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Brain

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Brain & Cranial Nerves Dr. Michael P. Gillespie Cranial Nerve VIII Vestibulocochlear Nerve Type: mixed (mainly sensory). Function: conveys impulses for ... – PowerPoint PPT presentation

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Title: Brain


1
Brain Cranial Nerves
  • Dr. Michael P. Gillespie

2
Major Parts of the Brain
  • Brain stem continuous with the spinal cord.
  • Medulla oblongata.
  • Pons.
  • Midbrain.
  • Cerebellum posterior to the brain stem.

3
Major Parts of the Brain
  • Diencephalon superior to the brain stem.
  • Thalamus.
  • Hypothalamus.
  • Cerebrum supported on the diencephalon and
    brain stem.
  • Largest part of the brain.

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Brain Blood Supply
  • Arteries
  • Internal carotid arteries
  • Vertebral arteries
  • Veins
  • Internal jugular veins

6
Brain Blood Flow
  • The brain consumes about 20 of the oxygen and
    glucose used at rest.
  • A brief slowing of blood flow may cause
    unconsciousness.

7
Brain Blood Flow
  • An interruption of blood flow for 1 to 2 minutes
    impairs neural function.
  • Total deprivation of oxygen for 4 minutes causes
    permanent injury.
  • If the blood entering the brain has a low level
    of glucose, mental confusion, dizziness,
    convulsions, and loss of consciousness may occur.

8
Blood Brain Barrier
  • The blood-brain barrier (BBB) protects the brain
    from harmful substances and pathogens.
  • It prevents the passage of many substances from
    the blood to the brain tissue.
  • Tight junctions seal together endothelial cells
    of brain capillaries.
  • Astrocytes selectively allow some substances
    through and not others.

9
Breaching the BBB
  • The BBB prevents the passage of harmful
    substances into the brain, but it also prevents
    the passage of useful drugs.
  • Drugs are injected in a concentrated sugar
    solution to facilitate passage.
  • The high osmotic pressure causes cells lining the
    barrier to shrink and makes the membrane leaky.

10
Protective Coverings
  • Cranial Meninges.
  • Dura mater.
  • Arachnoid mater.
  • Pia mater.

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Cerebrospinal Fluid (CSF)
  • Clear colorless liquid.
  • Protects the brain and spinal cord from chemical
    and physical injuries.
  • Carries oxygen, glucose, and other needed
    chemicals from the blood to the neurons and
    neuroglia.
  • Circulates in the subarachnoid space (between the
    arachnoid mater and pia mater).

13
Protective Coverings
  • Extensions of the dura mater separate the parts
    of the brain.
  • Falx cerebri separates the two hemispheres of
    the cerebrum.
  • Falx cerebelli separates the two hemispheres of
    the cerebellum.
  • Tentorium cerebelli separates the cerebrum from
    the cerebellum.

14
Formation of CSF in the Ventricles
  • CSF is formed in the ventricles.
  • Formed by ependymal cells that cover the choroid
    plexuses of the ventricles.

15
Formation of CSF in the Ventricles
  • There are 4 ventricles.
  • Functions of CSF.
  • Mechanical protection.
  • Shock absorption.
  • Buoys the brain.
  • Chemical protection optimal chemical
    environment.
  • Circulation medium of exchange for wastes and
    nutrients.

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Hydrocephalus
  • Abnormalities of the brain can interfere with
    drainage of CSF from the ventricles and
    subarachnoid space.
  • CSF pressure increases causing hydrocephalus.
  • In infants this causes the fontanels to budge.

21
Hydrocephalus
  • Tumors, inflammation, developmental malformations
    can all cause hydrocephalus.
  • Pressure buildup can damage the delicate nervous
    tissue.
  • A surgeon can implant a drain line called a shunt
    to divert CSF.
  • In adults, hydrocephalus may occur after head
    injury, meningitis, or subarachnoid hemorrhage.

22
Brain Stem
  • Between the brain and spinal cord.
  • 3 regions.
  • Medulla oblongata.
  • Pons.
  • Midbrain.

23
Medulla Oblongata
  • A continuation of the spinal cord.
  • Sensory (ascending) tracts and motor (descending)
    tracts travel through the white matter of the
    medulla.
  • Many nerves decussate (cross over) in the medulla.

