Download the nervous system

THE NERVOUS SYSTEM
HEALTH TERMS:
Neurons: Nerve Cell, unable to regenerate, two types: Sensory and Motor
Cerebrum: The largest most complex part of the brain
Cerebellum: The second largest part of the brain
Brain stem: A three-inch long stalk of nerve cells and fibers that connect the spinal cord
to the rest of the brain.
Reflex: A spontaneous response of the body to a stimulus
Dendrites: Part of the Nerve Cell, they are branching projections of the cell body-- they
receive and carry impulses to the cell body
Axon: Part of the Nerve Cell, it is a threadlike extension that carries impulses away from
the cell body
Myelin sheath: A fatty protein that covers and protects the Axon to speed the delivery of
impulses from the cell body.
Meninges: Connective tissue membranes that protect the brain and spinal cord
Peripheral: Located away from center
Epilepsy: A disorder of the nervous system that is characterized by recurrent seizures—
sudden episodes of uncontrolled electrical activity in the brain/ not a disease, but a
symptom of an underlying problem
Cerebral Palsy: a group of non-progressive neurological disorders that are the result of
damage to the brain before birth, during birth, in the newborn period, or in early
childhood.
Paraplegia: Paralysis of the lower body/ can result from a neck injury
Quadriplegia: Paralysis in both the arms and the legs/ can result from a spinal cord injury
FUNCTIONS of the NERVOUS SYSTEM:
 Acts as the body’s Communication Network and Control Center
 Controls all of the body’s actions and functions
 Senses changes in your outside environment
 Enables you to respond to stimulus within fractions of a second
STRUCTURE of the NERVOUS SYSTEM:
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Neurons
o Nerve Cell
 Dendrites they are branching projections of the cell body
 they receive and carry impulses to the cell body
 Cell Body control center of the cell
 surrounded by cell membrane
 contains nucleus
 Nucleus receives and sends nerve impulses
 regulates the amounts & types of proteins made in the cell
 Axons threadlike extension that carries impulses away from the
cell body
 covered in Myelin Sheath
 Axon Terminals Deliver and project impulses onto the Dendrites of the next
nerve cell
o Two types—classified according to their function
 Sensory- carry impulses that the body receives from the outside
environment to the CNS
 Taste, touch, see, smell, hear
 Motor- carry impulses from the CNS to the body to react to outside
stimulus

Two main divisions
o Central Nervous System
 Every body function includes CNS
 Sensory neurons bring messages from environment/ outside
stimulus to the CNS
 Motor neurons send messages from the CNS to react to outside
stimulus
 Brain largest, most complex part of Nervous System
 helps you to think, remember, reason, & coordinates
muscle movement
 involved in emotion and everything you sense
 Weighs about 3 lbs
 Reaches full size by age 6
 Uses more than 20% of Oxygen inhaled
 Protected by cranial bones, 3 layers of membranes (cranial
meninges) and cerebrospinal fluid
 Receives, processes, stores and retrieves information

Three main divisions:
o Cerebrum Largest, most complex part of brain
 Site of conscious/ intelligent thought and
activity
 Divided into two halves—hemispheres
 Right hemisphere
o controls left side of body
o Responsible for imagination,
visual thinking, spatial
relationships, form, artistic
activities, emotional
responses, color appreciation
 Left hemisphere
o controls right side of body
o Responsible for language,
logic, arithmetic calculation,
analysis, critical thinking
 Each Hemisphere has four lobes- named
after bones that protect them
o Cerebellum
 Second largest part of the brain
 Located beneath occipital lobe of cerebrum
 Controls posture, balance/ equilibrium, and
coordination
o Brain Stem
 3 inches long
 Stalk of nerves that connect brain to the
spinal cord
 Controls basic functions—breathing,
heartbeat, and eye reflexes
 Involuntary—not under conscious control
 Consists of three main parts:
 Medulla Oblongata
o Lowest part of brain stem
o Contains vital control centers
i.e. regulating heart beat,
breathing, blood pressure,
swallowing and digestion
o Also responsible for taste and
tongue movement
 Pons
o Just above medulla
o Serves mainly as a pathway
for nerve impulses to pass to
the cerebrum

