The Nervous System
rev 12-12
• Receives information and produces a
meaningful, quick output.
• To do this, the nervous system
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quickly sorts through our memory bank
decides the probable meaning of the input
integrates the information
Provides a quick response
• So, the nervous system controls and
integrates all other body systems and
functions
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What are the characteristics of the nervous system
that allow us to do this?
1. It must receive information from our senses.
2. It integrates information.
-Integration is the process of taking different
pieces of information from different sources,
making sense of all of it at the same time, and
coming up with an action plan.
3. The nervous system is fast; it can do this within
tenths of a second.
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The CNS-Central Nervous System (the brain and
spinal cord)
– is the integrating and command center of the
nervous system
– It receives and interprets incoming sensory
information and produces motor responses
The PNS-peripheral nervous system is the part of
the nervous system outside the CNS.
– it contains the communication lines that link all
parts of the body to the CNS
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The Periph NS consists of
• 12 pairs of cranial nerves: carry impulses
between brain and body
• 31 pairs of spinal nerves: connect to spinal
cord via dorsal and ventral roots
– Dorsal root has sensory neurons and
transmit information TO the cord
– Ventral root has motor neurons that
transmit information FROM the cord to
the body
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• the Peripheral NS has 2 functional subdivisions
– the sensory or afferent division carries
impulses TO the CNS
• keeps the CNS informed of events going on
inside and outside of the body
– The motor or efferent division carries
impulses FROM the CNS
• this division enables us to respond to stimuli
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The Motor Division can be further subdivided into 2
parts:
• the Somatic nervous system
– Voluntary: controls voluntary and involuntary
skeletal muscle movements
• Motor neurons are activated either by
conscious control from the brain or by an
involuntary response called a reflex
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Reflex Division:
– Spinal reflexes
• Spinal reflexes are involuntary, automatic
responses handled primarily by the spinal cord
and spinal nerves
And, the other part or division of the Periph NS, the
Autonomic nervous system (ANS)
• this division regulates involuntary activities; the
activity of smooth muscles, cardiac muscles, and
glands
• Functions below the level of awareness
• (regulates anything that occurs automatically in the
body)
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• Requires 2 neurons to transmit information from the
CNS to a “target” cell
– Preganglionic neurons: cell bodies of the first
neurons lie within the CNS
• Sympathetic preganglionic fibers short
• Parasympathetic preganglionic fibers long
– The axons of these go to postganglionic neurons
which lie outside the CNS
• Postganglionic axons extend to wherever in our
body the target glands or organs are located
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The ANS is further sub-divided into the
• SYMPATHETIC NERVOUS SYSTEM which
mobilizes body systems during emergency
situations.
• Origin: thoracic or lumbar regions of the
spinal cord
• Function: releases neurotransmitter
norepinephrine for fight-or-flight reaction;
opposes parasympathetic division
• reduces blood flow to organs that do not help
with an immediate disaster
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AND the PARASYMPATHETIC
NERVOUS
SYSTEM (PSNS) which conserves our energy
and predominates during relaxing
– Origin: brain and sacral area of spinal cord
(craniosacral)
– Function: releases acetylcholine to relax the
body; opposes sympathetic division
• In most organs, the actions of the sympathetic and
parasympathetic divisions have opposite effects.
• The two divisions counterbalance each other’s
activities to maintain homeostasis.
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Composition of the Nervous System
Nerves, Neurons, Neuroglia
The Nervous System is composed of
Nerves which consists of the axons of many neurons
wrapped together in a sheath of connective tissue
Neurons are cells which are specialized for
communication.
• Classification of neurons
– Sensory or Afferent neurons carry (sensory)
information from receptors TO the CNS
– Motor (Efferent) Neurons carry messages
AWAY FROM the CNS to the muscles and
the glands
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– Interneurons or Association Neurons are
located in the CNS and conduct impulses
within the CNS. They receive information
from sensory neurons, integrate the input, and
then deliver the information to other neurons.
