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Auditory systems
1.Use mechanoreceptors to convert pressure waves to receptor potentials
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Fires an action potential
- 1.Stretch receptors:Ionotropic
- 2.Olfaction:metabotropic
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Don't fire action potentials
- 1. Hearing:Ionotropic
- -releases neurotransmitter
- 2.Vision:metabotropic
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what do pinnaedo?
collect sound waves and direct them to the auditory canal
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what does the Tympanic membrane cover and why does it vibrate?
- 1.Covers the end of the auditory canal
- 2.Vibrates in response to pressure waves
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Middle ear
- 1.Air filled cavity
- 2.Equilibrates air pressure between middle ear and the outside
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by what does the middle open to the throat?
the Eustachian tube
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Ossicles
- 1.Malleus, incus, stapes
- 2.Transmit vibrations of tympanic membrane to the oval window of the cochlea
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Inner ear
1.Fluid filled cavity
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Inner ear canals
- 1.Vestibular system: for balance
- 2.Cochlea: for hearing
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Cochlea
- 1 Tapered and coiled chamber composed of three parallel canals separated by
- -Reissner's membrane
- -Basilar membrane
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Three canals of Cochlea
- 1.Upper and lower
- -have high Na+ concentrations, move vibrations
- 2.Middle
- -have high K+ concentration, filled with endoli
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Round window
- 1.Flexible membrane at the end of the canal
- -relieves pressure
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Organ of Corti
- 1.Transduces pressure waves into action potentials
- 2.Contains hair cells with stereocilia
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where does the organ of Corti sit?
on the basilar membrane
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what can the hair cells in the organ of Corti do?
- 1.They bend and create a graded potential that alter neurotransmitter release
- 2.Translate physical force to something nervous system can use
- 3.Outer hairs: not important
- 4.Inner hairs: these translate physical force into transmitter
- release in the auditory nerve
- 5.Mechanorecpetors, but do not fire action potentials, release neurotransmitters
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what causes basilar membrane to move?
1.Vibration
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Action potentials stimulated by mechanoreceptorsat different positions along organ of Corti aretransmitted to the brain via....
the auditory nerve
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Conduction deafness
1.Loss of function of tympanic membrane or ossicles
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When you activate the basilar membrane....
- 1.Sound pressure moves from the upper cana of the cochlea
- 2.travels down through the lower canal
- 3.relieves pressure through the round window
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Nerve deafness
- 1.Damage to inner ear or auditory nerve pathways
- 2.Hair cells in the organ of Corti can be damaged by loud sounds
- 3.Damage is cumulative and irreversible
- Ex.Loud music
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Hair cells
1.Mechanoreceptors in organs of hearing and equilibrium
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Bending of stereocilia can_____or_____ion channels
open or close
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Hair cells: the plasma membrane can be depolarized or hyperpolarized
- 1.K+ flows through stereocilia to depolarize cells
- 2.Ca+ rushes in, causes transmitter release
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Rhodopsins
pigment all animals use
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Photorecpetor cells
Metabotropic sensory cells that transform light into action potentials
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Light travels to the retina...
- 1.optic nerve
- 2.Ganglion cells(first cells to fire action potential)
- 3.Photoreceptors
- 4.Pigmented epithelium
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Rod cells have
- 1.Outer segment
- -discs of plasma membrane containing rhodopsin to capture photons
- -where light is translated
- 2.Inner segment
- -contains the nucleus and organelles
- 3.Synaptic terminal
- -wherethe rod cell communicates with other neurons
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Rhodopsin
- -Molecule consists of:
- 1. opsin(a protein)
- 2. a light-absorbing group, 11-cis-retinal
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where do Rhodopsin molecules sit?
in plasma membrane of a photoreceptor cell
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When 11-cis-retinal absorbs photons lights......
- -Changes to the isomer all-trans-retinal
- -Changes the conformation of opsin
- How it works:
- 1. Transducin gets activated by rhodopsin
- 2.Binds and activates PDE, which changes cGMP to GMP
- -Dark room: depolarizes and opens Na+ and Ca2+channel
- -light hits eye: hyperpolarizes and closes channel ,cGMP can bind
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Bleaching
in vertebrate eyes, the retinal and opsin eventually separate
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Rod cell
- 1.Type of vertebrate photoreceptor
- 2.Modified neuron that does not produce action potentials
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Membrane potential of rod cell
- 1.No light = -35mV
- 2.With light = hyperolarizes the rod cell, less transmitter
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Cells that are responsible for night vs color vision
- 1.Rod cells:Night vision
- 2.Cone cells: color vision
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In dark, whats happening with sodium and calcium?
- 1. lots of sodium and calcium are flowing into the cell
- 2.cyclic GMP is bonded tochannels
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In light, what is happening with transducin?
- 1.Transducin activates PDE
- 2. PDE convertscGMP to GMP
- 3. Na+ channels close
- 4.Membrane is hyperpolarized
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Foeva
area where cone cell density is highest
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color blindness
Loss of function of one or more types of cone cells
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How many types of cone cells do humans have?
3
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How many layers of neurons does the retina have?
5
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What forms the optic nerve?
Axxons from ganglion cells
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how are photoreceptor cells connected to ganglion cells?
via bipolar cells
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When the rod is in the dark, cells dump....
glutamate(excitatory transmitter)
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Horizontal cells
form synapses with bipolar cells and phtoreceptors
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Amacrine cells
form local synapses with bipolar cellsand ganglion cells
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Light activates ____bipolar cells
- 1. ON bipolar cells
- -metabotropic
- -depolarize in light
- -hyperpolarize in dark
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Dark activates _____bipolar cells
- 1. OFF bipolar cells
- -ionotropic
- -depolarize in dark
- -hyperpolarize in light
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