1. Vestibular Anatomy & Function NBIO 401 – Monday November 4, 2013

2. Objectives: -Be able to describe the structure of the two components of the vestibular system, the semicircular canals and the otoliths. -Be able explain how the structure of the semicircular canals and the position and orientation of the hair cells in the ampulla allow the canals to transduce head rotation into neural signals. -Be able explain how the structure of the otoliths and the position and orientation of the hair cells in the saccule and utricle transduce head tilt and linear acceleration into neural signals. -Be able to describe the pathway from the vestibular labyrinth in the periphery to the vestibular nuclei, including the locations of neuron cell bodies and axon terminations.

3. Objectives: -Be able to describe the structure of the two components of the vestibular system, the semicircular canals and the otoliths. -Be able explain how the structure of the semicircular canals and the position and orientation of the hair cells in the ampulla allow the canals to transduce head rotation into neural signals. -Be able explain how the structure of the otoliths and the position and orientation of the hair cells in the saccule and utricle transduce head tilt and linear acceleration into neural signals. -Be able to describe the pathway from the vestibular labyrinth in the periphery to the vestibular nuclei, including the locations of neuron cell bodies and axon terminations.

4. Objectives: -Be able to describe the structure of the two components of the vestibular system, the semicircular canals and the otoliths. -Be able explain how the structure of the semicircular canals and the position and orientation of the hair cells in the ampulla allow the canals to transduce head rotation into neural signals. -Be able explain how the structure of the otoliths and the position and orientation of the hair cells in the saccule and utricle transduce head tilt and linear acceleration into neural signals. -Be able to describe the pathway from the vestibular labyrinth in the periphery to the vestibular nuclei, including the locations of neuron cell bodies and axon terminations.

5. Objectives: -Be able to describe the structure of the two components of the vestibular system, the semicircular canals and the otoliths. -Be able explain how the structure of the semicircular canals and the position and orientation of the hair cells in the ampulla allow the canals to transduce head rotation into neural signals. -Be able explain how the structure of the otoliths and the position and orientation of the hair cells in the saccule and utricle transduce head tilt and linear acceleration into neural signals. -Be able to describe the pathway from the vestibular labyrinth in the periphery to the vestibular nuclei, including the locations of neuron cell bodies and axon terminations.

6. Vestibular Labyrinth: -semicircular canals -otoliths

8. SEMICIRCULAR CANALS

9. HOLLOW HOOP (CANAL)

10. HOLLOW HOOP (CANAL) WIDER CHAMBER IN CANAL (AMPULLA) SEMICIRCULAR CANALS

11. (ROTATION)

12. OTOLITHS (TILT & ACCELERATION) SEMICIRCULAR CANALS (ROTATION)

13. OTOLITHS (TILT & ACCELERATION) SEMICIRCULAR CANALS (ROTATION)

14. Semicircular Canals (ROTATION)

15. HOLLOW HOOP (CANAL) WIDER CHAMBER (AMPULA) SEMICIRCULAR CANALS

20. AMPULA

23. UTRICLE

29. Position of semicircular canals in the skull

30. Otoliths (TILT, ACCELERATION)

31. OTOLITHS (TILT & ACCELERATION)

32. OTOLITHS (TILT & ACCELERATION)

35. Kinocillium (longest process; at one side)

36. Kinocillium (longest process; at one side) Stereocilia (all shorter processes)

37. Otoliths HAIR CELLS IN OTOLITHS

38. Otoliths HAIR CELLS IN OTOLITHS

39. Otoliths HAIR CELLS IN OTOLITHS

43. Bending processes toward kinocillium DEPOLARIZES

44. Bending away from kinocillium HYPERPOLARIZES

63. Copyright ©2004 American Physiological Society Fitzpatrick, R. C. et al. J Appl Physiol 96: 2301-2316 2004; doi:10.1152/japplphysiol.00008.2004 Orientation of the maculae of the utricle and saccule

64. Copyright ©2004 American Physiological Society Fitzpatrick, R. C. et al. J Appl Physiol 96: 2301-2316 2004; doi:10.1152/japplphysiol.00008.2004 Orientation of the maculae of the utricle and saccule

65. Central Connections of the Vestibular Labyrinth

67. Pathway from the canals and otoliths to the brain is via axons whose cell bodies are in a ganglion (called Scarpa’s ganglion or the vestibular ganglion).

68. Scarpa’s Ganglion (vestibular ganglion)

69. May 9, 1752 – October 31, 1832

70. Carlo Beolchin (Scarpa’s student)

71. Museo per la storia dell ‘Universita de Pavia

72. Museum for the history of the University of Pavia

74. Museo per la storia dell ‘Universita de Pavia Museum for the history of the University of Pavia

75. Scarpa’s Ganglion (vestibular ganglion)

76. V inferior cerebellar peduncle vestibular nuclei VIIIth nerve VIIIth nerve inferior cerebellar peduncle The proximal end of the axons of neurons in Scarpa’s ganglion terminate in the vestibular nuclei.

77. Vestibular nuclei project to: 1)spinal cord 2)oculomotor nuclei 3) reticular formation 4)cerebellum 5)thalamus

78. Normally, the cupula has neutral buoyancy in endolymph that surrounds it. Alcohol is less dense than water (see demo to right). When you drink, alcohol enters the blood, and then into the cupula. The cupula becomes less dense. It floats in the endolymph more. The cupula bends a little more than usual away from the ground. This bends hair cells, as if you are rotating, even when you are still. This gives you the sensation of rotating when you are still, i.e., you get the dreaded spins. Alcohol and Dizziness Blue H 2 O cubes float in water (left) but sink in alcohol (right)

79. the end