THE
NERVOUS
SYSTEM
Functions of the Nervous System
 Sensory input – gathering information
 To monitor changes occurring inside and outside
the body
 Changes = stimuli
 Integration
 To process and interpret sensory input and decide if
action is needed
 Motor output
 A response to integrated stimuli
 The response activates muscles or glands
Structural Classification of the
Nervous System
 Central nervous system
(CNS)
 Brain
 Spinal cord
 Peripheral nervous system
(PNS)
 Nerve tissue outside the brain
and spinal cord
Structural Classification of the
Peripheral Nervous System
 Sensory (afferent) division
 Nerve fibers that carry information to the
central nervous system
 Motor (efferent) division
 Nerve fibers that carry impulses away from
the central nervous system
Motor (efferent) division
Two subdivisions
1. Somatic nervous system = voluntary
2. Autonomic nervous system = involuntary


Sympathetic nervous system - functioning
 “fight-or-flight”
 Response to unusual stimulus
 Takes over to increase activities
 Remember as the “E” division = exercise,
excitement, emergency, and embarrassment
Parasympathetic nervous system - functioning
 Housekeeping activities
 Conserves energy
 Maintains daily necessary body functions
 Remember as the “D” division - digestion,
defecation, and diuresis (urination)
Structural Classification of
the Nervous System
Organization of the Nervous System
Nervous Tissue – Neurons
Neurons = nerve cells
 Cells specialized to
transmit messages
Major Regions of Neurons
 Major regions of neurons
 Cell body – nucleus and metabolic center of
the cell
 Processes – fibers that extend from the cell
body
 Dendrites – conduct impulses toward the
cell body
Major Regions of Neurons
 Axons – conduct impulses away
from the cell body
 Axons end in axonal terminals
 Axonal terminals contain vesicles with
neurotransmitters
 Axonal terminals are separated from the
next neuron by a gap
 Synaptic cleft – gap between adjacent neurons
 Synapse – junction between nerves
Major Regions of Neurons
 Schwann cells – produce myelin sheaths
in jelly-roll like fashion
 Nodes of Ranvier – gaps in myelin
sheath along the axon
Functional Classifications of
Neurons
 Sensory (afferent) neurons
 Carry impulses from the sensory receptors
 Cutaneous sense organs
 Proprioceptors – detect stretch or tension
 Motor (efferent) neurons
 Carry impulses from the central nervous system
 Interneurons (association neurons)
 Found in neural pathways in the central nervous
system
 Connect sensory and motor neurons
The Reflex Arc
 Reflex – rapid, predictable, and
involuntary responses to stimuli
 Reflex arc – direct route from a (receptor)
sensory neuron, to an interneuron, to a
motor neuron, (to an effector)
Types of Reflexes and Regulation
 Autonomic reflexes




