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Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
Vestibular sysstem
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Vestibular sysstem

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these is 20 minutes presentation on vestibular system,presented by girmay fitiwi addis ababa university ,medical faculity departement of medical physiology.

these is 20 minutes presentation on vestibular system,presented by girmay fitiwi addis ababa university ,medical faculity departement of medical physiology.

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  • 1. Addis Ababa UniversityCollege of Health ScienceDepartment of Medical Physiology
    Presentation on physiology of vestibular apparatus and clinical correlates
    By Girmay F.
    1
    8/10/2011
  • 2. Presentation Out line
    Objectives
    Introduction
    Anatomy of Vestibular apparatus
    3.1 The otolithic organs
    3.2 Semicircular canals
    3.3 Structures of hair cell and genesis action potential
    4.Function of the utricle and saccule
    5. Function of semicircular ducts.
    6. Neural connection of vestibular nuclei
    7. vestibule-ocular reflex.
    8. Vestibular dysfunction
    9. References
    8/10/2011
    2
  • 3. 1.Objectives
    At the end of presentation ,students expected to
    1.Describe the anatomy and function of the vestibular apparatus
    2.Explain the major input and out put of vestibular nuclei
    3.Discuss the importance of vestibule ocular reflex.
    4.List some clinical disorders of body equilibrium.
    8/10/2011
    3
  • 4. 2.Introduction
    Gravity or acceleration tends to cause displacement of the body from equilibrium.
    Posture is back ground position which helps in carrying out a specific movement to desired target.
    Postural reflexes are integrated at various levels of the neural axis.
    The vestibular system has important sensory functions, contributing to the perception of self-motion, head position, and spatial orientation relative to gravity.
    It help to stabilize gaze head, and posture.
    8/10/2011
    4
  • 5. 3.Anatomy of Vestibular apparatus
    located in the petrous portion of the temporal bone, called Bony labyrinth.
    Membranous labyrinth
    The membranous labyrinth is the functional unit of vestibular apparatus.
    Compose of
    • cochlea
    • 6. semicircular canals
    • 7. two otolith organs.
    8/10/2011
    5
    Fig.1.membranous labyrinth
  • 8. 3.1 Otolith organs
    Membrane bound sac like structure ,Utricle and saccule.
    • Detect linear acceleration
    • 9. Detect orientation of head with respect to gravity.
    • 10. Macula is the sensory organ
    • 11. Located on the inside surface of each utricle and saccule
    • 12. Macula 2 mm in diameter.
    fig.2. location of macula
  • 13. otolithic organs Cont’d
    Containing
    - sustentacular cells
    - numerous hair cells
    the Cilia embedded in gelatinous layer called statoconia.
    Impregnated with calcium carbonate crystals which are called otoconia or ear dust
    Base and side of hair cells vestibular nerve.
    8/10/2011
    7
    Fig.5.structure of macula
  • 14. Otolithic organs Cont’d
    The macula of utricle
    Mainly in horizontal plane.
    Hair cells oriented vertically up ward
    Determining orientation of the head when the head is in up right position.
    Respond to:-
    1.changes in head position
    • fore and aft lift
    2.Linear acceleration in horizontal plane
    • running
    8/10/2011
    8
    Saccule
    Utricle
    Fig.3 anatomical orientation of macula
  • 15. Otolithic organs cont’d
    • oriented in vertical plane
    • 16. Hair cells arising in horizontal plane
    Respond to:-
    • changes in head position
    supine position
    • Linear acceleration in vertical plane.
    jumping down
    8/10/2011
    9
    Saccule
    Utricle
    Fig.4.anatomical orientations of maculae
  • 17. 3.2 Semicircular canals
    Detect angular acceleration
    There are 3 canals
    • Superior
    • 18. Horizontal(lateral)
    • 19. posterior
    • 20. Right angles to each other
    Each canal is a continuous endolymph-filled .     
    Enlargement at one of its end called ampulla.  
    8/10/2011
    10
    Fig.6.parts of SCC.
