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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
Cerebrum
Cerebellum
Medulla
Oblongata
Two hemispheres divided by a fissure
Lobes
frontal, parietal, temporal, occipital
Cortex, 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
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