THE NERVOUS SYSTEM

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THE NERVOUS SYSTEM
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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

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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

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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

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Motor (efferent) division

• Two subdivisions
• Somatic nervous system voluntary
• 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)

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Structural Classification of the Nervous System
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Organization of the Nervous System
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Nervous Tissue Neurons

• Neurons nerve cells
• Cells specialized to transmit messages

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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

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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

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Major Regions of Neurons

• Schwann cells produce myelin sheaths in
  jelly-roll like fashion
• Nodes of Ranvier gaps in myelin sheath along
  the axon

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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

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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)

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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

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Human Reflex Physiology

• http//www.youtube.com/watch?vHfuhVWK8C0U

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Human Reflex Physiology

• Do the lab activity here

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Functions in Motor Neurons

• Efferent neurons go to the muscle fibers (motor
  neurons)
• Neuron muscle fiber ratio
• 110 fibers in delicate, precise movements (eye
  muscles)
• 1340 fibers in finger muscles
• 11800 fibers in gastroc muscles
• 12,000-3,000 fibers in largest muscles

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• Neurons can facilitate - set off an excitatory
  response
• neurons can inhibit a muscle does not fully
  contract all fibers at the same time.

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• 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

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• Twitch characteristics
• how muscle fibers respond
• motor units respond with high or low tension

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FAST TWITCH MUSCLE FIBERS

• ?large motor neurons
• ?fast conduction velocity
• ?high force
• ?quickly reaches peck tension
• ?fatigues quickly
• ?many developed in weight lifters

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SLOW TWITCH MUSCLE FIBERS

• ?small motor neurons
• ?slow conduction velocity
• ?low force
• ?slow to reach tension
• ?fatigue resistant
• ?many developed in runners

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• 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

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• 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

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FAST TWITCH MUSCLE FIBERS

• http//www.youtube.com/watch?vR7dCi1rOMq4

http//www.youtube.com/watch?vco9NjWkrLII
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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)

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RECEPTORS IN MUSCLES AND TENDONS(PROPRIOCEPTION)
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• 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.

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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

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• Hold a book with your eyes closed you are able
  to maintain the elbow at 90?

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spindles to sensory neurons (afferent) to SC
to motor (efferent) neurons - to the muscle
fibers (modify movement or posture)
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Muscle Spindles

• http//www.youtube.com/watch?vF871bBWS4oY

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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

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Golgi Tendon Organs

• http//www.youtube.com/watch?v7T4NI_2qDEM

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Regions of the Brain
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Regions of the Brain

• Cerebral hemispheres (cerebrum)
• Diencephalon
• Brain stem
• Cerebellum

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Cerebral Cortex(cerebrum)

• Contains sensory and motor centers
• Contains areas for memory, learning and thought

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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

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Are you right brained or left brained?
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• The Right Brain vs Left Brain test ... do you see
  the dancer turning clockwise or
  counter-clockwise?
• http//www.news.com.au/heraldsun/story/0,21985,225
  56281-661,00.html

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RIGHT BRAIN FUNCTIONS (clockwise direction) LEFT BRAIN FUNCTIONS (counter-clockwise direction)
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Surface lobes of the cerebrum

• Frontal lobe
• Parietal lobe
• Occipital lobe
• Temporal lobe

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Specialized Areas of the Cerebrum

• Somatic sensory area receives impulses from the
  bodys sensory receptors
• Primary motor area sends impulses to skeletal
  muscles
• Brocas area involved in our ability to speak

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Cerebral areas involved in special senses

• Gustatory area (taste)
• Visual area
• Auditory area
• Olfactory area

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Interpretation areas of the cerebrum

• Speech/language region

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Diencephalon

• Sits on top of the brain stem
• Regulates autonomic nervous functions
• Body temperature
• Blood pressure
• Sleep
• Emotions
• Made up of
• Thalamus
• Hypothalamus
• Epithalamiums

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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

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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

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• Take a look at the sheep brain

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• CEREBRAL CORTEX
• (conscious experience, perception, and planning)
• input
• ?
• CEREBELLUM
• ?
• input
• BRAIN STEM AND SPINAL CORD (body positioning and
  proprioception)

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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

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• Some scientists believe that mental activities
  may be coordinated in the cerebellum the same way
  motor activities are coordinated.

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• The cerebellum uses constant proprioceptive
  information (feedback on body positioning) to
  fine-tune motor movements.

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• The cerebellum contains more neurons than any
  other part of the brain and can process
  information faster than any other part of the
  brain.

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• Cerebellar dysfunction results in problems
  walking, balance, and accurate hand and arm
  movement

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• Cerebellar function is important for language
  processing and selective attention. It may be
  associated with dyslexia and autism.

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• 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.