• are multipolar neurons
• Neuroglia (or Glia) are the supporting and
protecting cells of the nervous system. We will
speak more of these later.
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Neurons
• All neurons have
• a cell body (contains the nucleus)
• an axon (long slender tube of cell membrane;
specialized to carry electrical impulses)
– Axons of sensory neurons originate from a dendrite
– Axons of interneurons and motor neurons originate from a
cone shaped area of the cell body called the axon hillock
– At its other end, the axon branches into slender extensions
called axon terminals and the end of this is called an
axon bulb
• dendrites (typically slender extensions of the cell
body; receive stimuli)
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Types of Neurons
Unipolar Neurons have a single process which
emerges from the cell body
• this process divides into a proximal and distal
branch
– One branch behaves as an afferent branch and
the other behaves as an efferent branch
• All unipolar neurons are sensory
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Bipolar Neurons
• have 2 processes emerging from a round cell body
• processes extend from opposite sides of the cell
body
• found only in some of the special sense organs
where they act as receptor cells
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Multipolar Neurons
• have 3 or more processes
• are the most common neuron type in humans and
major neuron type in the CNS
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Interneurons or Association Neurons
• are a multipolar neuron
• located in the CNS
• conduct impulses within the CNS
• are the connecting link between sensory and motor
neurons
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Some neurons have a myelin sheath
• the myelin sheath
– is a fatty wrapping around the axon which provides
insulation to the axon and thus saves it energy
• The process of myelination continues during childhood
and is the primary reason for the increase in a child's brain
size
– it speeds impulse transmission by allowing a leaping
pattern of transmission called saltatory conduction
– The impulse jumps from one Node of Ranvier to
another
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Between neighboring Schwann cells are short,
uninsulated gaps called Nodes of Ranvier
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Figure 11.7a
PNS: Schwann Cell
Myelin sheath
CNS:
Oligodendrocyte
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Myelin
• in the peripheral nervous system is formed from
Schwann Cells which wrap around the axon
It helps damaged or severed axons of peripheral
nerves regenerate
•in the CNS is formed by oligodendrocytes
•The oligodendrocyte sheath degenerates once the
axon it protects is damaged or destroyed
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Neuroglial cells
• Provide physical support to neurons
• Protection to neurons
• Help maintain concentrations of chemicals in the
fluid surrounding them
• Neuroglial cells DO NOT generate or transmit
impulses
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Examples of Neuroglial Cells:
– Oligodendrocytes form the myelin sheath in the
CNS
– Schwann cells form the myelin sheath in the PNS
– Astrocytes anchor the neurons to nearby capillaries
– Ependymal cells are ciliated cells that move
cerebrospinal fluid around the brain and spinal cord
– Microglia are phagocytic cells for the nervous
system. They destroy microorganisms and
damaged tissues near the neurons.
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Impulse Transmission-Summary
The function of a neuron is to transmit information from one
part of the body to another.
• This is done in the form of electrical impulses.
• An impulse arrives at the dendrite
• When the impulse is strong enough, it depolarizes the
membrane and the impulse is transmitted along the axon
• When the impulse reaches the axon terminals, the
information needs to be converted to another form of
energy in order for the information to be transmitted to its
target (i.e. a muscle, a gland, or another neuron)
• A chemical, called a neurotransmitter, is released which
allows the impulse to jump the synapse, or space, between
the 2 cells
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Impulse Transmission- Definitions
• Resting or Membrane Potential: a small difference in
voltage across the cell membrane; the cell is normally
negatively charged.
– This allows the neuron to be ready to respond more quickly than it
could if it were electrically neutral.