24
Medulla Oblongata
  • Cardiovascular center regulates the heartbeat and
    the diameter of the blood vessels.

25
Medulla Oblongata
  • The medullary rhythmicity area adjusts the rhythm
    of the breathing and controls reflexes for
    vomiting, coughing, and sneezing.

26
Medulla Oblongata
  • The nuclei for the following cranial nerves
    reside in the medulla
  • VIII (vestibulocochlear).
  • IX (glossopharyngeal).
  • X (vagus).
  • XI (accessory).
  • XII (hypoglossal).

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Pons
  • Pneumotaxic area and apneustic area regulate
    breathing.
  • Nuclei for cranial nerves V (trigeminal), VI
    (abducens), VII (facial), and VIII
    (vestibulocochlear).

30
Midbrain
  • The midbrain or mesencephalon contains the
    superior colliculi (visual actvities) and
    inferior colliculi (auditory pathways).
  • The midbrain contains the substantia nigra which
    release dopamine to help control subconscious
    muscle activities. Loss of these neurons results
    in Parkinson disease.
  • Cranial nerves III (oculomotor) and IV
    (trochlear) originate here.

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Cerebellum
  • The second largest part of the brain.
  • A main function of the cerebellum is to evaluate
    how well movements are being carried out and
    correct for discrepancies. This helps to smooth
    out movements.

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Diencephelon
  • Epithalamus.
  • Contains the pineal gland which secretes
    melatonin.
  • Thalamus.
  • Relays sensory information to the cortex.
  • Provides crude perception of touch, pressure,
    pain, and temperature.

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Diencephelon
  • Subthalamus.
  • Controls body movements.
  • Hypothalamus.
  • Controls and integrates activities of the ANS.
  • Regulates emotional and behavioral patterns.
  • Regulates cicadian rhythms.
  • Regulates eating and drinking behavior.
  • Produces hormones oxytocin and ADH.

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Cerebrum
  • Sensory areas interpret sensory impulses.
  • Motor areas control muscular movement.
  • Association areas function in emotional and
    intellectual processes.
  • Basal areas regulate gross muscle movements and
    regulate muscle tone.
  • Limbic system functions in survival behaviors.

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Brain Injuries
  • Concussion an abrupt, temporary loss of
    consciousness following a blow to the head.
  • Most common brain injury.
  • Signs headache, drowsiness, lack of
    concentration, confusion, amnesia.

43
Brain Injuries
  • Contusion bruising of the brain due to trauma
    and includes leakage of blood.
  • Signs - immediate loss of consciousness,
    transient cessation of respiration, decreased
    blood pressure.

44
Brain Injuries
  • Laceration tear of the brain usually from a
    skull fracture or gunshot wound.
  • Rupture of large blood vessels.
  • Consequences cerebral hematoma (localized pool
    of blood, usually clotted), edema, and increased
    intracranial pressure.

45
Cerebral Cortex Areas and Functions
  • Sensory areas receive and interpret sensory
    information.

46
Cerebral Cortex Areas and Functions
  • Motor areas initiate movements.
  • Association areas deal with integrative
    functions
  • Memory.
  • Emotions.
  • Reasoning.
  • Will.
  • Judgement.
  • Personality.
  • Intelligence.

47
Sensory Areas
  • Primary somatosensory area receives sensations
    for touch, proprioception, pain, itching, tickle,
    and thermal sensations.
  • Located in the postcentral gyrus of the parietal
    lobes.
  • Primary visual area.
  • Primary auditory area.
  • Primary gustatory area taste.
  • Primary olfactory area.

48
Motor Areas
  • Primary motor area located in the precentral
    gyrus of the frontal lobe.
  • Brocas speech area coordinates the
    contractions of speech and breathing muscles.

49
Association Areas
  • Somatosensory association area integrates and
    interprets sensations.
  • Visual association area evaluates what is seen.
  • Auditory association area evaluates sounds.