Smooth muscle regulation
Heart and blood pressure regulation
Regulation of glands
Digestive system regulation
 Somatic reflexes
 Activation of skeletal muscles
Human Reflex Physiology
http://www.youtube.com/watch?v=HfuhVWK8C0U
Human Reflex Physiology
Do the lab activity here
Functions in Motor Neurons
 Efferent neurons go to the muscle fibers
(motor neurons)
 Neuron : muscle fiber ratio
 1:10 fibers in delicate, precise movements
(eye muscles)
 1:340 fibers in finger muscles
 1:1800 fibers in gastroc muscles
 1:2,000-3,000 fibers in largest muscles
 Neurons can facilitate - set off an
excitatory response
 neurons can inhibit – a muscle
does not fully contract all fibers
at the same time.
 Inhibitory inhibition reduces input of
unwanted stimuli (like the touch of
clothing) and allows for smooth,
purposeful responses
 intense concentration may have an effect
on decreasing the inhibitory influences
increasing the full activation of muscle
fibers
 this may increase muscle strength
without increasing muscle size
Twitch characteristics –
 how muscle fibers respond
 motor units respond with high
or low tension
FAST TWITCH MUSCLE FIBERS
large motor neurons
fast conduction velocity
high force
quickly reaches peck tension
fatigues quickly
many developed in weight lifters
SLOW TWITCH MUSCLE FIBERS
small motor neurons
slow conduction velocity
low force
slow to reach tension
fatigue resistant
many developed in runners
 actions cause a blend of fast and slow
twitch motor units responding
 when more force is needed – larger
axons are recruited which stimulates
more fast twitch fibers
 when endurance is needed – smaller
axons are recruited which stimulates
more slow twitch fibers
 motor unit firing pattern varies in types of
athletes
 weight lifters recruit many units
simultaneously (mostly fast twitch)
 endurance athletes have asynchronous
pattern (mostly slow twitch) and some fire
while others recover
 with prolonged aerobic training, fast
twitch muscle fibers can become more
fatigue resistant
FAST TWITCH MUSCLE FIBERS
http://www.youtube.com/watch?v=R7dCi1rOMq4
http://www.youtube.com/watch?v=co9NjWkrLII
Types of muscle fiber fatigue
1. nutrient fatigue – reduction of muscular
glycogen, but enough oxygen – usually
from prolonged sub-maximal exercise
2. short-term maximal exercise fatigue –
associated with lack of oxygen (sprint)
3. neural fatigue – no transmission from
neuron to muscle fiber – neuron
transmission reduces after high motor unit
recruitment (max out in weight lifting)
RECEPTORS IN MUSCLES
AND TENDONS
(PROPRIOCEPTION)
Proprioceptors monitor stretch,
tension, pressure, and relay
information to the conscious and
unconscious areas of the CNS
for processing so that you can
modify muscle activity.
Muscle Spindles:
 provide information about length and
tension of a muscle
 they are located in the muscle and are
parallel to the fibers
 there are more spindles in muscles that
perform complex actions
 they are active in postural muscles to
counter the pull of gravity
Hold a book with your eyes
closed – you are able to
maintain the elbow at 90
spindles – to sensory neurons (afferent) – to SC –
to motor (efferent) neurons - to the muscle fibers
(modify movement or posture)
Muscle Spindles:
http://www.youtube.com/watch?v=F871bBWS4oY
Golgi Tendon Organs:
 located in the tendons, in series with the
muscles
 these detect tension, not length, in the muscle
 increased tension or stretch in the muscle
causes inhibitory responses in the stretched
muscle
 this protects the muscle and connective tissue
from injury due to excessive loading
 this also helps maintain constant tension while
holding a paper cup
Golgi Tendon Organs:
http://www.youtube.com/watch?v=7T4NI_2qDEM
Regions of the Brain
Regions of the Brain
 Cerebral hemispheres
(cerebrum)
 Diencephalon
 Brain stem
 Cerebellum
Cerebral Cortex
(cerebrum)
 Contains sensory and motor
centers
 Contains areas for memory,
learning and thought
Cerebrum
 Paired (left and right)
superior parts of the
brain
 Include more than half
of the brain mass
 The surface is made of
ridges (gyri) and
grooves (sulci)
 Fissures (deep
grooves) divide the
cerebrum into lobes
Are you right brained or left
brained?
The Right Brain vs Left Brain test ... do you
see the dancer turning clockwise or
counter-clockwise?
http://www.news.com.au/heraldsun/story/0,
21985,22556281-661,00.html
RIGHT BRAIN FUNCTIONS
(clockwise direction)
uses feeling
"big picture" oriented
imagination rules
symbols and images
present and future
philosophy & religion
can "get it" (i.e. meaning)
believes
appreciates
spatial perception
knows object function
fantasy based
presents possibilities
impetuous
risk taking
LEFT BRAIN FUNCTIONS
(counter-clockwise direction)
uses logic
detail oriented
facts rule
words and language
present and past
math and science
can comprehend
knowing
acknowledges
order/pattern perception
knows object name
reality based
forms strategies
practical
safe
Surface lobes of the cerebrum
 Frontal lobe
 Parietal lobe
 Occipital lobe
 Temporal lobe
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
Cerebral areas involved in special
senses

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Gustatory area (taste)
Visual area
Auditory area
Olfactory area
Interpretation areas of the cerebrum
 Speech/language region
Diencephalon
 Sits on top of the brain stem
 Regulates autonomic nervous
functions:
 Body temperature
 Blood pressure
 Sleep
 Emotions
 Made up of:
 Thalamus
 Hypothalamus
 Epithalamiums
Brain Stem
 Attaches to the spinal cord
 Bridge between hemispheres, provides
interconnections between the spinal cord,
cerebrum, and cerebellum
 Made up of
 Midbrain
 Pons
 Medulla oblongata
 Controls
 Breathing, heartbeat,
blood flow, cough
Cerebellum
 An intricate feedback system that
coordinates body movements
 This system compares, evaluates,
integrates body motions, makes postural
adjustments, maintains equilibrium, and
perceives speed of body motion
Take a look at the sheep brain
CEREBRAL CORTEX
(conscious experience, perception, and
planning)
input
↓
CEREBELLUM
↑
input
BRAIN STEM AND SPINAL CORD
(body positioning and proprioception)
The cerebellum has two
informational pathways:

