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Medical Terminology

Nervous System

Chapter 15

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Nervous System

Coordinates many activities of the body– senses changes in internal and external

environment– interprets these changes– coordinates appropriate response in order

to maintain homeostasis When the brain ceases functioning, the

body dies

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Structures

nerve is one or more bundles of impulse carrying fibers that connect the brain & spinal cord with body

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Nervous Tissue

Neurons - transmit impulses– sensory (afferent, ascending)– motor (efferent, descending)

Neuroglia - support neurons

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Neuron dendrites-rootlike structures that receive

impulses and conduct them to the cell body

cell body - contains nucleus axon-extends away from the cell body

and conducts impulses away from the nerve cell

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Neuron Anatomy

Myelin sheath - – insulation– accelerates impulse transmission– appears as white covering

myelin on axons in brain and spinal cord gives white appearance

unmyelinated fibers, dendrites, and nerve cell bodies comprise gray matter of brain and spinal cord

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Neuron Anatomy(peripheral nerves)

Schwann cell– type of neuroglial cell wrapped around

axon – forms the myelin sheath

Neurolemma (neurolemmal sheath)– permits a damaged axon to regenerate– neurolemma NOT found in Central nerves

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Neurotransmitters

Synapse- space between two neurons or between a neuron and a receptor organ.

Impulses are passed from one neuron to another at a junction called the synapse.

Electrical current within neuron causes release of chemical substance called a neurotransmitter.

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Neurotransmitter diffuses across the synapse to receptor sites on the dendrite of the next neuron.

Generates the next electrical stimulus. Terminal ends of the axon release a transmitter

substance that affects the dendrites of the next neuron.

One way transmission of the impulse is assured because only the axons release these chemicals.

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Neuroglia

gli/o or nerve glue neuroglia or glial cells astrocytes - blood brain barrier oligodendrocytes - facilitate myelin

development microglia - phagocytic properties ependyma - assist in CSF circulation

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Divisions

Central Nervous System– brain and spinal cord

Peripheral Nervous System– cranial nerves and spinal nerves

– fibers are sensory or motor

Autonomic Nervous System– ganglia on either side of the spinal cord

sympathetic nervous system parasympathetic nervous system

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Brain

Cerebrum Cerebellum Diencephalon Brainstem

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Cerebrum

Cerebellum

MedullaOblongata

Cerebrum

Two hemispheres divided by a fissureLobes frontal, parietal, temporal, occipitalCortex, gray color

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Lobes Frontal

– motor functions Parietal

– receives & interprets information Occipital

– eyesight Temporal

– hearing & smell

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Cerebellum

receives incoming messages regarding movement within joints, muscle tone, and position of the body.

relay these messages to other parts of brain to control skeletal activity

movement, coordination, balance

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Thalamus

below the cerebrum monitors sensory stimuli by suppressing

some and magnifying others

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Hypothalamus-a regulator

Autonomic Nervous System emotional responses/behavior body temperature food intake= hunger water balance and thirst sleep-wake cycles endocrine system activity

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Brainstem

stalk-like portion of the brain– midbrain - conduction pathways– pons - nerve cells cross from one side to

the other– medulla oblongata - basic life functions

origin for 10 of 12 cranial nerves– controls respiration, blood pressure, heart

rate

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Spinal Cord housed within vertebral column continuos with brain stem ascending and descending nerve tracts protected by CSF and meninges gray matter in internal section - not

protected by myelin sheath myelinated white matter in outer area

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Meninges dura mater

– epidural– subdural

arachnoid – subarachnoid space– contains CSF

pia mater– blood vessels and lymph

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Bell’s Palsy

Facial paralysis– functional disorder of VII cranial nerve– asthenia– keratitis– dysphasia

Treatment– anti-inflammatory drugs

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Cerebrovascular Disease

Arteriosclerosis cerebrovascular accident (CVA, apoplexy)

– ischemia– transient ischemic attack– hemiparesis– hemiplegia– aphasia– ataxia

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Seizure Disorders

Epilepsies– dysrhythmias in the brain– etiology: brain injury, congenital anomalies,

metabolic disorders, brain tumors Convulsions

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Parkinson’s Disease

Progressive neurological disorder– deterioration of portion of brain controlling

movement– bradykinesia, hypokinesia, tremors,

shuffling gait. Treatment: l-dopa

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Multiple Sclerosis

Progressive degenerative disease of CNS Inflammation, hardening, and loss of myelin

throughout spinal cord and brain Impeded transmission of electrical impulses tremors, muscle weakness, slowness of

movements etiology: autoimmune, or slow virus

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Alzheimer’s Disease Progressive neurological disorder plaques develop in cerebral cortex memory loss, cognitive decline, and

personality changes leading cause of senile dementia research: some meds prevent

breakdown of brain chemicals

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Oncology

Intracranial tumors– primary sites– metastatic sites

Signs and Symptoms– headaches– papilledema– personality changes

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Agnosia asthenia ataxia cerebral palsy closed head trauma coma concussion Guillian-Barre syndrome herpes zoster (shingles)

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Huntington’s chorea hydrocephalus lethargy neural tube defect paraplegia paresis

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Paresthesia poliomyelitis quadriplegia Reye’s syndrome sciatica syncope

– vasovagal transient ischemic attack (TIA)

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Cerebral angiography echoencephalography electroencephalography (CCG) myelography computed tomography (CT scan)

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Surgical and Therapeutic Procedures

Cryosurgery spinal puncture, spinal tap trephination vagotomy

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Pharmacology Analgesics \anticonvulsants antidepressants hyponotics opiates psychtropic drugs sedatives tranquilizers

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Abbreviations

ALS ANS CNA CP CSF CT scan CVA CVD

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Abbreviations

EEG ICP LP MRI MS R/O TIA

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End

Chapter 15

Nervous System