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Essentials of Human Anatomy & Physiology
Elaine N. Marieb
Seventh Edition
The Nervous System
Modified by S.Mendoza 1/2014
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Functions of the Nervous System
 Sensory input – gathering information
 Uses sensory receptors to monitor changes
(stimuli) occurring inside and outside the
body
 Integration
 To process and interpret sensory input and
decide if action is needed
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Slide 7.1a
Functions of the Nervous System
Slide 7.1b
 Motor output
 A response to integrated stimuli
 The response activates muscles or glands
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Neuroglia



“Cell Glue”
Generally assist, segregate, and
insulate neurons
Neuroglia can replicate but cannot
conduct
Nervous Tissue: Support Cells
(Neuroglia)
 Astrocytes
 Abundant, star-shaped cells
 Brace neurons
 Form barrier
between capillaries
and neurons
 Control the chemical
environment of
the brain
Figure 7.3a
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Slide 7.5
Nervous Tissue: Support Cells
 Microglia
 Spider-like phagocytes
 Dispose of debris
 Ependymal cells
 Line cavities of the
brain and spinal cord
 Circulate
cerebrospinal
fluid
Figure 7.3b, c
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Slide 7.6
Nervous Tissue: Support Cells
 Oligodendrocytes
 Produce myelin
sheath around
nerve fibers in the
central nervous
system
Figure 7.3d
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Slide 7.7a
Nervous Tissue: Support Cells
 Satellite cells
 Protect neuron cell bodies
 Schwann cells
 Form myelin sheath in the peripheral
nervous system
Figure 7.3e
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Slide 7.7b
Neurofibromatosis

Overproduction of
Schwann cells
Nervous Tissue: Neurons
 Neurons = nerve cells
 Cells specialized to transmit messages –
can conduct but cannot replicate
 Have 3 specialized characteristics
 Longevity: with nutrition, can live as long
as you do
 Amitotic: unable to reproduce
themselves (so cannot be replaced)
 High metabolic rate: require continuous
oxygen & glucose (due to lots of activity)
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Slide 7.8
Neuroglia vs. Neurons
Neuroglia divide. Neurons do not.
 Most brain tumors are “gliomas.”
 Involve the neuroglia cells, not the
neurons.
 As neuroglia grow out of control, they
press on the neurons impairing their
function
Neurolemma

Why is the plasma membrane
(neurolemma) of a neuron so
important?
 It is the site of electrical signaling –
plays a crucial role in cell to cell
interactions during development as
well
Major Regions of Neurons
 Cell body
 Contains the metabolic/biosynthetic center
of the cell (location of the nucleus)
 Does not contain centrioles (reflects
amitotic nature) but has the other
organelles
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Slide 7.8
Neuron Anatomy
 Dendrites
 hundreds per cell –
diffusely branched
– close to cell body
 Receptive sites
conduct impulses
toward the cell
body
 Immense surface
area for reception
Figure 7.4a
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Slide 7.10
Neuron Anatomy
 Axons
 Transmit
impulses away
from cell body
 Vary in length
and diameter
 Larger diameter
= faster
conduction
Figure 7.4a
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Slide 7.10
Neuron Anatomy
 Axons
 Axon collaterals
– right angle
branches
connecting other
neurons
 Axon terminals
located at end of
axon branches
Figure 7.4a
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Slide 7.10
Axon terminals
 Contain vesicles with
neurotransmitters –
chemicals which
transmit electrical
impulses
 Axonal terminals are
separated from the next
neuron or effector by
the Synaptic cleft
 Synapse -junction between
nerves
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Slide 7.11
Myelin Sheath
 Function:
 Protects & insulates
fibers
 Increases speed of
transmission
 Formed by Schwann
Cells (add to notes)
Figure 7.5
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Slide 7.12
Functional Classification of
Neurons
 Sensory (afferent)
 Nerve fibers that carry information from
sensory receptors to the central nervous
system (CNS)
 Ends of dendrites associated with
specialized receptors – know examples in
your notes!