– Think about a car battery. It retains a charge so that the
car will start as soon as the key is turned
– Unlike most body cells, neurons can alter the electrical
charge across the neurolemma. The membrane potential
alternates between -70 and +30 millivolts. Charge
differences are controlled by the movement of sodium and
potassium ions entering and leaving the neuron
• Action Potential: changes in the electrical activity of the
nerve of sufficient intensity to reach the threshold
necessary to move an electrical impulse down the axon
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• Threshold: the level of stimulus a neuron needs
in order to fire
• All or nothing phenomenon: once the threshold
level is reached, the nerve transmits an impulse
• Depolarization: moving the negative charge
within the axon closer to zero
• Na+ (sodium) moves into the cell via sodium
channels which open
• Na channels act as molecular amplifiers and
turn small electrical signals into action
potentials that can conduct for long distances
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• Repolarization: K+ (potassium) moves out of the
cell;
Na+ channels close and the reversal of the
membrane polarity triggers opening of the K+
channels so the K+ moves out of the cell. Loss of
K+ means that the interior of the axon becomes
negative again and the resting potential is restored
• Refractory period: The part of the axon that has
already fired is unable to fire again so the impulse
must move forward (This prevents the impulse
from moving backwards.)
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Nerve impulse transmission, explanation 2
• All cells demonstrate an unequal distribution of ions or a
voltage difference across the cell membrane. This is called
a MEMBRANE POTENTIAL OR A RESTING
MEMBRANE POTENTIAL. It occurs when the
membrane is not being stimulated.
• Nerve cells and muscle cells (and some cells of glands)
can produce electrochemical impulses and transmit them
along their membrane when the cell is stimulated or
“excited”.
• When a nerve cell is stimulated sufficiently, the voltage
across the membrane is changed.
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• If the stimulus is strong enough, the impulse reaches
the THRESHOLD. Once the impulse starts moving
down the axon, it is called an ACTION POTENTIAL
and follows an ALL OR NOTHING law.
• Two ions are responsible for this:
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• The sodium and potassium ion permeabilities of the
cell membrane changes.
• First, Na+ diffuses into the cell. This makes the inside
of the axon more positively charged. As the cell
becomes more positive, the THRESHOLD stimulus
level is reached. Na+ DEPOLARIZES the membrane.
• As the action potential reaches its peak, sodium
channels (or gates) close and the potassium channels
(or gates) open so K+ diffuses to the outside of the
cell. This allowing the cell to return to its original -70
mV charge or its resting potential. The Na+--K+ pump
helps to maintain this ‘normal’ charge across the cell
membrane.
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• The change of electrical current occurs in a small
portion of the cell membrane at any one time. This
allows the charge to move forward in a step-like
progression.
• Once activation of a cell has begun, the membrane is
generally insensitive to any further stimulation. This is
called the REFRACTORY PERIOD. Near the end of
the activation impulse, the cell can be activated but
only if a stimulus is much stronger than normal.
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PART II
The Brain and the Spinal Cord
rev 12-12
The CNS controls and processes all information
received by the body.
• Protection of the CNS
– Bone protects it from physical injury
– the brain is covered by the skull
– the spinal cord is surrounded by the
vertebrae
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The Brain
• The brain is the central command center of the
body
– Receives information in the form of action
potentials from various nerves and the spinal
cord, integrates it and generates the appropriate
response.
• 3 major anatomical and functional divisions of the
brain have been identified:
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Brain: Major Divisions
• Hindbrain: coordinates basic, automatic, and
vital functions
• Midbrain: helps coordinate muscle groups
and responses to sight and sound
• Forebrain: receives and integrates sensory
input from the external and internal
environment and determines most of our
complex behavior
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Hindbrain: movement and automatic functions
Medulla, Pons, Cerebellum
• Connected to the spinal cord
• Is the oldest, most primitive brain division
Medulla Oblongata: controls automatic functions of internal
organs
– cardiovascular center- regulates heart rate and
blood pressure
– respiratory center-controls rate and depth of
breathing
– other centers which coordinates reflexes such as
coughing, vomiting, swallowing, and sneezing
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– All information passing between the spinal cord
and the higher areas of the brain must pass
through the medulla
– Motor nerves from one side of the forebrain
cross over to the other side of the body in the
medulla
• Left side of brain controls right side of body
• Right side of brain controls left side of body
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• Pons
– Aids information flow
• connects the higher brain centers and the
spinal cord
• its respiratory nuclei work with the
respiratory centers of the medulla in
regulating respiration
• coordinates the information flow between
the cerebellum and higher brain centers
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Cerebellum
• Coordinates basic movements below the level
of conscious control
– Stores and produces whole sequences of skilled
movements i.e. driving
– Receives sensory input from many sources—joints,
muscles, balance and position receptors in the ear,
and visual receptors
– excessive alcohol disrupts normal functioning of
the cerebellum; this is why drunk people lose the
ability to coordinate their movements including
walking a straight line
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• The Midbrain—functions relate to vision and
hearing
– Visual and auditory sensory inputs pass through the
midbrain before being relayed to higher brain centers
– Coordinates movements of the head in response to
vision and hearing
– controls movement of the eyes and pupil size
– monitors the unconscious movement of skeletal
muscles so their actions are smooth and coordinated
• The reticular formation extends through the
medulla, the pons, and the midbrain.