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o Relays sensory info. From
ears, face, and teeth…moves
jaws and adjusts facial
expressions
Midbrain
o Shortest part of the brainstem
o Just above the Pons
o Controls eye movement and
the reactions/ size of the
pupils
o Thalamus
 Located above the midbrain
 Two egg-shaped lobes—each the size of a
walnut
 Relay center for incoming Sensory impulses
o Hypothalamus
 Located behind the eyes and under the
Thalamus
 Controls body processes i.e. regulating body
temperature, appetite for food and drink,
regulates sleep, metabolism, sexual
development, and emotional responses
Spinal Cord
 Cylinder of nerve tissue
 ~18 inches long and “index finger” thick
 Protected by vertebrae, cerebrospinal fluid and three layers
of membranes called spinal meninges
 Sprouts spinal nerves responsible for sensory and motor
neurons.
o Peripheral Nervous System
 Autonomic Nervous System
 Controls Automatics
 Involuntary Body Actions
o Sympathetic Nervous System
 Responds to the Body’s needs in
emergencies & increased activity
 Fight or Flight Response
 Rapid Pulse Rate
 Increased blood flow
 Tensed muscles
o Parasympathetic Nervous System
 Opposes the actions of the Sympathetic N.S.
 Slows Heart Rate
 Returns Body back to normal

Somatic Nervous System
 Transmits impulses to Skeletal muscles
 Responsible for Voluntary Body Actions
CARE of the NERVOUS SYSTEM:

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Regular Exercise
Proper nutrition
Adequate Rest and Sleep
Avoid Alcohol & Drugs
Follow basic safety rules
o Wear seat belt in car
o Check depth of water before diving
o Wear a helmet when riding a bike, motorcycle, skateboarding, riding
scooter, in-line skating, or playing contact sports
INJURIES of the NERVOUS SYSTEM:
 More than ½ million people are hospitalized for Brain/ Spinal Injuries
 20% suffer life-long mental or physical impairment


Head Injuries
o Concussion
 Temporary disturbance of the brain’s ability to function
 Most common and Mildest of Head injuries
o Contusion
 Brain bruise
 Causes swelling to the brain
 Can result in coma—state of unconsciousness
Spinal Cord Injuries
o Quadriplegia
 Permanent damage to the spinal cord
 Paralysis in both arms and legs
o Paraplegia
 Permanent damage to the spinal cord
 Paralysis in lower body
ILLNESSES of the NERVOUS SYSTEM:
 Degenerative Diseases—breakdown or deterioration of function or structure of
the system
o Parkinson’s Disease
 Progressive Degeneration of nerve cells within the brain that
regulate motor impulses
 Result = uncoordinated muscular movement
o Multiple Sclerosis
 Progressive destruction of the myelin sheath that surrounds nerve
fibers in the brain and spinal cord

Thought to be an auto-immune disease—body recognizes myelin
sheath as a foreign invader and attacks it
 The Underlying nerve cells are damaged
 Voluntary control of muscles gradually decreases
o Alzheimer’s Disease
 General mental deterioration.
 Gradual memory loss and power of judgment affected
 Speech and body coordination affected
 No cure
 Fourth leading cause of death in adults

Disorders with Unknown Causes
o Epilepsy
 Seizure disorder
 Not a disease but symptom to underlying problem
 May result from chemical imbalance in brain, head injury, tumor,
congenital brain injury, infection, stroke or withdrawl from drugs
 Medication can help to control the seizures
o Cerebral Palsy
 Congenital in nature
 Can result from Oxygen deficiency, Accidental injury, radiation,
certain drugs, and diseases such as encephalitis (water on the
brain) and meningitis (infection of the spinal cord)
 Certain cause is unknown
 Physical Therapy, braces, walking aids can help patients to live full
active lives.