Figure 7.1
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Sensory Receptors
Ends of dendrites are associated
with specialized receptors
Cutaneous receptors: pressure,
pain, heat, cold
Proprioceptors: muscles &
tendons: amount of stretch or
tension
Specialized receptors in sense
organs: sight, hearing, smell,
taste, equilibrium
Functional Classification
 Motor (efferent) division
 Nerve fibers that carry impulses from the
central nervous system to muscles &
glands
Figure 7.1
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Slide 7.3b
Functional Classification
Association or Interneurons
• Responsible for integration & reflex –
connect motor & sensory neurons
• Make up over 99% of neurons
Structural Classification of Neurons:
ADD TO NOTES!
 Multipolar neurons – many extensions
from the cell body
Figure 7.8a
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Slide 7.16a
Structural Classification of Neurons
 Bipolar neurons – one axon and one
dendrite
Figure 7.8b
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Slide 7.16b
Structural Classification of Neurons
 Unipolar neurons – have a short single
process leaving the cell body
Figure 7.8c
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Slide 7.16c
Functional Properties of Neurons
Two major functional properties
of neurons resulting in
electrochemical event
Irritability - ability to respond to
stimuli & convert it into a nerve
impulse
Conductivity – ability to transmit an
impulse to other neurons, muscles,
or glands
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Slide 7.17
Synapse – know the diagram
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Slide 7.11
Stages of the Chemical Event
 The action potential (electrical signal)
reaches the axon terminals
 Neurotransmitter is released into the synaptic
cleft when the vesicle fuses with the
membrane (presynaptic neuron)
 NT diffuses across the cleft and binds to the
receptors on the dendrite of the next neuron
(postsynaptic neuron)
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Slide 7.21
Stages of the Chemical Event
 An action potential is started in the next
neuron (or muscle or gland)
 In order to prevent continuous stimulation, NT
is removed from the synapse through:
 Re-uptake
 Enzymatic breakdown
 Synapse Animation
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Slide 7.21
Development Aspects of the
Nervous System
 As you learn:
Axon terminal gets wider so
more NT can be released (more
surface area)
Synaptic cleft get narrower
More NT gets across to
receptors
Faster & more efficient process
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Slide
Reflex Activity – page 438
 Reflex: rapid predictable motor
response to stimuli that the body is
programmed to do
Unlearned, unpremeditated,
involuntary
 Withdrawal from pain
Learned or acquired reflexes result
from repetition or practice.
 Example: experienced driver drives a car
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Slide 7.58
Reflex Activity
 Two types:
Autonomic: regulate the activity of
smooth muscles, the heart, and
glands
Examples: salivary reflex, pupilary
reflex, digestion, blood pressure
Somatic reflexes: skeletal muscle
reflexes
Example: knee jerk reflex
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Slide 7.58
Reflex – define 5 elements of
Know your diagram
The Reflex Arc
 Reflex – rapid, predictable, and
involuntary responses to stimuli
 Reflex arc – direct route from a sensory
neuron, to an interneuron, to an effector
Figure 7.11a
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Slide 7.23
Simple Reflex Arc
Figure 7.11b, c
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Slide 7.24
Regeneration
 Mature neurons are incapable of
mitosis. However, PNS axons can
regenerate if cell body is not destroyed.
 The uninjured cell body gets larger in
order to synthesize proteins needed for
regeneration
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Slide
7.14b
Regeneration
 Axons regenerate at a rate of 1.5 mm/day
 The greater the distance between severed
nerve endings, the less chance of
recovery. Axonal sprouts may grow into
surrounding areas and form a mass called
a neuroma.
 Surgical realignment can help. Retraining
may be necessary once the connection is
completed
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Slide
7.14b
Regeneration
 PNS vs CNS
In PNS axon regeneration,
macrophages clean out the debris
from the injury.