– works with the cerebellum to coordinate muscle activity
to maintain posture, balance and muscle tone
– The Reticular Activating System, within the reticular
formation, is responsible for maintaining our level of
wakefulness
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The forebrain and diencephalon: emotions and
conscious thought
Important areas are the cerebrum, thalamus, hypothalamus,
and limbic system
– Also includes 2 glands: the pineal gland and the pituitary gland
• Determines our most complex behavior including emotions
and conscious thought.
Hypothalamus and Thalamus maintain homeostasis and
process information
• Hypothalamus is a small region at the base of the forebrain
that coordinates some automatic functions including
regulating homeostasis due to monitoring of sensory
signals
– Has a hunger center and a thirst center
– Also controls the pituitary gland
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• Thalamus: located just above the hypothalamus
– Is primarily a receiving, processing and transfer
center; it sends signals to the cerebrum to be
interpreted. (We become conscious of
information when it arrives at the thalamus, but
only after information arrives at the cerebrum
are we aware of which part of the body is
experiencing the information.
• Limbic System is a group of neuronal pathways which
connect parts of the thalamus, hypothalamus and cerebrum.
– involved in emotions and memory.
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• Cerebrum deals with higher functions and is
most highly developed
– is divided into left and right “cerebral
hemispheres” by the longitudinal fissure
– each hemisphere controls the opposite side of
the body
• the left hemisphere controls the right side of the body
• the right hemisphere controls the left side of the body
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– In the middle of the hemispheres is the corpus
callosum which joins the 2 hemispheres and
enables them to communicate and share
information
• Below the corpus callosum in each hemisphere
are the lateral ventricles which secrete CSF
– The outer layer of the cerebrum is called the
cerebral cortex and is primarily gray matter
– The inner portion of the cerebrum is primarily
white matter
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– surface tissue of the cerebrum is covered with
sulci (grooves) and gyri (ridges) which
increase the surface area for information
exchange
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– Each hemisphere is further divided into 4 lobes:
the frontal, parietal, temporal, and occipital
lobes
– all 4 lobes are involved in memory storage
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• The frontal lobes initiate motor activity and
are responsible for speech, conscious
thought, and personality.
• these lobes may be further divided into the
prefontal lobes or cortex (the most forward area of
these lobes) which are the intellectual center
– intelligence, motivation, personality, abstract
reasoning, judgment, planning, love, concern for
others
• the premotor cortex
– skilled repetitive activities (keyboarding/typing)
and conditioned reflexes (Pavlov’s dog)
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• the primary motor cortex which initiates
voluntary motor activity of the arms, legs,
trunk and face
• In the dominant hemisphere only is our
primary speech center
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– The parietal lobes house the somatosensory cortex
• interpret sensory information from the skin and
from proprioceptors in the muscles and joints.
– This allows us to identify the region of our
body being stimulated without looking
• Stereognosis: integrate different sensory inputs
to allow us to interpret sensory information i.e.
reaching into your pocket and being able to
interpret the coins in it without using visual
cues.
