Nervous System
Please be sure to study and take
notes.
What is the nervous system?
• A complex, organized system that coordinates
all the activities of the body
• ***Enables the body to respond and adapt to
changes that occur both inside and outside
the body ***
• Neuron (nerve cell) is the basic structural unit
of the nervous system
– The neuron consists of :
• Cell body containing a nucleus
• Nerve fibers called dendrites which carry impulses toward
the cell body
• Single nerve fiber called an axon which carries impulses
away from the cell body (Axons have a lipid covering called
myelin sheath, which increases impulse transmission and
insulates the axon)
• Axon of one neuron lies close to the dendrites of many other
neurons----Space between them are know as synapses
-Impulses coming from an axon “jump” the synapse
to get to the dendrite that will carry the impulse in
the right direction
-Neurotransmitters located at the end of each axon
allow nerve impulses to pass from one neuron to
another
YOU ARE GETTIN’ ON MY
NERVES
• So, what are “nerves”
– Combination of nerve fibers (bundles of axons)
– Located outside the brain and spinal cord
– Afferent (sensory) nerves carry messages from all
parts of the body to the brain and spinal cord
– Efferent (motor) nerves carry messages from the
brain and spinal cord to muscles and glands
– Associative nerves carry both sensory and motor
messages
2 divisions of the nervous system
1. Central nervous system (CNS)
- Consists of the brain and spinal cord
- BRAIN
-
Mass of nerve tissue, protected by the cranium (skull)
Sections of the brain
-
1. Cerebrum= largest section of the brain
- Outer part is arranged in folds called convolutions
- Separated into lobes- frontal, parietal, temporal, occipital
- Responsible for reasoning, thought, memory, judgment,
speech, sensation, sight, smell, hearing, and voluntary body
movements
Sections of the brain continued
• 2. Cerebellum
– Section below the back of the cerebrum
– Responsible for muscle coordination, balance, posture,
and muscle tone
3. Diencephalon
-
Located between the cerebrum and midbrain
Contains two structures
- 1. thalamus- allows conscious recognition of pain and
temperature
- 2. hypothalamus-regulates and controls the autonomic
nervous system, temperature, appetite, water balance, sleep,
and blood vessel constriction and dilation; also involved in
emotions such as anger, fear, pleasure, pain, and affection
Sections of the brain continued
• 4. Midbrain
– Located below the cerebrum at the top of the brainstem
– Responsible for impulses between brain parts and for certain eye and
auditory reflexes
5. Pons
-located below the midbrain and in the brainstem
-Responsible for conducting messages to other parts of the brain and
for reflex actions like chewing, tasting, producing saliva, and assisting
with respiration
6. Medulla Oblongata
-lowest part of the brainstem, connects with the spinal cord
-Responsible for regulating heartbeat, respiration, swallowing,
coughing, and blood pressure
• SPINAL CORD
• Continues from the medulla oblongata and ends at the first or second vertebrae
• Surrounded and protected by the vertebrae
• Responsible for carrying afferent (sensory) messages up to the brain and carrying efferent
(motor) messages from the brain to the nerves that go muscles and glands
-You have three membranes called meninges that cover and protect
the brain and spinal cord
- Dura mater- thick, tough, outer layer
- Arachnoid membrane- middle layer; delicate weblike
layer that is attached to other meninges to allow space for fluid to
flow between the layers
-Pia Mater- innermost layer, closely attached to the brain
and spinal cord; contains blood vessels that nourish the nerve tissue
Ventricles
• Brain has 4 ventricles
• What are they? Hollow spaces that connect
with each other and with the space under the
arachnoid membrane (middle layer membrane that covers
and protects the brain and spinal cord)
• Ventricles are filled with clear, colorless fluid
called cerebrospinal fluid
Functions of cerebrospinal fluid
• Circulates continually between the ventricles
• Serves as shock absorber to protect the brain and
spinal cord
• Carries nutrients to some parts of the brain and
spinal cord
• Helps remove wastes
• After circulating it is absorbed into the blood
vessels of the dura mater (thick, tough, outer layer membrane
that covers and protects the brain and spinal cord) and returned to
the bloodstream
• 2. Peripheral Nervous System (PNS)
• Consists of the somatic and the autonomic nervous systems
• - Somatic Nervous System
– Consists of 12 pairs of cranial nerves and 31 pairs of
spinal nerves
» Spinal nerves carry messages to and from the spinal
cord and are mixed nerves—afferent (sensory) and
efferent (motor)
• 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 pair
of coccygeal
12 pairs of cranial nerves
•
•
•
•
•
•
•
•
•
•
•
•
I. Olfactory Nerve– smell
II. Optic nerve- vision
III. Oculomotor nerve- eye movement, pupil regulation
IV. Trochlear nerve- eye movement
V. Trigeminal nerve- (largest cranial nerve)sensations to head and face, mastication
(chewing)
VI. Abducens nerve-eye movement
VII. Facial nerve- taste receptors, facial expressions
VIII. Vestibulocochlear Nerve- hearing, sense of balance (equilibrium)
IX. Glossopharyngeal Nerve- sensations to tongue and pharynx- swallowing/saliva
X. Vagus nerves- speech (larynx) and swallowing, slows heart rate, digestion
XI.Accessory nerves- controls muscles used in head movement (neck/back-spinal
branch); (cranial branch- transmit impulses of soft palate, pharynx, larynx)
XII. Hypoglossal nerves- tongue movement
• Autonomic Nervous System
– Helps maintain a balance in the involuntary
functions of the body and allows the body to react
in times of emergency
– Has 2 divisions= sympathetic and parasympathetic
nervous systems
– **** These two divisions/systems work together
to maintain a balanced state called ___________.
