07 Vestibular System (1)

07 Vestibular System (1) - LEARNING OBJECTIVES: THE...

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N-73 LEARNING OBJECTIVES: THE VESTIBULAR SYSTEM 1. Describe the anatomy and physiology of the otolith organs. 2. Describe the anatomy and physiology of the semicircular canals. 3. List the major structures in the central vestibular pathways. 4. List the eye movements produced by each of the six eye muscles. 5. Define “conjugate eye movements,” “saccades,” “smooth pursuit eye movements,” and “nystagmus.” 6. Identify the structures in the vestibuloocular reflex, and describe the mechanism of this reflex. 7. List three vestibular disorders.
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N-74 Robert W. Blair, Ph.D. THE VESTIBULAR SYSTEM Reading: Widmaier et al., Human Physiology, 12 th ed., pp. 218-220 I. Functions and General Physiology A. Proprioception: Conscious and unconscious sense of posture and balance by monitoring head movements B. Motor control: Adjust muscular contraction to maintain posture and balance C. Vestibuloocular reflex: Adjust eye movements so that visual target remains on retina in response to head movements D. General physiology: For the otolith organs and the semicircular canals, movement of the cilia ultimately changes the action potential firing frequency in vestibular neurons by a mechanism similar to that in the cochlea. II. Anatomy and Physiology of the Otolith Organs (Fig. 7-42, p. 218) A. Anatomy of the Otolith Organs: Utricle and Saccule 1. These structures are located near the center of the labyrinth. 2. See Fig. 2. Both structures are similar, and have a sensory epithelium called the macula which contains the hair cells. The cilia of the hair cells contain one long cilium with a bulbous end that is called a kinocilium along with multiple stereocilia . All cilia project into a gelatinous substance which contains otoliths . The otoliths are crystals of calcium carbonate . Head movement causes the otoliths to move due to the force of gravity, which causes the whole gelatinous mass to move, which moves the cilia and produces changes in neurotransmitter release from the hair cells. B. Physiology of the Otolith Organs 1. These organs detect linear acceleration and displacement of the head (e.g., tilting). Figure 1: Anatomy of vestibular apparatus.
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N-75 Figure 2: Anatomy of otolithic membrane. 2. Function (Figs. 7-45, p. 219; 7-46, p. 220) a. When the head moves and changes its angle, this results in a change in the force of gravity to the head. The change in gravity causes the otoliths to move. When they move, the gelatinous substance in which they are embedded also moves. This bends the cilia.
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07 Vestibular System (1) - LEARNING OBJECTIVES: THE...

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