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The Vestibular System - Coggle Diagram

- - - - vestibular nuclei also receive inputs from other parts of the brain and the visual and somatic sensory systems
        
        project to a variety of targets above them in the brain stem, and below them into the spinal cord
        
        e.g. otolith organ axons → lateral vestibular nucleus → vestibulospinal tract → leg muscles
        
        also send axons into the ventral posterior (VP) nucleus of the thalamus
        
        projects to regions close to the representation of the face in the primary somatosensory and primary motor areas of cortex
  - - - accurate vision requires an image to remain stable on the retinas despite movement of the head
      - set of six extraocular muscles
        
        VOR works by sensing rotations of the head and immediately commanding a compensatory movement of the eyes in the opposite direction.
        
        e.g. head turns left, VOR induces eyes to turn right
        
        Axons from the left horizontal semicircular canal innervate the left vestibular nucleus
        
        sends excitatory axons to the contralateral (right) cranial nerve VI nucleus (abducens nucleus)
        
        Motor axons from the abducens nucleus excite the lateral rectus muscle of the right eye
        
        Another excitatory projection from the abducens crosses the midline, back to the left side
        
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- - - - detect the force of gravity and tilts of the head
      - sensitive to different kinds of movement
        
        not!!! because their hair cells differ
        
        because of the specialized structures in which the hair cells reside.
      - 2 paired organs
        
        the saccule and the utricle :hole:
        
        large chambers near the center of the labyrinth
        
        Each otolith organ contains a macula (sensory epithelium) ♂️
        
        vertically oriented within the saccule (VS 🩲) and horizontally oriented within the utricle (UH…)
        
        detect changes of head angle ∠ + linear acceleration 🏃‍♂️ of the head
        
        contains hair cells 🛏️ 🧢
        
        above cap, tiny crystals of calcium carbonate called otoconia 🪨
        
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        each hair cell has one very tall cilium, called the kinocilium.
        
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    - - sensitive to head rotation
        
        Angular acceleration is generated by sudden rotational movements: primary stimulus for the semicircular canals.
        
        hair cells
        
        clustered within a sheet of cells, the crista 📄, located within a bulge along the canal called the ampulla 🗻
        
        cilia project into the gelatinous cupula
        
        when canal rotating about axis, endolymph exerts a force upon the cupula :boat:
        
        bows the cupula, which bends the cilia
        
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        All the hair cells in an ampulla have their kinocilia oriented in the same direction
        
        all get excited or inhibited together.
      - the three arcing structures of the labyrinth
        
        lie in approximately orthogonal planes 📐
        
        3 on each side of the head
        
        rotation excites the hair cells of one canal, & inhibits the hair cells of its contralateral partner’s canal.