Sympathetic
• Acts in times of emergency– “Fight or flight”
• Prepares the body to act
• Increases heart rate and respirations, raises
blood pressure, slows activity in digestive tract
Parasympathetic
• Counteracts actions of sympathetic system
after an emergency
• Slows heart rate and respirations, lowers
blood pressure, increases activity in the
digestive tract
Diseases/Conditions of Nervous
System
• Amyotrophic Lateral Sclerosis (ALS)
–
–
–
–
–
–
–
–
–
AKA Lou Gehrig’s Disease
Chronic, degenerative neuromuscular dz
Cause is unknown (?genetic, ?viral/immune factors)
Nerve cells in the CNS that control voluntary movement degenerate
R/I weakening and atrophy of muscles they control
Initial sx: muscle weakness, abnormal reflexes , tripping/falling,
impaired hand/arm movements, difficulty speaking and swallowing
As dz progresses, more muscles are affected, R/I in total body paralysis
Late stages of dz- loses all ability to communicate, breathe, eat, and
move
* Mental acuity is unaffected
No treatment but meds to slow progression of dz
Carpal Tunnel Syndrome
– Condition occurs when the medial nerve and tendons that
pass through a “tunnel” on their way from the forearm to
the hands ad fingers are pinched
– Repetitive movement of the wrist causes swelling around
this tunnel, which puts pressure on nerves/tendons
– Sx:- pain, muscle weakness in hand, impaired movement
– Classic Sx: pain, numbness/tingling in thumb, ring finger,
and middle finger
– Tx: anti-inflammatory meds, pain meds, splinting to
immobilize joint; surgery to enlarge the tunnel and relieve
pressure on nerves/tendons
Cerebral Palsy
– Disturbance in voluntary muscle action
– Caused by brain damage
• Lack of O2 to the brain and/or birth injuries
• Prenatal rubella (German measles)
• Prenatal infections
Spastic is the most common form of cerebral palsy
Sx: exaggerated reflexes and seizures, tense muscles and
development of contractures, speech impairment, spasms,
tremors, mental retardation in some cases
Tx: (no cure) PT, OT, speech therapy. Muscle relaxants,
anticonvulsive meds, braces, orthopedic surgery if needed for
severe contractures
Cerebrovascular Accident (CVA)
– AKA stroke
– Blood flow to the brain is impaired, R/I lack of O2 and
destruction of brain tissue
– Causes: cerebral hemorrhage from HTN, aneurysm, or
a weak blood vessel; blockage caused by
atherosclerosis or a thrombus
– Risk factors: smoking, high fat diet, obesity, sedentary
lifestyle
– Sx: LOC, weakness, vertigo, paralysis on one side of
the body, dysphagia (difficulty swallowing). Mental
confusion, aphasia (speech impairment), incontinence
CVA (continued)
• Immediate care within the first 3 hours can
help prevent brain damage
• Treatment with “clot busting” drugs (TPA) or
angioplasty of cerebral arteries can dissolve a
clot and restore blood flow to the brain
• CT scans are used to determine cause of CVA
(IF CVA is caused by a hemorrhage a “clot
busting” drug cannot be used)
• May need PT, OT, speech therapy
Encephalitis
• Inflammation of the brain caused by a virus,
bacterium, chemical agent, or as a complication
of measles, mumps, chicken pox
• ** frequently contracted from a mosquito
(mosquitos carry encephalitis virus)
• Sx– fever, extreme weakness (lethargic), visual
disturbances, headaches, vomiting,
disorientation, seizures, coma
• Tx- antiviral meds, maintain fluid and electrolyte
balance, antiseizure meds, watch respiratory and
kidney functions
Epilepsy (Seizures)
• Brain disorder associated with abnormal electrical
impulses in the neurons of the brain
• Causes can include brain injury, birth trauma, tumors,
toxins, infections, and many are idiopathic
• Petit mal seizures- milder, LOC lasting a few seconds
• Grand-mal seizures- most severe, LOC lasting a few
minutes, convulsions with violent shaking, foaming at
the mouth (hypersalivation), loss of body functions
• Some people may experience an aura just before a
seizure occurs (particular smell, ringing in the ears,
visual disturbances
• Tx: anticonvulsant meds
Hydrocephalus
• Excessive accumulation of cerebrospinal fluid (CF) in
the ventricles
• Cause- usually by a congenital defect, infection, or
tumor that obstructs the flow of CF out of the brain
• Sx- abnormally enlarged head, bulging eyes, irritability,
distended scalp veins; retardation when pressure
prevents proper development of the brain
• Tx- surgical implantation of a shunt to provide drainage
of the excess fluid (implant between the ventricles and
veins, heart, or abd. cavity)