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Cerebellar Dysfunction

• http//www.youtube.com/watch?vjx9Eq6Jxg9s
• http//www.youtube.com/watch?veBvzFkcvScgfeature
  player_embedded
• http//www.youtube.com/watch?vjnQcKAYNuyk
• http//www.youtube.com/watch?vxLlL24shW7E

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Traumatic Brain Injuries
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• Concussion
• Slight brain injury
• No permanent brain damage

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• Contusion
• Nervous tissue destruction occurs
• Nervous tissue does not regenerate

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• 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).
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• Cerebral hemorrhage
• The rupture of a blood vessel supplying blood to
  a region of the brain

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Neurological Disorders
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• 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

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• Alzheimers 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

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An Alzheimer Brain
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• Parkinsons Disease
• the chemical, dopamine, allows smooth,
  coordinated function of the body's muscles and
  movement
• dopamine-producing cells are damaged
• usually strikes people in their 50s
• symptoms include
• tremor (shaking)
• slowness of movement
• rigidity (stiffness)
• difficulty with balance

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• Huntingtons 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

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• Multiple Sclerosis
• is usually diagnosed in a person in their 20s
• thought to be an autoimmune disease of the CNS
• myelin sheaths are destroyed and replaced by scar
  tissue
• this disrupts the neurons ability to conduct
  impulses
• symptoms include

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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

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• Neurological Diagnostics

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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

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Electroencephalogram
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Cerebral Angiogram

• Dye into the blood stream and then x-rayed
• Allows assessment of the blood supply to the
  brain (carotid arteries) and cerebral arteries
• Allows you to see narrowing of the arteries

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Cerebral Angiogram
Cerebral angiogram shows the aneurysm (arrows)
that was responsible for the bleed.
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CAT scan Computerized Axial Tomography

• A powerful x-ray
• Shows soft tissue as well as bone

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CAT scan Computerized Axial Tomography
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MRI Magnetic Resonance Imaging

• Magnetism causes alignment of water molecules
• This allows imaging of body tissues by density

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MRI Magnetic Resonance Imaging
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PET scan

• High energy gamma rays
• Monitors biochemical activity can detect any
  metabolic abnormalities

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PET scan
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Spinal Cord Injuries
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Spinal Shock any sever injury to the spinal
cord that produces a short period of sensory and
motor paralysis

• 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

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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

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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

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Spinal laceration damage to the spinal cord due
to vertebral bone fragments or foreign bodies

• Slower and less complete recovery

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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

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Spinal transection completely severed spinal
cord

• All motor and sensory function is absent below
  the level of the injury

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Treatment of Spinal Cord Injuries

• Reduce pressure (possibly through surgery)
• Stabilize (through halo traction or a Stryker bed)

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Halo traction
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The Stryker Bed Frame
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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

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Current Research
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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

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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?

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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

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Buffalo Bill Kevin Everett

• http//www.nfl.com/videos/buffalo-bills/09000d5d80
  23c341/Doctors-update-Everett-s-condition
• http//www.myfoxhouston.com/dpp/health/101012-mira
  cle-recovery-by-former-nfl-player

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• The Ears Role in Balance and Equilibrium

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The Three Components of Balance

• Vestibular
• Vision
• Proprioception

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Modified Clinical Test for Sensory Interaction
for Balance(CTSIB)

• http//www.youtube.com/watch?vTMjR-JvG4Os

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The Ear

• Houses two senses
• Hearing
• Equilibrium (balance)
• Receptors are mechanoreceptors
• Different organs house receptors for each sense

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Anatomy of the Ear

• The ear is divided into three areas
• External ear
• Middle ear
• Inner ear

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The External Ear

• Involved in hearing only
• Structures of the external ear
• Pinna (auricle)
• External auditory canal

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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
• Malleus (hammer)
• Incus (anvil)
• Stapes (stirrup)
• Vibrations from eardrum move the malleus
• These bones transfer sound to the inner ear

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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

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Organs of the Inner Ear
Semicircular canals organ for dynamic
equilibrium
Cochlea organ for hearing
Vestibule organ for static equilibrium
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Organs of Equilibrium

• Receptor cells are in two structures
• Vestibule (static)
• Semicircular canals (dynamic)
• Equilibrium has two functional parts
• Static equilibrium
• Dynamic equilibrium

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Static Equilibriumreceptors 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

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Dynamic Equilibriumreceptors 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

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Review of the balance and equilibrium organs in
the inner ear

• STATIC EQUILIBRIUM position of the head in
  space
• The organ is the vestibule
• The receptor inside the vestibule is the maculae
• DYNAMIC EQUILIBRIUM action of angular head
  movements
• The organ is the semicircular canals
• The receptor inside the semicircular canals is
  the crista ampullaris

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Symptoms of Menieres Disease

• The symptoms of Ménières 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.

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Menieres 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.
• Ménières 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.
• Ménières disease typically starts between the
  ages of 20 and 50 years. Men and women are
  affected in equal numbers.

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