerve cell bodies, located in the peripheral nervous system

Glial cells (neuroglial cells)

Supportive, protective, and connective cells of the CNS; do not transmit impulses; can reproduce themselves; maintain the health of the nervous system

Four types of glial cells

Astrocytes, microglia, oligodendroglia, and ependymal cells

Astrocyte

Glial cell that transports water and salts between capillaries and neurons

Microglial cell

Phagocytic glial cell that protects neurons/removes waste products in response to inflammation

Oligodendroglial cell (oligodendrocyte)

Glial cell that forms the myelin sheath covering axons

Ependymal cell

Glial cell that lines membranes within the brain and spinal cord; helps form cerebrospinal fluid (CSF)

Stroma

Connective and supporting tissue of an organ; glial cells are the stromal tissue of the brain

Nerve

Macroscopic cord-like collection of fibers (axons and dendrites) that carry electrical impulses

Cerebrum

The largest part of the brain; divided into right and left hemispheres; responsible for voluntary muscle activity, vision, speech, taste, hearing, thought, and memory

Four major lobes of the cerebrum

Frontal lobe, parietal lobe, temporal lobe, and occipital lobe

Frontal lobe function

Thought processes, behavior, personality, emotion, and body movement

Parietal lobe function

Body sensations, visual and spatial perception

Temporal lobe function

Hearing, understanding speech, language

Occipital lobe function

Vision

Cerebral cortex

Outer region of the cerebrum; contains sheets of nerve cells (gray matter); manages speech, vision, smell, movement, hearing, and thought

Gyrus (plural: gyri)

Sheet of nerve cells that produces a rounded ridge/fold on the surface of the cerebral cortex; convolution

Sulcus (plural: sulci)

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

Corpus callosum

Structure lying in the center of the brain that connects the two cerebral hemispheres

Basal ganglia

A group of cells that regulate intentional (voluntary) movements of the body

Cerebellum

Posterior part of the brain; coordinates voluntary muscle movements and maintains balance

Thalamus

Main relay center of the brain; integrates and monitors impulses from the skin (pain); conducts impulses between the spinal cord and cerebrum

Hypothalamus

Portion of the brain beneath the thalamus; controls body temperature, sleep, appetite, sexual desire, and emotions; regulates pituitary hormone release; monitors sympathetic/parasympathetic systems

Brainstem

Posterior portion of the brain that connects the cerebrum with the spinal cord; consists of the pons and medulla oblongata

Pons

Bridges the cerebrum and cerebellum with the rest of the brain; houses nerves for the face and eyes

Medulla oblongata

Part of the brain just above the spinal cord; connects the spinal cord to the brain; controls breathing, heartbeat, and size of blood vessels

Spinal cord

Column of nervous tissue extending from the medulla oblongata to the second lumbar vertebra; serves as a pathway for impulses to and from the brain

Gray matter

The inner section of the cross section of the spinal cord

White matter

The outer section of the cross section of the spinal cord

Cauda equina

Collection of spinal nerves below the end of the spinal cord

Meninges

Three protective connective tissue membranes that surround the brain and spinal cord

Dura mater

Thick, outermost layer of the meninges; channels blood to brain tissue

Arachnoid membrane

Middle layer of the three meninges

Pia mater

Thin, delicate, innermost membrane of the meninges; offers a rich supply of blood vessels

Cerebrospinal fluid (CSF)

Fluid that lies between the arachnoid membrane and the subarachnoid space; circulates through the brain and spinal cord; provides protection, buoyancy, and chemical stability

Ventricles of the brain

Canals in the brain that contain cerebrospinal fluid

Blood-brain barrier

Protective separation between blood and brain cells that keeps substances (such as anticancer drugs) from penetrating capillary walls and entering the brain

Central nervous system (CNS)

The brain and spinal cord

Cranial nerves definition

Twelve pairs of nerves that carry messages to and from the brain regarding the head and neck (except the vagus nerve)

Peripheral nervous system definition

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

Parenchyma

Essential, distinguishing tissue of any organ or system; for the nervous system, this is neurons and nerves that carry impulses

Plexus (plural: plexuses)