Multiple Sclerosis (MS)
• Chronic, progressive condition resulting from degeneration
of the myelin sheath in the CNS
• Usually occurs between ages of 20 and 40
• Cause- unknown but genetics and viral infections of
immune system are suspected
• May have periods of remission
• Early Sx- visual disturbances like diplopia (double vision),
weakness, fatigue, poor coordination, numbness and
tingling
• Sx with disease progression- tremors, paralysis, speech
impairment, muscle spasms, incontinence
• * NO CURE* but treat with PT , muscle relaxants, steroids,
pysch counseling
Neuralgia
• Nerve pain
• Caused by inflammation, pressure, toxins,
disease
• Tx- directed toward eliminating cause of the
pain
Paralysis
• Usually results from a brain or spinal cord injury
• Hemiplegia- paralysis on one side of the body
(tumor, stroke, injury)
• Paraplegia- paralysis in the lower extremities or
lower part of the body ( spinal cord injury)
• Quadriplegia- paralysis of arms, legs, and body
below the spinal cord injury
• *NO CURE*, research is being directed toward
repairing spinal cord damage
• Tx: PT, OT, pysch counseling
Parkinson’s Disease
• Chronic, progressive condition involving
degeneration of brain cells
• Sx- tremors, stiffness, shuffling gait, loss of
facial expression, drooling, forward leaning
position
• *NO CURE* but meds to help with sx, PT
• Surgery can be performed to destroy a small
area of the brain and control involuntary
movements
Shingles (Herpes Zoster)
• Acute inflammation of nerve cells
• Cause- herpes virus, which also causes chicken
pox
• Occurs on one side of the body and follows a
the path of the affected nerves
• Sx- Fluid filled vesicles appear on the skin,
severe pain, redness, itching, fever
• Tx- pain meds, antiviral meds
WHO AM I ??????
• I am the basic structural unit of the nervous
system………
• I am the space between the axon of one neuron
and the dendrite of other neurons…….
• I am also known as afferent nerves……
• I am a single nerve fiber……..
• We are two main divisions of the nervous
system…..
• I can contain 12 pairs of cranial nerves and 31
pairs of spinal nerves…..
• I carry both afferent and efferent nerves…..
• We work together to maintain homeostasis…..
• I am cranial nerve # 1….. And I provide you a sense of ……..
• You would ask me to stick out my tongue and move it side
to side to test me……
• You would test me by having me read the Snellen chart…….
• I help with digestion, decrease heart rate, and the
movement of organs……
• You might give me a piece of gum to test me….
• Use a pen light to test me, have me follow
your finger…..
• Give me a hearing test to test me…….
• Give me a lemon and watch me swallow….
• I am responsible for conducting impulses
between brain parts for eye and auditory
reflexes………
• I am responsible for respiration and cardiac
regulations………
• I am responsible for posture, balance and
muscle tone and coordination………..
• I am the largest section of the brain….. And I am
responsible for………
• We cover and protect the brain and spinal cord….
There are 3 of us…..
• I am the thick outer membrane that protects the brain
and spinal cord……
• I am hollow space and the brain has four of me……
• I am a clear, colorless fluid…..
Diagnose ME……..
• I am caused by the herpes virus and cause you
a lot of pain because I am inflammed nerve
cells…….
• I weaken your muscles causing you to trip and
fall and make it difficult for you to speak and
swallow while I leave your mind intact….. Over
time you become an active mind trapped in a
paralyzed body……..
• I happen sometimes after a stroke, injury, or
tumor….. I affect one side of your body…..
• I cause your thumb, ring finger, and middle
finger to hurt, tingle and have numbness….You
may have to splint me…..
• I result from degeneration of your myelin
sheath…..
• I am caused by brain damage that leads to a
disturbance in my voluntary muscle actions…
• I cause you to have high fever, headaches,
neck pain, N/V….. I have inflammed your
meninges of your brain and spinal cord….
• You may get me if you have a brain disorder
associated with abnormal electrical impulses
in the neurons of the brain…..
• I could happen if you damage your spinal
cord…. I affect your lower extremities…..
• You might need a shunt if you have me…. I
cause an excessive accumulation of CF in the
ventricles….
• If you think I am happening give me a
thrombolytic drug within 3 hours….
• I cause you to tremor, shuffle your feet, lean
forward, and lose your facial expressions…..