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Motor physiology

Motor physiology. S.A.A MORTAZAVI MD Associate professor of ophthalmology Isfahan university of medical sciences 2011 - 1390. Axes of FICK. X-axis a transverse axis passing through the center of the eye at the equator Y-axis a sagital axis passing through the pupil

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Motor physiology

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  1. Motor physiology S.A.A MORTAZAVI MD Associate professor of ophthalmology Isfahan university of medical sciences 2011 - 1390

  2. Axes of FICK • X-axis a transverse axis passing through the center of the eye at the equator • Y-axis a sagital axis passing through the pupil • Z-axis a vertical axis

  3. Voluntary vertical rotations of the eye occur about X axis • Voluntary horizontal rotations of the eye occur about Z axis • Involuntary torsional rotations of the eye occur about Y axis

  4. listing’s equatorial plane • The center of rotation and includes the X and Z axes • The Y axis is perpendicular to this plane

  5. Positions of Gaze • Primary position : straight ahead • Secondary positions : straight up ,straight down, right ,left • Tertiary positions : up & right, up & left, down & right, down & left

  6. Arc of contact • The point of effective or physiologic insertion is the tangential point where the muscle first contacts the globe • The action of the eye muscle : a vector of force that acts at this tangential point to rotate the eye • The length of muscle actually in contact with the globe

  7. Monocular eye movements • Adduction:movement of the eye nasally • Abduction:movement of the eye temporally • Elevation (supraduction): upward rotation • Depression (infraduction): downward rotation • Intorsion (incycloduction):nasal rotation of the superior portion of the vertical corneal meridian • Extorsion(excycloduction):temporal rotation of the superior portion of the vertical corneal meridian

  8. Agonist: the primary muscle moving the eye in a given direction • Synergist: the muscle in the same eye as the agonist that acts with the agonist to produce a given movement • Antagonist: the muscle in the same eye as the agonist that acts in the direction opposite to that of the agonist

  9. Sherrington’s law • Increased innervational and contraction of a given muscle are accompanied by a reciprocal decrease in innervation and contraction of its antagonist

  10. Binocular eye movements • Version: eye movements conjugate and the eyes move in the same direction • Vergence: eye movements disconjugate and the eyes move in opposite directions

  11. versions • Dextroversion : movement of both eyes to the patient’s right • Levoversion : movement of both eyes to the patient’s left • Elevation : upward rotation of both eyes • Depression : downward ratation of both eyes • Dextrocycloversion : both eyes rotate so that the superior portion of the vertical corneal meridian moves to the patient’s right • Levocycloversion : movement of both eyes so that the superior portion of the vertical corneal meridian rotates to the patient’s left

  12. Yoke muscles • Two muscles (one in each eye ) that are the prime movers of their respective eyes in a given position of gaze

  13. Cardinal positions • The six positions of gaze in which one muscle of each eye is the prime mover are known as the cardinal positions of gaze

  14. Hering’s law • Equal and simultaneous innervation flows to yoke muscles concerned with the desired direction of gaze • Important clinical implications especially when dealing with a paralytic or restrictive strabismus

  15. Primary deviation: the amount of misalignment when the normal eye is fixating • Secondary deviation: the amount of misalignment when the paretic or restrictive eye is fixating • The secondary deviation is larger than the primary deviation

  16. vergence • Convergence: movement of both eyes nasally relative to a given position • Divergence: movement of both eyes temporally relative to a given position • Vertical vergence: less frequently encountered ,can also occur; one eye moves upward and the other downward

  17. Incyclovergence : a rotation of both eyes so that the superior portion of each vertical corneal meridian rotates the toward the median plane • Excyclovergence : a rotation of both eyes so that the superior portion of each vertical meridian rotates away from the median plane

  18. Tonic convergence :the constant innervational tone to the extraocular muscles when a person is awake and alert • Accommodative convergence of the visual axes : part of the synkinetic near reflex • Voluntary convergence : a conscious application of the near synkinesis

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