A large, interlacing network of nerves

Receptor

An organ that receives a nervous stimulus and passes it to afferent nerves; skin, ears, eyes, and taste buds are receptors

Sciatic nerve

The nerve extending from the base of the spine down the thigh, lower leg, and foot

Stimulus (plural: stimuli)

An agent of change (light, sound, touch) in the internal or external environment that evokes a response

Vagus nerve

Tenth cranial nerve; branches reach the larynx, trachea, bronchi, lungs, aorta, esophagus, and stomach

Anencephaly

Congenital absence of major brain structures

Hydrocephalus

Congenital disorder involving abnormal accumulation of fluid (CSF) in the brain; treated with a shunt catheter placed from a brain ventricle into the peritoneal space or right atrium of the heart for continuous drainage

Spina bifida

Congenital defect in the lumbar spinal column caused by imperfect union of vertebral parts (a neural tube defect)

Spina bifida occulta

Posterior vertebrae have not fused; no herniation of the spinal cord or meninges; may show skin signs like a mole, dimple, or patch of hair

Spina bifida cystica with meningocele

External protruding sac contains meninges and CSF

Spina bifida cystica with myelomeningocele

External sac contains meninges, CSF, and the spinal cord; often associated with hydrocephalus and paralysis

Alzheimer disease (AD)

Brain disorder marked by gradual, progressive mental deterioration (dementia), personality changes, and impairment of daily functioning; occurs in midlife, progresses after age 70; no effective treatment

Amyotrophic lateral sclerosis (ALS)

Degenerative disorder of motor neurons in the spinal cord and brainstem

Epilepsy

Chronic brain disorder characterized by recurrent seizure activity from abnormal, sudden electrical discharges within the brain; can be caused by brain tumor, meningitis, vascular disease, or scar tissue

Tonic-clonic seizure (grand mal)

Sudden loss of consciousness, falling down, tonic contractions (muscle stiffening), then clonic contractions (twitching/jerking of limbs)

Aura

A peculiar sensation occurring before a seizure

Huntington disease (Huntington chorea)

Hereditary disorder with degenerative changes in the cerebrum leading to abrupt involuntary movements and mental deterioration

Multiple sclerosis (MS)

Destruction of the myelin sheath on neurons in the CNS and its replacement by plaques of sclerotic (hard) tissue

Myasthenia gravis (MG)

Autoimmune neuromuscular disorder characterized by weakness of voluntary muscles

Palsy

Paralysis; partial or complete loss of motor function

Bell palsy (Bell's palsy)

Paralysis on one side of the face

Parkinson disease

Degeneration of neurons in the basal ganglia occurring in later life, leading to tremors, muscle weakness, and slowness of movement; caused by a deficiency of dopamine; drug therapy is palliative, not curative

Tourette syndrome

Disorder involving involuntary, spasmodic, twitching movements, uncontrollable vocal sounds, and inappropriate words

Herpes zoster (shingles)

Viral infection (herpes zoster virus) affecting peripheral nerves, causing blisters in a band-like pattern on the body

Meningitis (leptomeningitis)

Inflammation of the meninges

Pyogenic meningitis

Inflammation of the meninges with pus formation

HIV encephalopathy

Brain disease/dementia occurring with AIDS

Cerebral concussion

Temporary brain dysfunction after injury; may show no structural damage or loss of consciousness; rest is important; usually clears within 24 hours

Cerebral contusion

Bruising of brain tissue from direct trauma to the head; usually associated with skull fracture, edema, and increased intracranial pressure; neurological deficits persist longer than 24 hours

Cerebrovascular accident (CVA / stroke)

Disruption in the normal blood supply to the brain

Thrombotic stroke

Caused by a blood clot in an artery leaving the brain (atheromatous plaques occluding cerebral arteries)

Embolic stroke

Caused by a dislodged clot (embolus) that travels to and occludes the cerebral arteries

Hemorrhagic stroke

Caused by rupture of a blood vessel, such as a cerebral artery, with resulting bleeding

Migraine

A severe, recurring, unilateral, vascular headache

Subdural hematoma

Collection of blood in the subdural space (between the dura mater and arachnoid membrane), often from venous bleeding