Nervous System
Allied Health Sciences I
Instructor: Melissa Lewis
Structure of the Brain:
The brain is a highly developed,
complex, and intricate mass of soft
nervous tissue.
 Is composed of a billion neurons.
 Protected by the cranium, meninges and
the cerebrospinal fluid.

Structure of the Brain
cont…
Meninges are made up of three membranous
coverings and the cerebrospinal fluid.
 Three meninges are the dura mater (outside
and lines skull on inside) arachnoid mater is
the middle layer.
 The inner layer is the pia mater and this
covers the brain surface itself and is
composed of blood vessels held together by
fine areolar connective tissue

Structure of the Brain
cont…
Cerebrospinal fluid is located between
the arachnoid and the pia mater.
 CSF is produced within the ventricles of
the brain and acts as a shock absorber
and it is a source of nutrients to the
brain.
 Brain is composed of white and gray
matter.

Structure of the Brain
cont…
The outer cortex (cerebral cortex) is
gray and it is the highest center of
reasoning and intellect.
 The brain is divided into four major
parts: the cerebrum, diencephalon,
cerebellum, and brain stem.

Structure of the Brain
cont…
The brain is the storage site for our memory.
 The storage site depends on the type of
memory. Ex: Learning how to swim or other
exercise activity would be held in the visual
area of the brain.
 The amount of memory we have on an event
depends on the time and interest spent on it
at the time. Ex: Usually traumatic events are
easy to recall.

Structure of the Brain
cont…
There are four hollow spaces or cavities
located in the brain and these are called
cerebral ventricles.
 All of the ventricles are connected with each
other and with the space under the arachniod
membrane, called the subarachniod space.
 They are filled with fluid called cerebrospinal
fluid

Structure of the Brain
cont…
This fluid circulates b/w the ventricles and
through the subarachnoid space continually.
 It serves as a shock absorber to protect the
brain and spinal cord.
 CSF carries nutrients to the brain and spinal
cord and helps remove metabolic wastes.
 CSF is produced by the choroid plexuses
which are networks of blood vessels of the pia
mater.

Cerebrum:
Cerebrum is the largest and highest section
of the brain. There is a layer of gray matter
called the cerebral cortex.
 It is divided into a R and L Hemisphere by the
longitudinal fissure.
 The outer part is arranged in folds called
convolutions and separated into two lobes
which are named from the skull bones that
surround them, Frontal, Parietal, Temporal,
and Occipital.

Cerebrum Cont…
The cerebrum is responsible for reasoning,
thought, memory, speaking, sensation, sight,
hearing, and voluntary movement.
 Frontal lobe controls the motor functions of
humans.
 Cells in the right hemisphere activate
voluntary movements that occur in the left
side of the body and vice versa.

Cerebrum Cont…
Broca’s area is located anterior to the central
fissure usually in the left hemisphere and is
associated with the ability to speak.
 If damaged one may know what to say but is
not able to.
 The area that allows us to recognize works
and interpret their meaning, spoken or read,
is located at the junction of the temporal,
parietal, and occipital lobes.

Cerebrum Cont…



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Parietal lobe compromises the sensory (somesthetic)
area.
It is found behind the fissure of Rolando in front of
the parietal lobe.
Occipital lobe houses the visual area, controlling
eyesight
Temporal lobe the upper part of the temporal lobe
contains the auditory area and the anterior part of the
lobe is occupied by the olfactory (Smell) area
The cerebral cortex also controls conscious thought,
judgment, memory, reasoning, and will power. Thus
human intelligence.
Cerebellum:
Cerebellum is the section below the back of
the cerebrum and behind the pons.
 The cerebellum consists of gray matter on the
outside and white matter on the inside.
 It is responsible for coordination of muscles,
balance and posture, and muscle tone.
 Allows each muscle to contract at the right
time, with the right strength, and for the right
amount of time so that the overall movement
is smooth and flowing.

Cerebellum cont…
The cerebellum is important when
speaking, walking, or writing.
 If injured motor impairment will result.