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– The occipital lobes house the primary visual
cortex and the visual association area
• association areas allow us to
interpret/understand information
– The temporal lobes interprets auditory
information and is responsible for perceptual
judgment
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Cranial Nerves
• Twelve pairs of cranial nerves arise from the brain
• They have sensory, motor, or both sensory and
motor functions
• Each nerve is identified by a number (I through
XII) and a name
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Memory: Storing and Retrieving Information
Memory has 2 stages: short term and long term
• Short term: working memory, information from previous
few hours
• Long term: information from previous days to years
The brain manages the 2 types of memory differently.
STM goes into the limbic system and triggers a burst of action
potentials so we can remember information for a few
minutes.
LTM: if information important, it is transmitted to your
cerebral cortex for storage as LTM. Neurons undergo a
permanent change and create additional synapses so we can
remember and retrieve information.
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Sleep
• Reticular activating system (RAS) controls
levels of alertness and sleep
– The neurotransmitter serotonin makes us sleepy by
inhibiting the neurons that arouse the brain
• Electroencephalograms (EEGs) allow us to study
brain function during sleep
• Stages of sleep:
– Stage 1: transitional stage between wakefulness
and sleep
– Stage 2: skeletal muscles relax, little eye or
body movement
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– Stage 3: sleep deepens, heart and respiration
slower
– Stage 4: difficult to awaken, heart and
respiration slowest, body temperature decreased
• REM (rapid eye movement) sleep: when we dream;
EEG shows level of brain activity comparable to
wakefulness
• People deprived of REM sleep become moody,
irritable and depressed and if deprived long
enough may suffer hallucinations
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Psychoactive Drugs
• Action: affects higher brain functions (consciousness,
emotions, or behavior); drugs alters the actions of brain
neurotransmitters so that neurons in the brain release an excess
of signaling molecules thus putting the brain cells into
overstimulation feelings of energy and euphoria.
• can cross the blood brain barrier
– Methamphetamine (crystal meth), cocaine, crack, alcohol,
nicotine, heroin
– When the body releases neurotransmitters, their effects are
typically short because the neurotransmitter remains in the
synapse for a brief period of time
– These drugs block the reabsorption of the neurotransmitters
so they remain in the synapse and stimulate the body again
and again
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• Dopamine is one of the most important neurotransmitters
in areas of the brain associated with pleasure
– But, as the neurotransmitter reuptake is blocked, the
body releases less and less and the “good feeling”
disappears
• Psychological dependence: user craves the feeling
associated with the drug
• Tolerance: takes more of the substance to achieve the
same affect
• Addiction: the need to continue obtaining and using a
substance; no free choice
• Withdrawal: physical symptoms that occur upon
stopping the drug
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Disorders of the Nervous System
Autoimmune Disorders:
Multiple Sclerosis (MS):
• An autoimmune disease that mainly affects young adults
– The sheaths of myelinated neurons in the brain and
spinal cord degenerate and form hardened (sclerotic)
scar tissue. These areas can’t effectively insulate the
neurons and so impulse transmission is slowed and
disrupted and the nerves are also damaged.
– People with MS experience a variety of symptoms
depending on which areas of the CNS are damaged.
• Symptoms include visual disturbances, headaches,
dizziness, weakness, loss of muscular control and
sensation, and urinary incontinence
• In advanced MS, cognitive deficits, depression
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Multiple Sclerosis
• Cause: unknown. Thought to be disorder of the immune
system or genetic tendency
– Thought that a virus attacks immune system so it
perceives myelin as a threat
• Course: can be mild to severe. Onset typically between
ages 20-40; affects more women than men
• Diagnosed: MRI, Evoked Potential nerve test to
determine the speed of impulses traveling through
nerves; examine CSF to see if any cell abnormalities
• Medications: Interferons, high doses of IV
corticosteroids or Copaxone to reduce frequency of
relapses, Avonex or Betaseran to help decrease
disability
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Amyotrophic Lateral Sclerosis (ALS) - Lou Gehrig’s
Disease
• Similar to MS; progressive neurodegenerative
disease affecting motor nerve cells in the brain and
spinal cord which control skeletal muscles. People
do not lose their ability to think—are cognitively
aware
• Average age of onset: 55 years; more common in
males
• Primary symptom is progressive weakening and
paralysis of skeletal muscles, especially those of the
arms, legs, speech, swallowing and breathing
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ALS
• Most common cause of death is respiratory failure;
people typically die within 3 years of onset
• No cure or treatment
– Only 1 FDA approved drug, Rilutek (brand name is
Riluzole); this minimally slows the disease
progression
o New medication on the market: Nuedexta
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Trauma
• Concussion: caused by a violent blow to the head or
neck
– Usually see a short loss of consciousness due to a
disruption of the electrical activity of brain
neurons.
