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Health Occupations
Nervous System
Nervous System
Complex & highly organized
 Coordinates all of the many activities of
the body
 Allows body to respond and adapt to
changes that occur both inside and
outside of the body
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Neuron
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Also called nerve cell
 Basic structural unit of nervous system
 Parts of neuron
– Cell body
– Nucleus inside cell body
– Nerve fibers
• Dendrites – carry impulses to cell body
• Axon – carry impulses away from cell body
– Many covered with myelin sheath (fat covering)
– Increases rate of transmission of impulses
– Insulates & maintains the axon
Neuron
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Axon lies close to dendrites of many other
neurons
– Synapse – space between neurons
– Impulses coming from an axon jump synapse to
get to the dendrite of a neuron that will carry the
impulses in the right direction
– Neurotransmitters – special chemicals located at
end of axon to allow impulses to pass from neuron
to another
– Impulses may follow many different routes
1. Dendrites
3. Nucleus
4. Axon
5. Myelin Sheath
2. Cell body
6. Terminal
branches
Nerves
Combination of many nerve fibers
 Located outside brain & spinal cord
 Afferent – sensory
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– Messages to brain & spinal cord
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Efferent – motor
– Messages from brain & spinal cord
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Associative – both sensory & motor
Divisions of nervous system
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Central nervous system
– Brain
– Spinal cord
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Peripheral nervous system
– Nerves
– Autonomic nervous system
• Separate division of peripheral nervous system
• Controls involuntary body functions
Central nervous system
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Brain
– Mass of nerve tissues
– Protected by membranes & cranium
– Cerebrum
• Largest & highest section of brain
• Convolutions – folds found on outer part
• Lobes
– Frontal, parietal, temporal, occipital
– Named after bones that surround them
• Responsible for reasoning, thought, memory, speech,
sensation, sight, smell,hearing, & voluntary body
movement
Brain
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Cerebellum
– Below back of cerebrum
– Responsible for coordination of muscles, balance,
posture, muscle tone
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Diencephalon
– Between cerebrum & midbrain
– Thalamus
• Relay center to direct sensory impulses to cerebrum
– Hypothalamus
• Regulates & controls ANS, temperature, appetite, water
balance, sleep, constriction & dilation of blood vessels,
anger, fear, pleasure, pain, affection
Brain
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Midbrain
– Below cerebrum at top of brain stem
– Responsible for conducting impulses
between brain parts & eye reflexes
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Pons
– Below midbrain in brain stem
– Responsible for conducting messages to
other parts of brain & reflexes like chewing,
tasting, production of saliva, respiration
Brain
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Medulla oblongata
– Lowest part of brain stem
– Connects with the spinal cord
– Responsible for regulating heartbeat,
respiration, swallowing, coughing, & blood
pressure
Ventricles
Convolutions
Cerebrum
Cerebellum
Midbrain
Pons
Medulla oblongata
Spinal cord
Spinal cord
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Continues down from the medulla oblongata
Ends at L1 or L2
Surrounded & protected by vertebrae
Responsible for many reflexes
Carries sensory messages to brain (afferent)
Carries motor messages away from brain
(efferent)
Meninges
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3 membranes
Cover & protect brain & spinal cord
Dura mater – thick, tough outer layer
Arachnoid membrane – middle layer, delicate
& weblike
Pia mater – innermost layer
– Closely attached to brain & spinal cord
– Contains blood vessels that nourish nerve tissue
Ventricles
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4 hollow spaces located in brain
 Connect with each other & with subarachnoid
space
 Filled with CSF
– Fluid circulates continually between ventricles &
through subarachnoid space
– Serves as shock absorber
– Carries nutrients to brain & spinal cord
– Helps remove metabolic products & wastes
– Produced by choroid plexuses in ventricles
– After circulating, absorbed into blood vessels of
the dura mater & returned to bloodstream through
arachnoid villi
Peripheral Nervous System
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Made up of all the nerves
 Consists of cranial nerves & spinal nerves
 Cranial nerves
– 12 pairs & branches
– Responsible for special senses like sight, hearing,
taste, smell
– Receive general sensations like touch, pressure,
pain, temperature
– Send out impulses for voluntary & involuntary
muscle control
Peripheral Nervous System
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Spinal nerves
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31 pairs & branches
Carry messages to & from spinal cord
Sensory & motor
8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 pair of
coccygeal spinal nerves
– Each nerve goes directly to a particular part of the
body or networks with other spinal nerves to form
a plexus, supplying sensation to a larger segment
of the body
Autonomic Nervous System
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Part of PNS
 Helps maintain a balance in the involuntary
functions of body, but allows body to react in
emergency
 2 divisions – sympathetic & parasympathetic
– Usually 2 systems work together
– Maintain homeostasis
– Controls involuntary body functions at proper rates
Autonomic Nervous System
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Sympathetic
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Acts in time of emergency – fight/flight
Prepares body to act
Increases heart rate, respirations, BP
Slows activity in digestive tract
Parasympathetic
– Counteracts actions of sympathetic after
emergency is over
– Slows heart rate, respirations
– Lowers BP
– Increases digestive activity
Diseases & Abnormal Conditions
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Cerebral Palsy
– Disturbance in voluntary muscle action
