1 / 47

Anatomy and Physiology of Balance

Anatomy and Physiology of Balance. Vestibular Hair Cells. Type I (aka inner) Type II (aka outer) With Kinocilium. The Semicircular Canals. posterior canal shares plane with contralateral anterior canal. horizontal canals share plane. Stimulated by Angular Acceleration.

dickinson
Download Presentation

Anatomy and Physiology of Balance

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Anatomy and Physiology of Balance

  2. Vestibular Hair Cells • Type I (aka inner) • Type II (aka outer) With Kinocilium

  3. The Semicircular Canals • posterior canal shares plane with contralateral anterior canal. • horizontal canals share plane.

  4. Stimulated by Angular Acceleration • greatest when fulcrum is within head • induces relative motion of endolymph • crista is displaced by fluid motion

  5. Responses of the Cristae • All kinocilia are oriented in the same direction • Crista in each pair of canals respond inversely to each other

  6. The Otolithic Organs Saccule: roughly vertical orientation, responds to acceleration components within saggital plane Utricle: horizontal (+ 30 deg.) orientation

  7. Excitation Patterns in the Utricle STRIOLA Anterior Posterior Medial

  8. Cranial Nerve VIII

  9. Vestibular Portion of C.N. VIII • superior division: utricle, anterior part of saccule, and horiz & anterior canals • inferior division: posterior part of saccule, and posterior canal • to vestibular nuclei • to cerebellum

  10. Vestibulocochlear Nerve • Exits temporal bone near its medial edge. • Enters lateral face of brainstem at the level of the lower pons. • Synapsing in (Cochlear and) Vestibular Nuclei

  11. Responses of Vestibular Neurons: • To changes in acceleration, but onset and fade slowly • For most normal head movements firing rates are in phase with head VELOCITY.

  12. Other inputs to vestibular nuclei: • Cerebellum: primarily inhibitory • Spinal cord • Pontine reticular formation • Contralateral vestibular nuclei

  13. From the Vestibular Nuclei: • Vestibulo-Oculomotor Pathways: • Direct: to oculomotor nuclei. • Indirect: via reticular formation to oculomotor nuclei (III IV and VI) • Vestibulo-Spinal Pathways: • Lateral V-S-throughout spinal cord • Medial V-S-cervical & thoracic • Reticulospinal tract-via brainstem reticular formation

  14. In the brainstem • Vestibular inputs undergo integration • Integrated signal is combined with original (velocity driven) signal • Processing to reset spatial map for eye musculature

  15. Ocular Musculature Superior Rectus (SR) Inferior Rectus (IR) Lateral Rectus (LR) Medial Rectus (MR) Superior Oblique (SO) Inferior Oblique (IO)

  16. Superior Rectus Superior Oblique Midline Lateral Rectus Medial Rectus Inferior Rectus Inferior Oblique

  17. The Oculomotor Cranial Nerves • III the oculomotor • IV the trochlear • VI the abducens

  18. III (Oculomotor) innervates: 1) Medial rectus 2) Superior rectus 3) Inferior rectus 4) Inferior oblique Levator palpebrae sup Pupillary sphincter Ciliary muscle

  19. IV (Trochlear) innervates: • Superior oblique

  20. VI (Abducens) innervates • Lateral rectus.

  21. Proprioceptive info from eye muscles • comes through Trigeminal nerve.

  22. Vestibulo-Ocular Reflex

  23. Horizontal/Lateral Canal VOR

  24. Anterior/Superior Canal VOR

  25. Posterior Canal VOR

  26. Central Nervous System Will Adapt to Peripheral Damage

  27. Eye Movements • Saccades—rapid shift in gaze • Pursuit—stabilize image of moving object • Fixation—stabilize image of still object • VOR—stabilize image during head motion • OKN—backup for when VOR decays to cont’d head rotation • Vergent movements—change depth of focus

  28. Saccades Pause cells inhibit Burst Neurons which stimulate: III & VI (horizontal) or III & IV (vertical)

  29. Compare, Select & Combine Senses Visual System Vestibular System Somato- Sensation SENSORY INPUTSVisionVestibularSomatosensory

  30. SOMATOSENSORY RECEPTORS Compare, Select & Combine Senses Somato- Sensation JointsPositionKinesthesia MusclesLengthTension SkinTouchPressure

  31. VISUAL RECEPTORS Compare, Select & Combine Senses Visual System CentralOrientation Navigation PeripheralMotion-sensitive Body-sway

  32. VESTIBULAR RECEPTORS Compare, Select & Combine Senses Vestibular System Semi-circular canalsOrientation Navigation Utricle & SacculeHorizontal & vertical acceleration & deceleration

  33. SENSORY ORGANIZATION Determination of BodyPosition Compare, Select & Combine Senses Visual Vestibular Somatosensory • Processingof inputs from the periphery Selection based on • Availability Accuracy • Valuefor the task at hand

  34. Functional Balance: Navigating in our Environment

More Related