Diencephalon:
Diencephalon is located b/w the
cerebrum and midbrain
 Diencephalon contains Thalamus
(Directs sensory impulses) and
hypothalamus (Helps store and retain
short term memory)

Diencephalon Cont…

The hypothalamus has nine functions:
– Regulates autonomic nervous system
– Controls BP
– Helps maintain normal body temp.
– Assists in regulating the amount of food we eat
– Certain cells that respond to osmotic pressure of
the blood located within the hypothalamus
– Contracts the uterus during labor (oxytocin)
– Increases intestinal peristalsis and secretion from
intestinal glands
– Display of emotions
– Helps keep us awake when necessary
Brain Stem:

Brain stem is made up of three parts:
– Midbrain-located below cerebrum at the top of
the brain stem. It contains the nuclei for reflex
centers involved with vision and hearing.
– Pons-located in front of the cerebellum, b/w the
midbrain and the medulla oblongata. Serves as a
two-way conductive pathway for nerve impulses
b/w the cerebrum, cerebellum, and other areas of
the nervous system
– Medulla oblongata- connects w/ spinal cord.
Contains nuclei for vital functions such as the
heart rate, the rate and depth of respiration.
Spinal Cord:
Begins at the foramen magnum of the
occipital bone and continues to the second
lumbar vertebrae.
 It functions as a reflex center and as a
conduction pathway to and from the brain.
 Carries sensory (afferent) messages up to
the brain and motor (efferent) messages
from the brain to the nerves, that go up to
muscles and glands

Nerves:
Composed of bundles of nerve fibers enclosed
by connective tissue.
 If these fibers carry impulses from the sense
organs to the brain or spinal cord its called a
sensory or afferent nerve.
 If these fibers carry impulses from the brain
or spinal cord to muscles or glands its know
as a motor or efferent nerve
 If these fibers are both sensory and motor it is
referred to as a mixed nerve

Nerves Cont…
The peripheral nervous system includes all
the nerves of the body and ganglia (groups of
body cells)
 The autonomic nervous system is a
specialized part of the PNS that controls
involuntary activities of vital organs
 So, the function of the PNS is to control
automatic or involuntary activities of the body
and acts as a reflex center of the body

Nerves Cont…

Cranial Nerves are twelve pair that
begins in the brain. They are
designated by name and number; the
name may give a clue to its function
– Make table with cranial nerves I-XII

Spinal Nerves originate at the spinal
cord and go through openings in the
vertebrae. There are thirty-one pairs of
spinal nerves. All spinal nerves are
Mixed nerves.
The Autonomic Nervous
System
Autonomic Nervous System- This is an
important of the peripheral nervous system.
It helps maintain balance in the involuntary
functions of the body, but allows the body to
react in times of emergency.
 The ANS includes nerves, ganglia and
plexuses that carry impulses to all smooth
muscle, secretory glands, and heart muscle.
It regulates the activities of the visceral
organs. The activities of these organs are
usually automatic and not subject to
conscious control.

The Autonomic Nervous
System

The ANS is divided into two division:
– The parasympathetic nervous system and
the sympathetic nervous system.Usually
these two systems work together. They
maintain balanced state or homeostasis in
the body and control involuntary body
functions at proper rate.
The Sympathetic System

It consists of two cords that begin at the base of
the brain and proceed down both sides of the
spinal column. They are made up of nerve fibers
and ganglia of nerve cell bodies. They
sympathetic nerves extend to all the vital
internal organs, including the liver and
pancreas, heart, stomach, intestines, blood
vessels, the iris of the eye, sweat glands and the
bladder. It is often referred to as the “fight or
flight system”. It sends a message to the adrenal
medulla which secretes its hormones to prepare
our body for this action.
The Parasympathetic
System

