Brain and Cranial Nerves

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  1. Meninges
    –Dura mater

    •Forms two layers:

    –external periosteal layer

    –internal meningeal layer

    • •Has
    • three extensions:

    –Falx cerebri

    –Falx cerebelli

    –Tentorium cerebelli

    –Arachnoid mater

    •Cobweb –like structure between dura mater and pia mater

    –Pia mater

    •Innermost, transparent layer

    •Attaches to the outer surface of the brain and spinal cord
  2. Spaces between and around meninges include the following
    –Sub-dural Space

    –Sub-arachnoid Space
  3. Blood Supply
    –Blood is supply to the brain by internal carotid and vertebral arteries

    –Blood is returned back to the heart by the jugular veins

    –Brain receives ~ 20% of blood supply

    •Requires constant supply of oxygen and glucose

    –The internal jugular veins are the venous return
  4. Blood brain barrier
    –Composed of tight junctions of endothelial cells of brain capillaries and associated astrocytes

    • –Restricts the passage of various chemical substances and pathogens from entering the
    • brain.
  5. Cerebrospinal Fluid
    • •Cerebrospinal Fluid (CSF) is a a clear fluid found in
    • the sub-arachnoid space, around the brain and spinal cord and within the cavities in the brain and spinal cord

    •Functions of the CSF:

    –Protects the brain and spinal cord

    •Absorbs shock

    –Transports nutrients and wastes

    •CSF Formation

    –Formed in the choroid plexuses by separation of fluid from blood

    •~140 ml of CSF at any given time in an adult human
  6. Ventricles
    •Ventricles are cavities within the brain and spinal cord filled with CSF.

    –Lateral ventricles

    –Third Ventricle

    –Cerebral Aqueduct

    –Fourth Ventricle
  7. Brain Stem
    •Brain Stem is composed of medulla, oblongata, pons and midbrain

    •Medulla oblongata

    –Lowest part of the brainstem

    –Composed of white mater and reticular formation network

    –Contain reflex center

    •Vital reflexes: cardiac, respiratory and vasomotor

    •Other reflexes: vomiting, sneezing, coughing and hiccupping

    –Site of decussation of pyramids (corticospinal tract

    Contain gustatory nucleus, cochlear nuclei, vestibular nuclei
  8. Nuclei of five pairs of cranial nerves
    •Vesibulocochlear (VIII) nerves

    •Glossopharyngeal (IX) nerves

    •Vagus (X) nerves

    •Accessory (XI) nerves

    •Hypoglossal (XII) nerves
  9. Pons
    –Located superiorly to medulla

    –Composed of sensory and motor tracts

    • –Houses nuclei associated with cranial nerves V (trigeminal nerve), VI (abducens nerve),
    • VII (facial nerve), and VIII (vestibulocochlear nerve)
  10. Midbrain
    • –Extends
    • from the pons to the diencephalon

    –Substantia Nigra

    –Red Nucleus


    •Superior colliculi

    •Inferior colliculi

    –Houses cranial nerves III (oculomotor nerve) and IV (trochlear nerve)
  11. On the anterior part of the midbrain are found the “little feet” of the cerebral peduncles.
    • –Contain axons of the corticospinal, corticobulbar, and corticopontine tracts which
    • conduct nerve impulses from motor areas in the cerebral cortex to the spinal cord, medulla, and pons, respectively.
  12. Reticular activating system (RAS)
    –Consists of sensory axons that project to

    the cerebral cortex.

    –Maintain consciousness

    –Inactivation produces sleep

    –Prevents sensory overload by filtering out insignificant information.
  13. Cerebellum (“little brain”) is located below the posterior portion of cerebrum
    –Separated from the cerebrum by transverse fissure and tentorium cerebelli

    –Gray matter compose the cortex

    –White matter predominates in the interior part of cerebellum
  14. Functions of the cerebellum
    • –Evaluates how well movements
    • initiated by motor areas are actually being carried out

    • –Together with cerebrum produces
    • skilled movement by coordinating the activities of groups of muscles

    –Control posture

    –Control skeletal muscles to maintain balance
Card Set:
Brain and Cranial Nerves
2012-04-15 20:11:24
lecture 15

human anatomy
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