data enters from all different brain areas
and contains memory cells

one originates from the brain stem and
interacts with pathways to learn new
patterns of movement based on current
information
Some scientists believe that mental
activities may be coordinated in the
cerebellum the same way motor
activities are coordinated.
The cerebellum uses constant
proprioceptive information
(feedback on body positioning)
to fine-tune motor movements.
The cerebellum contains more
neurons than any other part of
the brain and can process
information faster than any other
part of the brain.
Cerebellar dysfunction results in
problems walking, balance, and
accurate hand and arm
movement
Cerebellar function is important for
language processing and
selective attention. It may be
associated with dyslexia and
autism.
Lesions in the cerebellum result in
“dysmetria” – an overshooting when
reaching for a target.
Patients may not be able to perform rapid
alternating movements.
Specific areas of the cerebellum result in
specific symptoms.
Cerebellar Dysfunction
 http://www.youtube.com/watch?v=jx9Eq6Jxg9s
 http://www.youtube.com/watch?v=eBvzFkcvScg&f
eature=player_embedded
 http://www.youtube.com/watch?v=jnQcKAYNuyk
 http://www.youtube.com/watch?v=xLlL24shW7E
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
Cerebral edema. There is midline
shift towards the left (short arrow).
Normal left basal ganglia (long
arrow).
Cerebral hemorrhage
 The rupture of a blood vessel
supplying blood to a region of
the brain
Neurological Disorders
Cerebrovascular Accident
(CVA)
 Commonly called a stroke
 The result of a ruptured blood vessel
supplying a region of the brain
 Brain tissue supplied with oxygen
from that blood source dies Loss of
some functions
 or death may result
Alzheimer’s Disease
 Progressive degenerative brain
disease
 Mostly seen in the elderly, but may
begin in middle age
 Structural changes in the brain include
abnormal protein deposits and twisted
fibers within neurons
 Victims experience memory loss,
irritability, confusion and ultimately,
hallucinations and death
An Alzheimer Brain
Parkinson’s Disease
1. the chemical, dopamine, allows smooth,
coordinated function of the body's
muscles and movement
2. dopamine-producing cells are damaged
3. usually strikes people in their 50’s
4. symptoms include
 tremor (shaking)
 slowness of movement
 rigidity (stiffness)
 difficulty with balance
Huntington’s Disease
 a genetic disorder of middle age
 initial symptoms are wild, jerky, and
flapping movements called “chorea”
 later symptoms are a marked mental
deterioration
 usually fatal within 15 years of
diagnosis
Multiple Sclerosis
 is usually diagnosed in a person in their
20’s
 thought to be an autoimmune disease of
the CNS
 myelin sheaths are destroyed and
replaced by scar tissue
 this disrupts the neuron’s ability to
conduct impulses
 symptoms include
Multiple Sclerosis
 symptoms include
 Changes in Cognitive Function, including problems
with memory, attention, and problem-solving
 Dizziness and Vertigo
 Emotional Problems and/or Depression
 Fatigue (also called MS lassitude)
 Difficulty in Walking and/or Balance or Coordination
Problems
 Abnormal sensations such as Numbness or “pins
and needles”
 Pain, spasticity, vision problems
Neurological Diagnostics
EEG –
Electroencephalogram
 Patterns of electrical activity of the neurons
(brain waves)
 Brain waves are as unique as fingerprints
 Wide awake waves are different from
relaxation or sleep waves
 Abnormal brain waves are seen in patients in
comas, with seizures, or drug overdoses
 Flat EEG (absence of waves) means clinical
death or being “brain dead”
Electroencephalogram
Cerebral Angiogram
 Dye into the blood stream and then xrayed
 Allows assessment of the blood supply to
the brain (carotid arteries) and cerebral
arteries
 Allows you to see narrowing of the
arteries
Cerebral Angiogram
Cerebral angiogram shows the aneurysm
(arrows) that was responsible for the bleed.
CAT scan
Computerized Axial Tomography
 A powerful x-ray
 Shows soft tissue as well as bone
CAT scan
Computerized Axial Tomography
MRI
Magnetic Resonance
Imaging
 Magnetism causes alignment of water
molecules
 This allows imaging of body tissues by
density
MRI
Magnetic Resonance
Imaging
PET scan
 High energy gamma rays
 Monitors biochemical activity – can
detect any metabolic abnormalities
PET scan
Spinal Cord
Injuries
Spinal Shock – any sever injury to
the spinal cord that produces a
short period of sensory and
motor paralysis