It is composed of two important active nerves:
the vagus and the pelvic nerves. The vagus
nerve extends from the medulla and goes
down the neck and branches out over the
chest and neck. The pelvic nerve begins at the
spinal cord and branches out over the hip to
the lower organs of the body. Both of these
systems are influenced by emotion. They are
antagonistic of each other and therefore
maintain perfect balance.
Nerves cont…
The simplest type of nervous response is reflex. This
is an unconscious act and involuntary. Examples are
secretion of the salvia when you smell food, blinking
of an eye if a particle enters, removing your hand
from something hot as well as the movements of the
heart, stomach, and intestines.
 Every reflex is preceded by a stimulus. Any change in
the environment is called a stimulus. Example are
sounds waves, light waves and heat energy and odors.
Receptors pick up the stimuli.
 A simple reflex is one in which there is only a sensory
nerve and a motor nerve involved. A classic example
is the “knee-jerk” reflex. When the knee is tapped
with a percussion hammer the leg extends. The
muscles that respond are called effectors.

Draw & Label Nerve Cell to
Display

Axon (only one per neuron)
– Carry message away from cell body

Dendrites (multiple per neuron)
– Carry message to cell body

Myelin sheath
– Insulates axon (makes impulse move faster)

Synapse
– Space between nerve cells (where message jumps from one
neuron to another)

Stimuli, body recognizes change/stimuli, message
sent to brain, brain interprets message, brain tells
body how to respond to stimuli
Common Nervous System
Disorders
Cerebral Vascular Accident

What is CVA?

– Stroke or CVA
– Interruption of blood and O2 to brain
– Tissue death
– Third leading cause of death in the USA
Risk Factors
– Smoking
– Hypertension
– Heart disease
– Family history

Causes of CVA
– 90% caused by blood clots
– Clots lodge in carotid arteries, blocking the flow of blood to
the brain
– 10% caused by ruptured blood vessels in the brain
Cerebral Vascular Accident
Cont..


Symptoms
– Hemiplegia on opposite side of the body
– Sudden, severe headache
– Dizziness
– Sudden loss of vision in one eye
– Aphasia
– Dysphasia
– Coma
– Possible death
Treatment
– Get to the hospital immediately!!
– CT done to determine etiology
– If a clot, treatment aimed at dissolving clot
Cerebral Vascular Accident
Cont..

Prevention
– If TIAs- one aspirin a day
– Stop smoking
– Exercise and lose weight
– Control hypertension
Meningitis
Inflammation of the linings of the brain and
spinal cord. The cause may be bacterial or
viral.
 Symptoms include: headache, fever, and stiff
neck (nuchal rigidity). It can lead to
paralysis,coma,and death.
 Antibiotics are the treatment when the cause
is bacterial. As a precaution until the
physician has diagnosed the cause, antibiotics
are usually given up from due to the
seriousness of this disorder. Positive Kernig’s
and Brudinski’s signs also occur in meningitis
patients.

Paralysis

Loss of power of motion or sensation. Causes
can be trauma, disease or poisoning.
– Hemiplegia- paralysis of one side of the body.
The kinds are cerebral hemiplegia, facial
hemiplegia and spastic hemiplegia
– Paraplegia- this is the paralysis characterized by
a motor or sensory loss in the lower limbs and
trunk.
– Quadriplegia- this is a paralysis of the arms,
legs, and trunk of the body. Example: Superman
Epilepsy

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A seizure disorder of the brain, characterized by a
recurring and excessive discharge from neurons.
Epilepsy is due to the result of spontaneous,
uncontrolled, cycles of electrical activity in the neurons
of the brain. One portion of the brain stimulates
another which sets off a cycle of activity that accelerates
and runs its course until the neurons become fatigued.
A Grand Mal seizure is the most severe seizure and
occurs less frequently than the petit mal which is a
milder seizure.
In petit mal, some victims seem to be staring or
daydreaming. Medications used to control seizures are
referred to as anticonvulsants. Examples are
Phenobarbital, Dilantin, and Tegretol.
Nervous System Disorders
Cerebral Palsy- a disturbance in voluntary
muscular action due to brain damage.
Definite causes are unknown.
 Poliomyelitis- a disease of the nerve
pathways of the spinal cord which cause
paralysis.
 Hydrocephalus- a condition in which there
is an increased volume of cerebrospinal fluid
within ventricles of the brain.
 Parkinson’s Disease- is characterized by
tremors, a shuffling gait, pill-rolling
(movement of the thumb and index finger)
and muscular rigidity.