– After regaining consciousness, person may have
blurred vision, confusion, nausea and vomiting
– New thinking—confusion may remain for period of
time because of trauma/ “shaking of brain”
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– Generally concussions don’t have permanent
damage unless there is a subdural hematoma
(bleeding into the space between the meninges)
• Bleeding increases pressure within head
(cerebral edema)squashes brain tissue and
disrupts function of brain
– Symptoms: drowsiness, headache and
weakness of 1 side of body
• Treatment: surgery for immediate relief of
pressure and repair of bleeding blood vessels
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• Signs and Symptoms
– Vary with artery affected, severity of damage
– Severe headache
– May see weakness on one side of the body, slurring of speech,
trouble speaking or trouble understanding
– Sudden confusion
– Trouble seeing or walking
– Loss of balance or coordination
• Treatment
– Endarterectomy (removal of atherosclerotic plaques)
– Anticlotting drugs or aspirin
– tPa (tissue plasminogen activator) to dissolve clot; must be
administered within 3 hours of the onset of symptoms
– Steroids to try to decrease any brain swelling
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• Spinal cord injuries: will impair sensation and function
below the level of injury
– Paraplegia or quadriplegia; can be fatal; will always
cause problems with bladder and bowel control
– May cause respiratory difficulties
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Infections: Brain and spinal cord typically do not get
infected due to the blood-brain barrier
Most body capillaries are leaky because materials diffuse into and out
of the capillaries. The cells which produce CSF are fused more tightly
and substances must pass through, not in between, the cells to get from
the blood CSF. So, microorganisms generally can’t get into CSF.
• Encephalitis: inflammation of the brain; typically
caused by a virus
– Causes: breathing in respiratory droplets,
contaminated food, insect bite, skin contact
– Symptoms: inflammation of brain tissuecerebral
edema, headache, fever, fatigue, hallucinations,
confusion, disturbances in speech, memory or
behavior, epileptic seizures
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• Treatment: Hospitalization with intravenous medications –
antiviral or antibiotics, anti-seizure to prevent seizures,
steroids to reduce brain swelling
• Acute phase usually lasts for 1-2 weeks; fever and
symptoms may gradually or suddenly disappear; some
people may take several months to recover although in
severe cases there may be residual disabilities
• Meningitis: Inflammation of the meninges; can be
viral or bacterial
– Symptoms: headache, fever, nausea and vomiting,
light sensitivity, stiff neck
– Treatment: hospitalization. If viral, mild symptoms
and will improve in few weeks
– If bacterial, can be fatal; IV antibiotics needed
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• Rabies: infectious viral brain disease
– Transmitted to humans by direct contact, either bite or lick
over broken skin
• Virus attacks the sensory neurons in the bite region then travels to
the spinal cord, then to the brain where it multiplies and kills cells
– Symptoms: swollen lymph glands, painful swallowing,
vomiting, choking, spasms of throat and chest muscles,
fever, becomes irrational. Death within 2-20 days
– Treatment:
• wash wound thoroughly ASAP, go to emergency
room or doctor, have animal tested, receive
rabies immunization ASAP
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• a regimen of one dose of rabies immune globulin
and five doses of the rabies vaccine over a 28-day
period.
– administer the rabies immune globulin and the first
dose of the vaccine as soon as possible after exposure.