Schwann cells will form a tunnel of
neurolemma to guide severed nerve
ending together. A growth factor is
also released
In CNS – No Schwann cells to do this.Slide
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7.14b
Organization of Nervous System
Memorize the info on the chart provided you need to understand how it all fits
together
Classification of the Nervous System
 Central nervous system (CNS)
 Brain & Spinal cord
 Integrative & control centers
 Peripheral nervous system (PNS)
 Cranial & Spinal Nerves (outside the brain
and spinal cord)
 Communication lines between the CNS and
the rest of the body
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Slide 7.2
Distribution of Cranial Nerves
Figure 7.21
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Slide 7.59
Spinal Nerves
Figure 7.22a
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Slide 7.64
Functional Classification of the
Peripheral Nervous System
 Motor (efferent) division
 Two subdivisions
 Somatic nervous system = voluntary
Conducts impulses to skeletal
muscles
 Autonomic nervous system = involuntary
Conducts impulses to cardiac muscle,
smooth muscle, & glands
Figure 7.1
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Slide 7.3c
Functional Classification of the
Peripheral Nervous System
 Autonomic nervous system
 Has 2 subdivisions
 Sympathetic division
Fight or flight system
Speeds up HR, respiration rate,
increases cardiac output, deactivates
digestive system
 Parasympathetic division
Resting system
Activates digestive, slows other
systems
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Organization of the Nervous
System
Figure 7.2
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Slide 7.4
Central Nervous
System
Protection of the CNS
 Scalp, hair, and skin- Cushions
 Bone: Skull and vertebral column
– Surrounds & Protects
 Meninges – membranes fig 7.16
Figure 7.16a
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Meninges
 Epidural space:
 Found around spine only-contains fat
& CT
 Dura mater – “tough mother”
 Double-layered external covering
fused together except where dural
sinuses are enclosed
 Dural sinuses – venous blood
collected from brain and shunted into
internal jugular vein
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Slide
7.45a
Meninges
 Subdural space
Contains serous fluid
 Arachnoid layer
 Middle layer
 Spider web-like
 Subarachnoid space
 Contains CSF & major arteries &
veins
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Slide
7.45b
Meninges
 Pia mater:
“little mother”
 Internal layer
of delicate CT
 Clings directly
to the surface
of the brain
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Slide
7.45b
Blood Brain Barrier
 Function: ensures
stable environment by
endothelial tight
junctions(the least
permeable capillaries
of the body)
 Excludes many
potentially harmful
substances and
metabolic waste
products
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Slide 7.48
Blood Brain Barrier
 Useless against some substances
 Fats and fat soluble molecules
 Respiratory gases
 Alcohol
 Nicotine
 Anesthesia
 Medical Implication (add to notes):
Hard to get antibiotics through BBB
so hard to treat brain infections
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Slide 7.48
Blood Brain Barrier
 Not identical in all regions
In the hypothalamus region, the
BBB is almost non-existent so
chemical composition of blood
can be monitored
 Different in newborns vs. adult
 Kernicterus: description on next
page
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Slide 7.48
Kernicterus – copy BLUE into notes
Hemoglobin is released into blood as RBC’s
recycle
Hemoglobin breaks down into bilirubin which is
normally cleared from the body by the liver
Newborns have an immature liver so bilirubin
will build up and cause jaundice of body and
of brain
Infant will have diminished reflexes, lethargy,
reduced muscle tone, and a high pitched
abnormal cry as external symptoms.
UV light treatment
helps dissolve
excess bilirubin.