  • 21. Semicircular canals Cont’d
    Ampulla containing a receptor organ called crista ampullaris.
    The projecting cilia are embedded in gelatinous mass called cupula.
    The cupula extends right across the lumen up to the opposite wall of ampulla.
    8/10/2011
    11
    Fig.7.structure of crista ampullaris
  • 22. 3.3 Structure of hair cells and genesis of action potential
    Each hair cell has about 50-70 stereocilia and one kinocilium.
    Arising from its apical end.
    Stereocilia and the kinocilium are connected by tip links
    8/10/2011
    Fig.8 structure of hair cell
    12
  • 23. Structure of hair cells Cont’d
    8/10/2011
    13
    Fig.9.A,B,C
  • 24. structure of hair cells Cont’d
    When stereocilia bend towards kinocilium membrane receptor depolarization the impulse traffic increases
    When stereocilia bend away from kinocilium membrane receptor repolarization decreases the impulse traffic
    Orientation of the head in space changes and the weight of the statoconia bend the cilia, appropriate signals are transmitted to the brain to control equilibrium.
    8/10/2011
    14
  • 25. 4.The function of utricle and saccule
    1.Detection of Linear acceleration
    When the body suddenly thrust forward-(i.e. the body accelerates)
    The statoconia,fallbackward on the hair cell cilia, and information of dysequilibrium is sent into the nervous centers, causing the person to feel as though he or she were falling backward.
    This automatically causes the person to lean forward until the resulting anterior shift of the statoconia exactly equals the tendency for the statoconia to fall backward because of the acceleration.
    8/10/2011
    15
  • 26. 5.The function of Utricle and Saccule cont’d
    2.Maintenance of static equilibrium
    The hair cells are all oriented in different directions in the maculae of the utricles and saccules, so that with different positions of the head, different hair cells become stimulated.
    The “patterns” of stimulation of the different hair cells apprise the brain of the position of the head with respect to the pull of gravity.
    In turn, the vestibular, cerebellar, and reticular motor nerve systems of the brain excite appropriate postural muscles to maintain proper equilibrium.
    8/10/2011
    16
  • 27. The function 0f Semicircular Ducts
    Detect angular acceleration
    Rotational acceleration stimulates crista ampullaris.
    The endolymph is displaced in a direction opposite to the direction of rotation.
    The fluid pushes on the cupula, deforming it.
    8/10/2011
    Fig.10.movement of SCC with body
    17
  • 28. The function of semicircular ducts cont’d
    this bends the processes of the hair cells.
    When a constant speed of rotation is reached
    the fluid rotate at the same rate as the body and the cupula swings back into the upright position .
    8/10/2011
    18
  • 29. The function of semicircular canals Cont’d
    When rotation is stopped, deceleration produces
    • displacement of the endolymph in the direction of the rotation, and the cupula is deformed in a direction opposite to that during acceleration.
    • 30. It returns to mid position in 25 to 30 seconds.
    8/10/2011
    Fig.11.mov’t of endolymph with respect to SCCs
    19
  • 31. The function of semicircular canals Cont’d
    Simultaneously, the cilia at the top of the hair cell are bent. If the direction of bending is towards the kinocilium, depolarization takes place.
    Bending of the cilia in the reverse direction causes hyperpolarization; this alters impulse traffic along the nerves innervating the hair cells.
    8/10/2011
    20
  • 32. 6.Neuronal connection of the vestibular nuclei
    Vestibular nuclei
    Four major vestibular nuclei, some minor subgroups.
    Input
    • vestibular receptors
    • 33. Cerebellum, Brain stem
    • 34. Spinal cord
    • 35. cerebra cortical areas.
    8/10/2011
    Fig.12.inputs of vestibular nuclei
    21
  • 36. Neuronal connection of vestibular nuclei cont’d
    • Ganglion of Scarpa, which is situated in the upper part of the outer end of the internal auditory meatus.
