sensory systems
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Sensory Systems. How many different sensory receptors are hard at work during a roller coaster ride?. Tortora Page 266. Sensations. Definition: State of awareness of internal or external conditions of the body. Tortora Page 266. Sensations. Four conditions for a sensation to occur: - PowerPoint PPT PresentationTRANSCRIPT
Sensory Sensory SystemsSystems
How many different How many different sensory receptors are sensory receptors are hard at work during a hard at work during a roller coaster ride? roller coaster ride?
SensationsSensations
• Definition:Definition:–State of State of awareness of awareness of internal or internal or external external conditions conditions of the bodyof the body
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Sensations
• Four conditions Four conditions for a sensation for a sensation to occur:to occur:– Threshold Threshold stimulus.stimulus.
– A receptor to A receptor to pick up the pick up the stimulus.stimulus.
– Conduction of Conduction of impulse.impulse.
– Translation by Translation by brain into brain into sensation.sensation.
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Sensations• Stimulus Stimulus
results in a results in a generator generator potential.potential.– Depolarization Depolarization of receptor of receptor membrane.membrane.
– Follows afferent Follows afferent pathway to pathway to thalamus.thalamus.
– From thalamus, From thalamus, action potential action potential goes to cerebrumgoes to cerebrum
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Molecules in food stimulate Molecules in food stimulate generator potentials in generator potentials in
taste budstaste buds
SensatioSensationsns
• 4 Characteristics of a 4 Characteristics of a sensation.sensation.–ProjectionProjection
•““connects” sensation in cerebrum to connects” sensation in cerebrum to correct part of body.correct part of body.
•Example: Brain knows that you just Example: Brain knows that you just burned the tip of burned the tip of
the pinky the pinky finger on the finger on the left hand.left hand.
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Sensations
• 4 Characteristics of a 4 Characteristics of a sensation.sensation.–AdaptationAdaptation
•Decrease in sensitivity with Decrease in sensitivity with continued non threatening continued non threatening stimulation.stimulation.
•Example: A person living near the Example: A person living near the railroad tracks railroad tracks
sleeps sleeps through the through the passing of the passing of the train train
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Sensations
• 4 Characteristics of a 4 Characteristics of a sensation.sensation.–AfterimagesAfterimages
•Sensation persists even though Sensation persists even though stimulus is removed.stimulus is removed.
•Exampe:Exampe: You look at a bright You look at a bright object. object. It remains as a It remains as a vision for a vision for a period of period of time after looking time after looking away. away.
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SensationsSensations
• 4 Characteristics of a 4 Characteristics of a sensation.sensation.–ModalityModality
•Type of stimulation.Type of stimulation.
•Example:Example: Vision Vs smell Vs Vision Vs smell Vs touchtouch
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ReceptorReceptorss
• ClassificatioClassification based on n based on location:location:–ExteroceptorExteroceptorss
–VisceroceptoVisceroceptorsrs
–ProprioceptoProprioceptorsrs
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ReceptorsReceptors• Classification Classification based on type based on type of stimulus:of stimulus:– MechanoreceptoMechanoreceptorr
– ThermoreceptorThermoreceptor– NociceptorNociceptor– ElectromagnetiElectromagnetic receptorc receptor
– ChemoreceptorChemoreceptor
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ReceptorsReceptors
•ClassificaClassification based tion based on type of on type of complexitycomplexity::–SimpleSimple–ComplexComplex
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Accessory Accessory Structures of the Structures of the
EyeEye• EyelidsEyelids• EyebrowsEyebrows• Lacrimal Lacrimal apparatusapparatus
• Lacrimal glandLacrimal gland• Lacrimal Lacrimal canals.canals.
• Nasolacrimal Nasolacrimal duct.duct.
• Role of Role of lysozyme: lysozyme: antibacterial.antibacterial. Lacrimal apparatus from Gray’s Lacrimal apparatus from Gray’s
AnatomyAnatomy
Structures Structures of the Eyeof the Eye
•Eye lies Eye lies within a within a cavity cavity called the called the orbit.orbit.