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Skeletal muscles are flaccid
No somatic or visceral reflexes
No sensations of touch, pain, heat, cold
Length of shock depends upon the
severity of the injury
Spinal concussion – caused by
violent jolts near the spinal cord,
no visual damage to the spinal
cord
 Short period of spinal shock
 Temporary symptoms but usually
complete recovery in hours
Spinal contusion – hemorrhage in
the meninges which increases
pressure of the cerebral spinal
fluid
 Nervous tissue may be damaged
 Gradual recovery – may have some
residual damage
Spinal laceration – damage to the
spinal cord due to vertebral bone
fragments or foreign bodies
 Slower and less complete recovery
Spinal compression – the spinal cord
becomes squeezed and distorted
within the vertebral column
 Damage to the
cord will depend
upon the
severity of the
injury
Spinal transection – completely
severed spinal cord
 All motor and sensory function is absent
below the level of the injury
Treatment of Spinal Cord
Injuries
 Reduce pressure (possibly through
surgery)
 Stabilize (through halo traction or a
Stryker bed)
Halo traction
The Stryker Bed Frame
Functional Electrical
Stimulation
 FES is a means of producing
contractions in muscles, paralyzed due to
central nervous system lesions, by
means of electrical stimulation.
 The electrical stimulation is applied either
by skin surface electrodes or by
implanted electrodes
Current Research
Stem cell transplants – possibly
used for nerve growth and
repair
 9 days after the injury, embryonic stem
cells are packed around the site of the
injury
 Functional neurons have been shown to
develop in rats
Adult brain stem cells – the
adult brain contains inactive
stem cells
 Are there factors that would “turn on”
these cells for regeneration of nervous
tissue?
Antibodies – to promote healing
in the CNS
 With damage of the myelin sheath, an
inhibitory factor is released that slows
healing
 Researcher have found an antibiotic that
inactivates this inhibitory factor and will
speed up repairs
Buffalo Bill Kevin Everett
 http://www.nfl.com/videos/buffalobills/09000d5d8023c341/Doctors-updateEverett-s-condition
 http://www.myfoxhouston.com/dpp/health/1010
12-miracle-recovery-by-former-nfl-player
The Ear’s Role in
Balance and
Equilibrium
The Three Components of
Balance
Vestibular
Vision
Proprioception
Modified Clinical Test for
Sensory Interaction for
Balance
(CTSIB)
 http://www.youtube.com/watch?v=TMjRJvG4Os
The Ear
 Houses two senses
1. Hearing
2. Equilibrium (balance)
 Receptors are mechanoreceptors
 Different organs house receptors
for each sense
Anatomy of the Ear
 The ear is divided into three
areas
1. External ear
2. Middle ear
3. Inner ear
The External Ear


Involved in hearing only
Structures of the external ear
1. Pinna (auricle)
2. External auditory canal
The Middle Ear






Air-filled cavity within the temporal bone
Only involved in the sense of hearing
Two tubes are associated with the inner ear
 The opening from the auditory canal is covered by the tympanic
membrane
 The auditory tube connecting the middle ear with the throat
 Allows for equalizing pressure during yawning or swallowing
 This tube is otherwise collapsed
Three bones span the cavity
1. Malleus (hammer)
2. Incus (anvil)
3. Stapes (stirrup)
Vibrations from eardrum move the malleus
These bones transfer sound to the inner ear
The Inner Ear or Bony Labyrinth
 Includes sense organs
for hearing and balance
 Filled with perilymph
 A maze of bony
chambers within the
temporal bone
Organs of the Inner Ear
Semicircular canals – organ for dynamic
equilibrium
Cochlea – organ for
hearing
Vestibule – organ for
static equilibrium
Organs of Equilibrium

Receptor cells are in two structures
1. Vestibule (static)
2. Semicircular canals (dynamic)

Equilibrium has two functional parts
1. Static equilibrium
2. Dynamic equilibrium
Static Equilibrium
receptors are in the vestibule
Maculae – receptors on the
membranes of the
vestibule
 Report on the position of
the head
 Send information via the
vestibular nerve
Dynamic Equilibrium
receptors are in the semicircular
canals
Crista ampullaris – receptors in the
semicircular canals
 Tuft of hair cells
 Cupula (gelatinous cap) covers the
hair cells
Action of angular head movements
 The cupula stimulates the hair cells
 An impulse is sent via the vestibular
nerve to the cerebellum
Review of the balance and
equilibrium organs in the inner ear
I.
STATIC EQUILIBRIUM – position of the
head in space

The organ is the vestibule

The receptor inside the vestibule is
the maculae
II.
DYNAMIC EQUILIBRIUM – action of
angular head movements

The organ is the semicircular
canals

The receptor inside the semicircular
canals is the crista ampullaris
Symptoms of Meniere’s Disease
 The symptoms of Ménière’s disease are
episodic rotational vertigo (attacks of a
spinning sensation)
 Hearing loss
 Tinnitus (a roaring, buzzing, or ringing
sound in the ear)
 A sensation of fullness in the affected
ear.
Meniere’s Disease
 A disorder of the inner ear. Although the cause
is unknown, it probably results from an
abnormality in the fluids of the inner ear.
 Ménière’s disease is one of the most common
causes of dizziness originating in the inner ear.
 In most cases only one ear is involved, but
both ears may be affected in about 15 percent
of patients.
 Ménière’s disease typically starts between the
ages of 20 and 50 years. Men and women are
affected in equal numbers.
http://www.quietrelief.com/