Cerebrospinal Fluid
 Function:
Support, protect, & exchange of
materials
Forms a watery cushion to
protect the brain
Circulates to monitor levels of
CO2, O2 , pH – triggers feedback
mechanism if necessary
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Slide 7.46
Cerebrospinal Fluid
 Similar to blood plasma
composition
 Location: subarachnoid space and
4 ventricles in brain and central
canal of SC
 Formed by the choroid plexus
(network of capillaries) in brain
ventricles: seeps from capillaries
into ventricles
 ~800 ml formed daily
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Slide 7.46
Circulation of CSF: Memorize
Choroid plexus  lateral (1st & 2nd) ventricles
 interventricular foramen  3rd ventricle
 cerebral aqueduct  4th ventricle 
subarachnoid space & central canal of SC
Hydrocephalus
•Define: something blocks
Slide 7.47b
circulation/drainage of CSF, fluid
accumulates & puts pressure on brain
•Adult:skull bones are fused, fluid
compresses BV and soft brain tissue – result
is brain damage
•Child:skull bones not fused, head may
enlarge, brain damage still a possibility
•Treatment: insert a shunt to go around
blockage
Figure 7.17b
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Hydrocephalus
Do not need to copy this info
Shunt drains excess fluid
from ventricles into
abdominal cavity
where body can
reabsorb it.
Pressure then does not
build up in the brain
Brain Development (CNS)
 CNS develops from the embryonic
neural tube
 The neural tube becomes the brain
and spinal cord
 The opening of the neural tube
becomes the 4 ventricles
 Malformations of neural tube lead to
several defects such as spina bifida
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Major Regions of the Brain
 Cerebral
hemisphere
 Diencephalon
 Brain stem
 Cerebellum
Figure 7.12
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Slide 7.27
INTERESTING FACT OR MYTH
ABOUT THE BRAIN?
Your Brain, on average, weighs 3 pounds.
Your skin weighs twice as much as your
brain.
The brain is made up of 75% water.
There are between 1,000 – 10, 000 synapses
for each neuron.
There are no pain receptors in the brain, so the
brain can feel no pain.
-
While an elephant’s brain is physically larger than a
human brain, the human brain is 2% of total body
weight (compared to 0.15 % of an elephant’s brain),
meaning humans have the largest brain to body size.
- There are 100, 000 miles of blood vessels in the brain.
-
The human brain is the fattest organ in the body and
may consists of at least 60% fat.
- Neurons develop at the rate of 250,000 neurons per
minute during early pregnancy.
Your brain stops growing at age 18
The first sense to develop while in utero is the
sense of touch
- Children who learn two languages before the
age of five alters the brain structure and
adults have a much denser gray matter.
- Your brain uses 20% of the total oxygen in
your body.
- If your brain loses blood for 8 to 10 seconds,
you will lose consciousness.
- Information can be processed as slowly as
0.5 meters/sec or as fast as 120 M/S (about
268 miles/hr).
- While awake, your brain generates between
10 – 23 watts of power–or enough energy
to power a light bulb.
- The brain can live for 4 to 6 minutes without oxygen,
and then it begins to die. No oxygen for 5 to 10
minutes will result in permanent brain damage.
- The next time you get a fever, keep in mind that the
highest human body temperature ever recorded was
115.7 degrees–and the man survived.
- Excessive stress has shown to "alter brain cells, brain
structure and brain function."
