LS 2 Lec 9 Sensory
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Transcript of LS 2 Lec 9 Sensory
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Life Sciences 2
Sensory Systems
Chapter 41
Dr. Joseph Esdin
Sensory Cells
Sensory cells transduce physical or
chemical stimuli into action potentials
Receptor cells
Modified neurons
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Types of Receptors
Photoreceptors
Mechanoreceptors
Chemoreceptors
Thermoreceptors
Nociceptors
Electroreceptors
Magnetoreceptors
Mechanoreceptors & Sound
Sound is the vibration of air molecules
Waves of vibrations can have
High amplitude (loudness)
Frequency (pitch)
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Anatomy of the EarOuter Middle Inner
Pinna
Auditory canal
Tympanic membrane
Oval windowRound window
Cochlea
Auditory nerve
MalleusIncus
Stapes
How Is Sound Transmitted?
Vibration of air molecules goes through
the pinna, passing through the external
auditory canal
The waves then vibrate the tympanic
membrane which causes the three
ossicles to move
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How Is Sound Transmitted?
The ossicles cause the oval window to
vibrate
This leads to stimulation of hair cells
inside the cochlea
The Cochlea
Cochlea
Auditory nerve
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The Cochlea
Auditory nerve
Scala
vestibuli
Cochlear duct
(endolymph)
Scala
Tympani
Organ of Corti
Organ of Corti
Hair cells Tectorial membrane
Basilar membrane AxonsTo auditory nerve
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Hair CellStereocilia Kinocilium
Sensory neuron
Stretch gated channels
Hair Cell
Hair cellBasilar membrane
Tectorial membrane
Cochlear nerve
Stereocilia
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Hair Cells At Rest
Stretch gated channels
Protein bridgeK+
Ca2+
Voltage gatedcalcium
channels
K+
K+
NT
K+
Hair Cells Depolarized
Stretch gated channels
Protein bridge
K+
Ca2+
Voltage gatedcalcium
channels
K+
K+
NT
K+
Ca2+
Ca2+
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Hair Cells
Movement of the stereocilia towards the
kinocilium activates the stretch activated
channels
Movement of the stereocilia away from
the kinocilium closes the stretch
activated channels
Neural Pathway of Hearing
Cochlear nerve fibers synapse on
neurons in the cochlear nuclei in the
medulla oblongata
The signal is then sent to the thalamus
From the thalamus, the information
travels to the auditory cortex of thetemporal lobe
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The Eyes
Composed of an optical portion
Focus the image on sensory cells
Transform the image to the brain
through series of action potential
Have receptors that are sensitive to light
Layers of the Eyes
Fibrous
VascularNeural
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Fibrous Layers
Cornea
Sclera
Vascular Layer
Choroid
Zonular fibers
Ciliary muscles
Iris
Pupil
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Vascular Layer
Choroid
Pigmented layer that contain blood vessels
Ciliary muscles
Zonular fibers
Hold the lens in place
Iris
Accommodation
The ciliary muscles allow objects to be
focused on the retina no matter how
near or distant they are
The lens can change shape
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AccommodationCiliary muscles relaxed
Ciliary muscles contracted
Lens flat to focus distant objects
Lens thick to focus near objects
Zonular fibers are pulled
Zonular fibers are loose
Iris
Dim light
Bright light
Radial smooth muscles
Circular smooth muscles
Pupil
radial smooth musclescontract, pupil dilates
circular smooth musclescontract, pupil is constricts
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Neural Layer
Retina
Retina
The retina contains photoreceptors to
receive the light and send it to the brain
through the optic nerve
Contains the fovea centralis (high visual
acuity)
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Retina
Have different types of cells
Ganglion cells
Amacrine
Bipolar
Horizontal
Photoreceptors (rods and cones)
Retina
Light
Ganglion cells
Amacrine
Bipolarcells
Horizontal Rod
Cones
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Photoreceptor
Rods
Sensitive to light
Respond to low illumination
Cones
Less sensitive to light
Respond to high illumination
Both types of photoreceptors containpigments that absorb light
Pigments
Rods
Rhodopsin
Cones
S, M, and L pigments
Photopsin
These proteins contain a pigment called________
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Rods in the DarkcGMP levels are high
Na+channels are open
Na+influx causes depolarization
Ca2+channels open
Ca2+Influx occurs
NT release causes graded
potential in bipolar cells
Rods
Bipolar cells
Na+
K+
Ca2+
Rods
Membrane
Rhodopsin
Retinal
Transducin
Phosphodiesterase! " # !
cGMP Breakdown
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Rods When Exposed to Light
Rods
Bipolar cells
When cGMP levels are low
Na+channels are closed
Hyperpolarization occurs
No NT release
No graded potential
Neural Pathway of Vision
Nasal retina
Temporal retina
Optic nerve
Visual cortex
Optic chiasm
Optic tract
Left visual field Right visual field
Binocular vision
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Neural Pathway of Vision
The two optic nerves meet to form theoptic chiasm
Some axons cross to the opposite sideof the brain forming optic tracts
Fibers pass to the thalamus
Signals are sent from the thalamus to
the visual cortex