Sensation Overview 1. Specialized sensory cell (receptor) detects a physical or chemical change. 2....
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SensationOverview
1. Specialized sensory cell (receptor) detects a physical or chemical change.
2. The physical or chemical change causes action potentials in sensory neurons.
3. Sensory neurons carry action potentials throughcranial nerves or spinal nerves to the CNS.4. Typically the sensory information is carried to thethalamus where synapses occur.5. Neurons transmit sensory information from the thalamus to a specific region of the cerebrum wherethe sensation is experienced.
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Example: vision
1. Rods and Cones(receptors) in the retina of the eye detect light.
2. Sensory neurons in retina begin producing action potentials
3. Action potentials are carried out of the eye through the optic nerve.
4. Optic nerve enters the brain and leads to the thalamus.
5. Neurons are stimulated in the thalamus and transmit action potentials to specific locations in the occipital lobe.
1. Light from the environment enters the eyes and strikes the retina.
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Receptors in retina
Sensory Neurons
Synapse in Thalamus
Projection toThe Cerebrum
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Types of Sensory Receptors (often modified nerve endings)
Chemoreceptors (tongue, nasal epithelium)
Pain Receptors (respond to chemicals released when tissue is damaged)
Thermoreceptors (temperature of skin and at the hypothalamus)
Mechanoreceptors (proprioceptors in muscles and joints, hearing, balance)
Photoreceptors (detect light - eye)
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Visceral Pain - referred pain
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Lacrimal gland
Lacrimal sac
Nasolacrimalduct
Eye video
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sclera
Choroid layer
Retina(fovea)
Optic disc
Posterior chamber(vitreous humor)
lens
Ciliary body
iris
Anterior chamber (aqueous humor)
corneaconjunctiva
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Functions of Key Parts of the Eye
Iris: dilates and constricts thereby regulating the amount of light that enters to posterior chamber of the eye.
Ciliary body: muscular – pulls on suspensory ligaments and causes the lens to bend and change focus.
Fovea centralis: area having the densest amount of photoreceptors
Optic Disk (blind spot): area on retina where neurons leave and form optic nerve. No photoreceptors are found here.
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Structure of the Retina
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Receptors in retina
Sensory N
eurons
Synapse in T
halamus
Projection to
The
Cerebrum
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HEARING: System that converts the pressure changes in air intoChanges in action potential frequencies.
When something vibrates, it causes the air to move back and forth.This generates “sound waves” which are slight increases and decreases Local air pressure.
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Auricle(pinna)
Auditory canaltympanum
malleus
incus
stapes
Semicircular canal
cochlea
Auditory tube(Eustachian tube)
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tympanun
Oval window
Round window
Function of the Ear
When air waves strike the tympanum, the malleus, incus and stapes move. The stapes presses up against the oval window causing fluid to move within the cochlea. The movement of the fluids is eventually detected by sensory cells within the cochlea.
The cochlea contains sensory cells that provide our perception of hearing
Hair cells in the cochlea detect the movement of fluids in the cochlea
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The cochlea contains receptor cells that detect sound.
At the base of the semicircular canals we find receptor cells that detect dynamic equilibrium (changes in movement in the sagittal, coronal and transverse plains)
In each case, “hair cells” are the receptor cells. These cells detect fluid movements in the inner ear and transduce these fluid movements into action potentials.
cilia
Sensory nerve fiber
Current flow
Hearing video
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To detect motion, sensory cells (hair cells) detect movement of fluids within the semicircular canals
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Nasal cavity
Cribiform plate of ethmoid bone
Olfactory cells
Olfactory bulb
The Sense of Smell