LS2:Sensory Systems part 2
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1.Use mechanoreceptors to convert pressure waves to receptor potentials
Fires an action potential
- 1.Stretch receptors:Ionotropic
Don't fire action potentials
- 1. Hearing:Ionotropic
- -releases neurotransmitter
what do pinnaedo?
collect sound waves and direct them to the auditory canal
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
- 1.Air filled cavity
- 2.Equilibrates air pressure between middle ear and the outside
by what does the middle open to the throat?
the Eustachian tube
- 1.Malleus, incus, stapes
- 2.Transmit vibrations of tympanic membrane to the oval window of the cochlea
1.Fluid filled cavity
Inner ear canals
- 1.Vestibular system: for balance
- 2.Cochlea: for hearing
- 1 Tapered and coiled chamber composed of three parallel canals separated by
- -Reissner's membrane
- -Basilar membrane
Three canals of Cochlea
- 1.Upper and lower
- -have high Na+ concentrations, move vibrations
- -have high K+ concentration, filled with endoli
- 1.Flexible membrane at the end of the canal
- -relieves pressure
Organ of Corti
- 1.Transduces pressure waves into action potentials
- 2.Contains hair cells with stereocilia
where does the organ of Corti sit?
on the basilar membrane
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
what causes basilar membrane to move?
Action potentials stimulated by mechanoreceptorsat different positions along organ of Corti aretransmitted to the brain via....
the auditory nerve
1.Loss of function of tympanic membrane or ossicles
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
- 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
1.Mechanoreceptors in organs of hearing and equilibrium
Bending of stereocilia can_____or_____ion channels
open or close
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
pigment all animals use
Metabotropic sensory cells that transform light into action potentials
Light travels to the retina...
- 1.optic nerve
- 2.Ganglion cells(first cells to fire action potential)
- 4.Pigmented epithelium
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
- -Molecule consists of:
- 1. opsin(a protein)
- 2. a light-absorbing group, 11-cis-retinal
where do Rhodopsin molecules sit?
in plasma membrane of a photoreceptor cell
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
in vertebrate eyes, the retinal and opsin eventually separate
- 1.Type of vertebrate photoreceptor
- 2.Modified neuron that does not produce action potentials
Membrane potential of rod cell
- 1.No light = -35mV
- 2.With light = hyperolarizes the rod cell, less transmitter
Cells that are responsible for night vs color vision
- 1.Rod cells:Night vision
- 2.Cone cells: color vision
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
In light, what is happening with transducin?
- 1.Transducin activates PDE
- 2. PDE convertscGMP to GMP
- 3. Na+ channels close
- 4.Membrane is hyperpolarized
area where cone cell density is highest
Loss of function of one or more types of cone cells
How many types of cone cells do humans have?
How many layers of neurons does the retina have?
What forms the optic nerve?
Axxons from ganglion cells
how are photoreceptor cells connected to ganglion cells?
via bipolar cells
When the rod is in the dark, cells dump....
form synapses with bipolar cells and phtoreceptors
form local synapses with bipolar cellsand ganglion cells
Light activates ____bipolar cells
- 1. ON bipolar cells
- -depolarize in light
- -hyperpolarize in dark
Dark activates _____bipolar cells
- 1. OFF bipolar cells
- -depolarize in dark
- -hyperpolarize in light
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