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Lecture 13

BGYB30H3 Lecture 13 Notes Autonomic and Somatic Control-Oct 22

Biological Sciences
Course Code
Ingrid L.Stefanovic

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BGYB30H3 Lecture 13 Notes
-the pinna and ear canal direct sound into the ear
-sound waves hit the tympanic membrane (ear drum)
-malceus, incus, and stapes are bones in the middle ear that amplify the sound waves and
conduct them
-stapes connects to the oval window of the inner ear
-inner ear is filled with fluid and contains the cochlea, vestibular apparatus, and semicircular
-cochlea is used in perception of sounds
-vestibular apparatus and semicircular canals are used for equilibrium
-the higher the pitch, the higher the frequency
-the larger the amplitude, the louder the sound
-sound wave first hits eardrum and turns into a vibration
-vibration travels through middle ear where it can be amplified
-vibration is converted into fluid waves at oval window
-fluid wave pushes on the tectoral membrane of cochlear duct where hair cells are found
-when hair cells are activated, neurotransmitter is released on sensory neurons
-action potentials are transmitted along cochlear nerve to the thalamus
-cochlea contains fluid called perilymph, which is similar to extracellular fluid
-cochlear duct contains endolymph fluid, which is similar to intracellular fluid
-cochlea contains vestibular, tympanic, and cochlear duct
-cochlear duct is found between the tectoral and basilar membrane
-organ of corti contains hair cells that bend when tectoral membrane bends
-fluid waves bend the hair cells
-fluid waves passing through vestibular duct create oscillations
-hair cells are non-neural receptor cells that contain stereocilia arranged in height
-kinocillium is the longest stereocilia and the tip links connect stereocilia
-movement of stereocilia generates signal transduction
-tonic signal is sent by sensory neuron at rest
-increased excitability causes more ion channels to open and an increased frequency of action
potentials in the cochlear nerve
-when hair cells bend in opposite direction, inhibition occurs
-high pitch sounds stimulate the thick part of the basilar membrane of the cochlear duct
-low pitch sounds stimulate the tail of the basilar membrane
-vestibular cochlear nerve (cranial nerve XIII) projects to the cochlear nuclei of the medulla
where it may crossover, then goes to the pons, thalamus, and finally the auditory cortex
-equilibrium requires sight, proprioceptors and inner ear
-dynamic and static components of equilibrium in the inner ear
-dynamic is the motion of the body and static is the body position relative to gravity
-saccule and utricle of the vestibular apparatus sense linear rotation and head position
-semicircular canals sense rotational acceleration in different directions
-posterior monitors head moving from side to side like a cartwheel
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