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Structures Structures of the Eyeof the Eye
• Muscles that Muscles that move the eye:move the eye:– Inferior Inferior rectusrectus
– Lateral Lateral rectusrectus
– Superior Superior rectusrectus
– Medial rectusMedial rectus– Inferior Inferior obliqueoblique
– Superior Superior obliqueoblique
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Structures Structures of the Eyeof the Eye
• Eye has three Eye has three layers.layers.–Fibrous tunicFibrous tunic–Vascular tunicVascular tunic–Nervous tunicNervous tunic
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Structures Structures of the Eyeof the Eye
•Fibrous Fibrous tunic tunic consists consists of:of:–ScleraSclera–CorneaCornea–ConjunctivaConjunctiva
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Structures Structures of the Eyeof the Eye
•Vascular Vascular tunic tunic consists ofconsists of–ChoroidChoroid–Ciliary Ciliary bodybody
–irisiris
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Structures Structures of the Eyeof the Eye
• Nervous Nervous tunic tunic consists ofconsists of–RetinaRetina–Rods & conesRods & cones–Detached Detached retinaretina
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Structures Structures of the Eyeof the Eye
•LensLens–SuspensorSuspensory y ligamentsligaments
–cataractscataracts
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Structures Structures of the Eyeof the Eye• Anterior Anterior CavityCavity– Anterior Anterior chamberchamber
– Posterior Posterior chamberchamber
– Aqueous humorAqueous humor– Intraocular Intraocular pressurepressure
– GlaucomaGlaucoma
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Structures Structures of the Eyeof the Eye
•Posterior Posterior CavityCavity–Filled Filled with with vitreous vitreous humorhumor
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Structure of Structure of the Retinathe Retina
• Retina covers Retina covers the choroid the choroid layer.layer.
• Consists of Consists of three zones of three zones of neuronsneurons– photoreceptorsphotoreceptors– BipolarBipolar– Ganglion Ganglion neuronsneurons
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Photoreceptors
• Modified dendrites.
• Highly specialized.– Rods– Cones
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PhotoreceptoPhotoreceptorsrs
• Modified Modified dendrites.dendrites.
• Highly Highly specialized.specialized.– ConesCones– Cones are Cones are concentrated concentrated around the around the central central fovea.fovea.
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Visual PathwayVisual Pathway
• Generator Generator potential is potential is created by created by rods and rods and cones.cones.
• Bipolar Bipolar neuronsneurons
• Ganglion Ganglion neurons.neurons.
• Optic nerve Optic nerve II.II.
3rd order 3rd order neuron.neuron.
Formation of Formation of Image on Image on RetinaRetina
• Four processes Four processes are needed to are needed to form an image form an image on the retina.on the retina.
• FirstFirst– Extrinsic Extrinsic
muscles cause muscles cause convergence of convergence of eyes on object.eyes on object.
– Depth Depth perception.perception.
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Formation of Formation of Image on Image on RetinaRetina
• SecondSecond– Pupils Pupils constrict constrict so as to so as to center the center the light light entering entering the eye.the eye.
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Formation of Formation of Image on Image on RetinaRetina
• ThirdThird– Refraction Refraction
(bending of (bending of the light the light rays) occurs rays) occurs due to;due to;• CorneaCornea• Aqueous humorAqueous humor• LensLens• Vitreous humorVitreous humor
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Formation of Formation of Image on Image on RetinaRetina
• FourthFourth– AccomodatioAccomodation - the n - the lens lens changes changes shape so as shape so as to focus to focus image on image on the retina.the retina.
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Stimulation of Stimulation of PhotoreceptorsPhotoreceptors
• Photopigments are Photopigments are molecules that change molecules that change structure when struck structure when struck by lightby light
• Small amounts of light Small amounts of light cause rhodopsin to cause rhodopsin to break down.break down.
• Results in opsin and Results in opsin and retinal A.retinal A.
• Starts generator Starts generator potential.potential.
• Reforms quickly.Reforms quickly.• Daylight overwhelms Daylight overwhelms
rods.rods.
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Stimulation of Stimulation of PhotoreceptorsPhotoreceptors
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• Three types of conesThree types of cones– Red Red – GreenGreen– BlueBlue
• Each contains a Each contains a different photoreceptor.different photoreceptor.
• All need abundance of All need abundance of lightlight
• All break down with All break down with intense light but intense light but quickly reform.quickly reform.
• Most common form of Most common form of color blindness is lack color blindness is lack of red or green cones.of red or green cones.