    8/10/2011
    22
    Fig.13.pathways for equilibrium sensation
  • 37. Neural connection of vestibular nuclei cont’d
    Primary cortical center for equilibrium located in the parietal lobe.
    Flocculonodular lobe of cerebellum concerned with dynamic equilibrium.
    8/10/2011
    23
    Fig.14 Inputs and out puts of vestibular nuclei
  • 38. Neural connection of vestibular nuclei cont’d
    8/10/2011
    Fig.14.
    24
  • 39. Neural connection of vestibular nuclei cont’d
    8/10/2011
    Fig.15.descending projection of vestibular nuclei to spinal cord
    25
  • 40. Neural connection of vestibular nuclei cont’d
    Descending projections from the medial and lateral vestibular nuclei to the spinal cord.
    The MVN project bilaterally in the MLF to reach the medial part of the ventral horns and mediate head reflexes in response to activation of semicircular canals.
    The LVN sends axons via the LVT to contact anterior horn cells innervating the axial and proximal limb muscles.
    Neurons in the LVN receive input from the cerebellum, allowing the cerebellum to influence posture and equilibrium.
    8/10/2011
    26
  • 41. 7.Vestibulo ocular reflex
    Stabilizes images on retina during head movement .
    When rotation starts, the eyes move slowly in a direction opposite to the direction of rotation, maintaining visual fixation.
    When the limit of this movement is reached, the eyes quickly snap back to a new fixation point and then again move slowly in the other direction.
    8/10/2011
    27
    Fig.16. VOR
  • 42. Cont’d
    • For example, horizontal movement of the two eyes toward the right requires contraction of the left medial and right lateral rectus muscles.
    8/10/2011
    Fig.17.neural projection associated with VOR
    28
  • 43. 8.Vestibular dysfunction
    Peripheral vestibular disorder
    Central vestibular disorder
    Loss of equilibrium and postural adjustments.
    PVD = neuritis, labyrinthitis,meniere’s disease, BPPV,and following surgery .
    8/10/2011
    29
  • 44. 8.1Benign paroxysmal positional vertigo
    the most common vestibular disorder
    characterized by episodes of vertigo that occur with particular changes in body position.
    Possible cause is that otoconia from the utricle separate from the otolith membrane and become lodged in the cupula of the posterior semicircular canal.
    This causes abnormal deflections when the head changes position relative to gravity.
    8/10/2011
    30
  • 45. 8.2 Central vestibular disorder
    Primarily involve the vestibular nucleicomplex and the cerebellum, as well as structures of the reticular activating system,midbrain, and higher centers of cortical function.
    Affect integration and processing of sensory input from the vestibular,visual, and somatosensory systems.
    Most common cause of CVD includes
    • brainstemstrokes, head trauma, migraine-related vestibulopathy
    • 46. multiple sclerosis, and cerebellar degeneration.
    8/10/2011
    31
  • 47. 8.3 Nystagmus
    jerky movement of the eye observed at the start and end of a period of rotation.
    Back and forth or rotational eye movements. The movements will be slower in one direction.
    The direction of eye movement is identified by the direction of the quick component.
    8/10/2011
    32
  • 48. 8.4 Motion sickness
    Excessive vestibular stimulation
    The symptoms are probably due to reflexes mediated via vestibular connections in the brain stem and the flocculonodular lobe of the cerebellum.
    symptom
    Nausea, blood pressure changes, sweating, pallor
    8/10/2011
    33
  • 49. 9.References
    Berne and levy physiology 6thedition,bruce m koeppen and Bruce A. Stanton.
    Guyton and hall text book of medical physiology,12th edition, Philadelphia: Elsevier Inc.
    Ganong’s review of medical physiology 23th edition. Mc Graw Hill
    Neuroscience exploring the brain Third Edition.Dale Purves George J. Augustine, Sinauer Associates, Inc. Publishers Sunderland, Massachusetts U.S.A.
    Internet websites
    8/10/2011
    34
  • 50. Thank you !!!
    8/10/2011
    35

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