Normally, additional doses of rabies vaccine follow on
days 3, 7, 14, and 28 after the first vaccination.
– Rabies immune globulin contains antibodies from
blood donors who were given rabies vaccine. The
antibodies provide interim protection until an exposed
person's own antibodies develop in response to the
vaccine.
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• injecting rabies immune globulin at the site of injury
reduces the amount of virus that is able to enter the
nerve cells and potentially initiate an active infection.
• The vaccine works by stimulating the immune system
to produce antibodies that neutralize the virus. The
person develops a protective immune response before
the virus reaches the brain and begins to actively
replicate.
• Older rabies vaccines required painful, daily
injections in the abdomen (stomach) for up to three
weeks, and they could produce severe side effects.
Current vaccines are relatively painless and are given
in your arm.
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Neural and synaptic transmission disorders: action
potentials can’t be properly sent. Symptoms depend
on which area of the brain/nerves are affected
• Epilepsy: recurring episodes of abnormal electrical
activity in brain
– Seizure triggers: fatigue, stress, flashing lights
– Seizures vary widely due to which part of brain is
affected
– Diagnosis: EEG
– Treatment: medications
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•
•
•
•
•
•
•
Things to do for person having seizure
Cushion head
Don’t try to restrain arms or legs
Loosen anything tight around neck (necktie or
scarf)
Turn on side
Nothing in mouth
Time seizure
Make note of where seizure begins and how
progresses
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• Parkinson’s disease: progressive degenerative illness;
loss of dopamine releasing neurons in the area of the
midbrain that coordinates muscle movements; can’t
perform smooth, coordinated movement
– Symptoms: stiff joints, muscle tremors (resting) in
hand, loss of mobility, depression and other mental
and cognitive (executive functioning) impairments
– Treatment: L-dopa (levodopa), a drug which the
body converts to dopamine. Will become
ineffective eventually
– Deep brain stimulation-implant an electrode deep in
the parts of the brain that control movement
– Age of onset—typically middle or late in life
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Dementia:
Is not a disease itself but is a group of symptoms
caused by various diseases or conditions
• Diagnosis made when people have 2 or more
major life functions impaired or lost
• Loss of mental functions is severe enough to
interfere with a person’s daily life
General characteristics
– decline in functioning over time; first symptom is
typically forgetfulnessmemory loss
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• Begin to see many deficit areas:
– language problem-difficulty communicating
– Difficulty with: recognizing objects
--planning, reasoning, perception
--decision making, judgment
--cognitive deficits including an inability to
manage finances, to find the way home
--loss of behavioral and emotional control
--Poor coordination
--Change in social skills
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Alzheimer’s disease is most common cause of
dementia
• Other causes-stroke, alcohol abuse, excessive drug
use, nutritional deficiencies (vit B12 deficiency),
head injury, brain tumors
• Some dementias are treatable if we can correct the
cause i.e. stop abusing alcohol, remove tumors,
correct nutritional deficiencies
• Most dementias are not reversible
• Risk factors: age, family history, smoking,
atherosclerosis, diabetes
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Alzheimer’s disease:
• disorder of mental impairment, especially memory,
due to a shortage of the neurotransmitter
acetylcholine.
– Primarily affects neurons in the limbic system and
frontal lobe. See plaques (beta amyloid) in brain tissue
and abnormal, tangled neurons. Possibly prion infection
causing misfolded proteins which then infect healthy
proteins
– Symptoms: Primarily affected are memory,
thinking and behavior. Gets worse with time.
Progresses from memory lapses to severe memory
loss, especially of STM. LTM affected more
slowly.
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–
See disorientation, behavior and personality
changes, loss of ability to function independently
• Treatment: medications which increase the brain’s
production of acetylcholine
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Brain tumors: abnormal growth in or on the brain
• Can be cancerous or benign
– Problems due to increased pressure within the
brain
– Symptoms: headache, vomiting, visual
impairment, confusion, muscle weakness,
difficulty speaking, seizures
– Treatment: Radiation and chemotherapy to try
to shrink the tumor. Surgical removal.
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