Cerebrum
 The
surface is
made of
ridges
(gyri) and
grooves
(sulci)
 Purpose:
triple
surface
area
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Slide
7.28b
Figure 7.13a
Lobes of the Cerebrum
 Fissures (deep sulci) divide the
cerebrum into lobes
Longitudinal fissure: separates
2 hemispheres
Transverse fissure: separates
cerebellum
Lateral fissure:on side of brain
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Lobes of the Cerebrum
 Fissures (deep grooves) divide the
cerebrum into lobes
 Surface lobes of the cerebrum
 Frontal lobe
 Parietal lobe
 Occipital lobe
 Temporal lobe
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Slide 7.29a
Lobes of Brain
Surface lobes of the cerebrum
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
Lobes of the Cerebrum
Figure 7.15a
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Slide
7.29b
The Cerebrum
 Cerebral cortex:
 Gray matter: cell bodies
 1/16” thick, ~40% of brain mass
 Voluntary motion
 Higher order thinking skills
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Slide 7.30
Sensory and Motor Areas of the
Cerebral Cortex
Figure 7.14
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Slide 7.31
Specialized Areas of the Cerebrum
 Somatic sensory area – receives
impulses from the body’s sensory
receptors
 Primary motor area – sends impulses to
skeletal muscles
 Broca’s area – involved in our ability to
speak
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Slide 7.30
Specialized Area of the Cerebrum
 Cerebral areas involved in special
senses
 Gustatory area (taste)
 Visual area
 Auditory area
 Olfactory area
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Slide 7.32a
Specialized Area of the Cerebrum
 Interpretation areas of the cerebrum
 Speech/language region
 Language comprehension region
 General interpretation area
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Slide 7.32b
Layers of the Cerebrum
 White matter
 Fiber tracts
inside the
gray matter
 Example:
corpus
callosum
connects
hemispheres
& allows
them to
communicate
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Figure 7.13a
Slide
7.33b
Layers of the Cerebrum
 Basal nuclei – internal islands of
gray matter w/in white matter
 Indirectly helps initiate and
control slow stereotyped muscle
movement
 When impaired, postural
disturbances, muscle tremors
uncontrolled contractions result
Figure 7.13a
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Slide
7.33c
Cerebral Nuclei
Diencephalon
 Sits on top of the brain stem
 Enclosed by the cerebral
hemispheres
 Made of three parts
 Thalamus
 Hypothalamus
 Epithalamus
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Slide
7.34a
Thalamus
 Surrounds the third ventricle
 The relay station for sensory impulses
 Transfers impulses to the correct part of
the cortex for localization and
interpretation
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Slide 7.35
Hypothalamus
 Under the thalamus
 Important autonomic nervous system
center
 Helps regulate body temperature
 Controls water balance
 Regulates metabolism
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Slide 7.36a
Hypothalamus
 An important part of the limbic system
(emotions)
 The pituitary gland is attached to the
hypothalamus
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Slide 7.36b
Epithalamus
 Forms the roof of the third ventricle
 Houses the pineal body (an endocrine
gland)
 Includes the choroid plexus – forms
cerebrospinal fluid
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Slide 7.37
Brain Stem
 Attaches to the spinal cord
 Rigidly programmed
automatic behaviors
necessary for survival
 Parts of the brain stem
 Midbrain
 Pons
 Medulla oblongata - If
damaged severely, death
will result
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Slide
7.38a
Midbrain
 Mostly composed of tracts of nerve
fibers
 Has two bulging fiber tracts –
cerebral peduncles
 Has four rounded protrusions –
corpora quadrigemina
 Reflex centers for vision and hearing
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Slide 7.39
Pons
 The bulging center part of the brain
stem
 Mostly composed of fiber tracts
 Includes nuclei involved in the control of
breathing
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Slide 7.40
Medulla Oblongata




The lowest part of the brain stem
Merges into the spinal cord
Includes important fiber tracts
Contains important control centers
 Heart rate control
 Blood pressure regulation
 Breathing
 Swallowing
 Vomiting
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Slide 7.41
Reticular Formation
 Diffuse mass of gray matter along the
brain stem
 Involved in motor control of visceral
organs
 Reticular activating system plays a role
in awake/sleep cycles and
consciousness
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Slide 7.42a
Reticular Formation
Figure 7.15b
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Slide 7.42b
Cerebellum
 Two hemispheres with convoluted
surfaces
 Provides involuntary smooth,
coordinated body movements
 Likened to the control system of an
automatic pilot to constantly
monitor and adjust muscle
functioning
 Ataxia
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Slide
7.43a
Cerebellum
Figure 7.15a
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Slide 7.43b
Brain Disorders
You need to have a basic description &
understanding of the following disorders –
so read everything but copy down every
blue detail
Hemispherectomy to control seizures
Developmental Aspects of the
Nervous System
Cerebral palsy
Lack of oxygen to
developing (in utero)
infant
May be caused by:
mother who smokes,
mother who gets
German measles,
problems during labor
& delivery, etc.