50
Association Areas
  • Wernickes (posterior language) area interprets
    the meaning of speech.
  • Common integrative area.
  • Premotor area controls learned skilled
    movements.
  • Frontal eye field area controls voluntary
    scanning movements of the eyes.

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Aphasia
  • An inability to use or comprehend words.

53
Aphasia
  • Damage to Brocas area results in nonfluent
    aphasia.
  • Inability to properly articulate to form words.
  • These people know what they wish to say, but
    cannot speak.

54
Aphasia
  • Damage to the auditory association area results
    in fluent aphasia.
  • Faulty understanding of spoken words.
  • Word deafness inability to understand spoken
    words.
  • Word blindness inability to understand written
    words.

55
Cranial Nerve I - Olfactory
  • Type sensory.
  • Function smell.
  • Anosmia loss of sense of smell.

56
Cranial Nerve II Optic Nerve
  • Type sensory.
  • Function vision.
  • Anopia blindness in one or both eyes.

57
Cranial Nerve III - Oculomotor
  • Type mixed (mainly motor).
  • Function movement of the upper eyelid and
    eyeball. Accomodation of the lens for nearn
    vision and constriction of the pupil.
  • Strabismus deviation of the eye in which both
    eyes dont focus on the same object.
  • Ptosis drooping of the upper eyelid.
  • Diploia double vision.

58
Cranial Nerve IV Trochlear Nerve
  • Type mixed (mainly motor).
  • Function movement of the eyeball.
  • Diplopia and strabismus occur with trochlear
    nerve damage.

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Cranial Nerve V Trigeminal Nerve
  • Type mixed.
  • Function conveys impulses for touch, pain,
    temperature and proprioception. Chewing.
  • Trigeminal neuralgia (tic douloureux) pain to
    branches of the trigeminal nerve.
  • Dentists apply anesthetic to branches of this
    nerve.

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Cranial Nerve VI - Abducens
  • Type mixed (mainly motor).
  • Function movement of the eyeball.
  • With damage to this nerve the eye cannot move
    laterally beyond the midpoint and usually points
    medially.

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Cranial Nerve VII Facial Nerve
  • Type mixed.
  • Function Propriception and taste. Facial
    expression. Secretion of saliva and tears.
  • Injury produces bells palsy (paralysis of facial
    muscles).

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Cranial Nerve VIII Vestibulocochlear Nerve
  • Type mixed (mainly sensory).
  • Function conveys impulses for equilibrium and
    hearing.
  • Injury can cause vertigo, ataxia (muscular
    incoordination), nystagmus (rapid movement of the
    eyeball), and tinnitus.

67
Cranial Nerve IX Glossopharyngeal Nerve
  • Type mixed.
  • Function taste and somatic sensations from the
    posterior 1/3 of the tongue. Elevates the
    pharynx during swallowing and speech. Stimulates
    the secretion of saliva.
  • Injury causes decreased salivary secretion, loss
    of taste, and difficulty swallowing.

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Cranial Nerve X Vagus Nerve
  • Type mixed.
  • Function taste and somatic sensations.
    Swallowing, coughing, and voice production.
    Regulates GI tract and heart rate.
  • Injury interferes with swallowing, paralyzes
    vocal cords, and causes the heart rate to
    increase.

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Cranial Nerve XI Accessory Nerve
  • Type mixed (mainly motor).
  • Function Proprioception. Swallowing, movement
    of head and shoulders.
  • If the nerves are damaged the SCM and Trapezius
    become paralyzed.

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Cranial Nerve XII Hypoglossal Nerve
  • Type mixed (mainly motor).
  • Function Proprioception. Movement of the tongue
    during speech and swallowing.
  • Injury results in difficulty in chewing,
    speaking, and swallowing. When protruded, the
    tongue curls towards the affected side and
    atrophies on the affected side.

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Cranial Nerves
  • On Old Olympus Towering Tops A Fin And German
    Viewed Some Hops.
  • This mnemonic device helps you memorize the names
    of the cranial nerves.
  • The first letter from each word corresponds to
    the first letter of each cranial nerve.
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