Nervous System Disorders
cont…
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Multiple Sclerosis (MS)- a chronic inflammatory
disease of the central nervous system in which
immune cells attack the myelin sheath of nerve cell
axons. The myelin sheaths are destroyed, leaving scar
tissue on the nerve cells. Diagnosis is made by the
signs and symptoms.
Dementia- a general term that includes specific
disorders such as Alzheimer’s disease, defined as a
loss in at least two areas of complex behavior, such as
language, memory, visual and spatial abilities, or
judgment that significantly interferes with a person’s
daily life.
Nervous System Disorders
cont…

Alzheimer’s Disease- a progressive disease
in which the initial symptom is usually a
problem with remembering recently learned
information.
– The nerve endings in the cerebral cortex
degenerate and block the signals that pass b/w
nerve cells.
– It’s a form of dementia. The nerve endings form a
plaque appearance. The next stage is the nerve
cells develop a build-up of abnormal fibers and
this creates neurofibrillary tangles, like a group of
telephone lines getting tangled. This cause is
unknown.
Nervous System Disorders
cont…

There are three stages:
– The first stage may last 2-4 years and involves
confusion, short-term memory loss, anxiety, and
poor judgment.
– The second stage may last 2-10 years and there is
an increase in memory loss, difficulty in
recognizing people, motor problems, logic
problems, loss of social skills.
– The third stage may last from 1-3 years and
involves the inability to recognize oneself, weight
loss, seizures, mood swings, and aphasia (loss of
speech).
Nervous System Disorders
cont…
Brain tumors may develop in any area of the
brain and the symptoms depend on which
area of the brain is affected.
 Hematoma- a localized mass of blood
collection and may occur in the spaces b/w
the meninges. Can be caused by a blow to the
head such as a subdural hematoma which
would be located b/w the dura mater and
arachnoid layer.

Disorders of the Peripheral
Nervous System


Neuritis- an inflammation of a nerve or a nerve
trunk. Causes of neuritis may be infectious, chemical,
or occur because of others conditions such as chronic
alcoholism. Treatment includes determining the
cause to eliminate the symptoms. The pain can be
treated with analgesics.
Sciatica- a form of neuritis that affects the sciatic
nerve. The pain radiates through the buttock and
behind the knee down to the foot. The person may
have difficulty walking. Treatment includes traction,
physiotherapy, exercises and possible surgery to
alleviate the symptoms.
Disorders of the Peripheral
Nervous System cont…
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Neuralgia- a sudden severe, sharp, stabbing pain
along the pathway of a nerve.
Trigeminal neuralgia- involves the fifth cranial
(trigeminal). Cause is unknown and the onset is very
rapid. The pain is severe. Treatment may be
analgesics or partial removal of the fifth cranial
nerve.
Bell’s Palsy- a condition which involves the seventh
cranial nerve (facial). The patient seems to have had a
stroke on one side of the face. It only affects
application and exercises such as whistling to prevent
atrophy. Symptoms usually disappear within a few
weeks.
Disorders of the Peripheral
Nervous System cont…
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Shingles or herpes zoster- an acute viral nerve
infection. It is usually one-sided usually on the
intercostals area. They are vesicular eruptions along
the route of the inflamed nerve. It is caused by the
same virus that causes chickenpox in children.
Treatment is analgesics and something for the itching
(pruritis).
Carpal Tunnel syndrome- the condition that
affects the median nerve and the flexor tendons that
attach to the bones of the wrist. It develops because of
repetitive movement of the wrist. Treatment consists
of immobilizing the wrist joint and/or surgery.
The End!!!