Cerebral palsy
symptoms
Alzheimer’s Disease
 Progressive degenerative brain
disease
 Mostly seen in the elderly, but may
begin in middle age(early onset)
 Structural changes in the brain
include abnormal protein deposits
(plaques) and twisted fibers within
neurons
 Victims experience memory loss,
irritability, confusion and ultimately,
hallucinations and death
Parkinson’s disease
Age 50s to 60s
Degeneration of dopamine releasing neurons
in nuclei of brain stem – cause is unknown
Tremors, stiff facial expression, slow in
movement
Treatment: L-dopa, deep brain stimulation
through implanted electrodes
Huntington’s chorea
Dominant genetic disorder
Degeneration of basal nuclei and cerebral
cortex
Strikes during middle age – usually fatal
within 15 years
Wild, jerky motions
Treated with drugs that block dopamine but
no cure
Disorders
 Meningitis
Inflammation of the meninges
Can be bacterial or viral
Bacterial is worse due to the
toxins excreted by bacteria
 Encephalitis
 Brain inflammation
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Slide
7.45b
Traumatic Brain Injuries
 Cerebral edema
 Swelling from the inflammatory
response
 May compress and kill brain tissue
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Slide 7.49
Traumatic Brain Injuries
 Concussion
 Slight brain injury
 No permanent brain damage
 Contusion
 Nervous tissue destruction occurs
 Nervous tissue does not regenerate
 Cerebral edema
 Swelling from the inflammatory response
 May compress and kill brain tissue
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 7.49
Cerebrovascular Accident (CVA)
 Commonly called a stroke
 The result of a ruptured blood vessel
or a clot in a BV supplying a region of
the brain
 Ischemia: Tissue death – lack of 02 Brain tissue supplied with oxygen
from that blood source dies
 Loss of some functions or death may
result
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 7.50
CVA
TIA
Transient ischemic
attacks
Last from 5-50 minutes
Symptoms: numbness,
temporary paralysis,
impaired speech
Not permanent BUT
warning sign of
impending stroke
Multiple sclerosis
Demyelinating disorder – form scleroses
(hardened deposits)
Autoimmune
Onset 20-40 years of age –more common in
women
Incurable – treatments based on slowing
progression
Multiple sclerosis
Disorders
Hemiplegia
Paralysis of left or right side of body – due to
brain injury/stroke rather than spinal cord injury
Spinal Cord
Approximately 17 inches long and extends
from the foramen magnum to the 1st/2nd
lumbar vertebrae.
It is about the size (diameter) of your thumb
for most of its length
Meningeal coverings extend to the 4th sacral
vertebrae
Spinal Cord
Lumbar puncture aka spinal tap
Purpose: to obtain a CSF sample for testing
Location: level of L4 or L5 - since spinal
cord ends at L1 or L2 – this reduces the
chance of puncturing the spinal cord
Patient must remain lying down for 6-12
hours since withdrawal of fluid decreases
internal pressure which may cause an
excruciating headache until body regulates
itself.
Lumbar (spinal) tap
Terms to Know
Flaccid paralysis – No voluntary muscle
motion possible – muscles will atrophy
Spastic paralysis – affected muscles stay
healthy due to reflex activity but motions
are involuntary and uncontrolled
Terms to Know
Quadriplegic: all four limbs are affected
Paraplegic: only the legs are affected
Spina Bifida
Spina bifida-incomplete formation of
vertebrae – folic acid reduces risk
Occulta-no external manifestations
Cystica-saclike cyst protrudes from spine
Meningocele-cyst contains meninges & CSF
Myelomeningocele-cyst also contains portions of
spinal cord and nerve roots
Spina Bifida Types
Milder forms of SB
Occulta
Cystica
Spina Bifida
Myelomeningocele
Fetal Surgery
Study proves
benefits of spina
bifida surgery
(02/10/11)