– Caused by brain damage
• Lack of oxygen to brain &/or birth injury
• Prenatal rubella (German measles) & infections
– Spastic, athetoid, & atactic (most common)
– Symptoms
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Exaggerated reflexes & seizures
Tense muscles & contractures
Speech impairment
Muscle spasms & tremors
Mental retardation in some cases
Cerebral palsy
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Treatment but no cure
– PT, OT, & speech tx
– Muscle relaxants & anticonvulsive druges
– Casts & braces
– Orthopedic surgery for severe contractures
Cerebrovascular Accident (CVA)
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Stroke, apoplexy
 Blood flow to brain is impaired resulting in
lack of oxygen & destruction of brain tissue
 Causes
– Cerebral hemorrhage
• HTN
• Aneurysm
• Weak blood vessel
– Occlusion or blockage
• Atherosclerosis
• Thrombosis (blood clot)
CVA
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Symptoms – vary depending on area &
amount of brain tissue damaged
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Loss of consciousness
Weakness & vertigo
Hemiplegia (paralysis on 1 side)
Dysphagia (difficulty swallowing)
Visual disturbances & difficulty swallowing
Aphasia (speech impairment)
Incontinence
CVA
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Immediate treatment
– 1st THREE hours
– Thrombolytic (clot busting) drugs
– Angioplasty of cerebral arteries
– CT scans needed to determine cause
– Neuroprotective agents can be used to
prevent permanent brain damage to
neurons
CVA
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Treatment
– Depends on symptoms present
– Directed toward helping person recover
from OR adapt to symptoms present
– PT, OT, speech therapy ESSENTIAL
Encephalitis
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Inflammation of brain caused by virus,
bacteria, or chemical agent
 Mosquitoes are common vector
 Symptoms vary – fever, extreme weakness,
lethargy, visual changes, HA, N & V, stiff neck
& back, seizures, coma
 Treatment – supportive
– Antiviral & antiseizure meds
– Maintenance of fluids & electrolytes
– Monitoring of respiratory & kidney function
Epilepsy
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Brain disorder associated with abnormal
electrical impulses in neurons of brain
 Causes – brain injury, birth trauma, tumors,
toxins (lead & carbon monoxide)
 Many cases are idiopathic
 Absence (Petit mal) seizures
– Milder, characterized by loss of consciousness
lasting several seconds
– Common in children
– Usually disappears by late adolesence
Epilepsy
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Tonic-clonic (grand mal) seizures
– Most severe
– Loss of consciousness lasting at least several
minutes
– Convulsions with violent thrashing movements &
shaking
– Hypersalivation, foaming at mouth
– Loss of body functions
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Treatment – antiseizure medications
Hydrocephalus
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Excessive accumulation of CSF in ventricles
& subarachnoid space
 Usually caused by congenital defect,
infection, or tumor that obstructs the flow of
CSF
 Symptoms –
– Abnormally large head & prominent forehead with
bulging eyes
– Irritability
– Distended scalp veins
– Retardation when pressure prevents proper
development of brain
Hydrocephalus
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Treatment – surgical implantation of a
shunt between ventricles & veins, heart,
or abdominal peritoneal cavity to drain
excess CSF
Meningitis
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Inflammation of meninges of brain &/or spinal
cord caused by bacteria, fungus, virus, or
toxins (lead, arsenic)
 Symptoms
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High fever
HA, back & neck pain, stiffness
N&V
Delirium & confusion
Coma & death if untreated
Treatment – antibiotics, anticonvulsants,
meds for pain & cerebral edema
Multiple Sclerosis
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Chronic, progressive, disabling condition
resulting from degeneration of the myelin
sheath in the CNS
Usually occurs between 20 – 40
Unknown cause
Progresses at different rates
Early symptoms
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Visual disturbances
Weakness, fatigue
Poor coordination
Tingling & numbness
Multiple sclerosis
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Later symptoms
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Tremor, spasticity of muscles
Paralysis
Speech impairment
Emotional swings
incontinence
Treatment – PT, muscle relaxants, steroids,
psychological counseling
 Goal is to maintain functional ability
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Neuralgia
Nerve pain
 Caused by inflammation, pressure,
toxins, & other diseases
 Treatment directed towards eliminating
cause
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Paralysis
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Brain or spinal cord injury destroys neurons &
results in loss of function & sensation below
level of injury
Hemiplegia – paralysis on 1 side of body
Paraplegia – paralysis in lower extremities
Quadriplegia – paralysis of arms, legs, &
body
No cure, research being done towards repair
Treatment – supportive, PT, OT
Parkinson’s Disease
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Chronic progressive condition involving
degeneration of brain cells
 Usually occurs in people over 50
 Symptoms
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Tremors, stiffness, muscle rigidity
Forward leaning position & shuffling gait
Difficulty stopping when walking
Loss of facial expression & drooling
Mood swings with frequent depression
Behavior changes
Parkinson’s Disease
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Treatment but no cure
– Levodopa used to relieve symptoms
– In selected cases, surgery to selectively
destroy a small area of brain to control
involuntary movements or implant a device
– PT to treat rigidity
Shingles or herpes zoster
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Acute inflammation of nerve cells
Caused by herpes virus, similar to chicken
pox
Characteristically, occurs in thoracic area on
1 side of body & follows path of the affected
nerves
Symptoms – fluid filled vesicles, severe pain,
redness, itching, fever, abnormal skin
sensations
Treatment – relief of pain & itching until
inflammation subsides, usually 1-4 weeks