Sensory Systems
-
Upload
deborah-powers -
Category
Documents
-
view
27 -
download
9
description
Transcript of Sensory Systems
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
Tortora Tortora
Page 266Page 266
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.
Tortora Tortora
Page 266Page 266
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
Tortora Tortora
Page 266Page 266
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.
Tortora Tortora
Page 266Page 266
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
Tortora Tortora
Page 266Page 266
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.
Tortora Tortora
Page 266Page 266
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
Tortora Tortora
Page 266Page 266
ReceptorReceptorss
• ClassificatioClassification based on n based on location:location:–ExteroceptorExteroceptorss
–VisceroceptoVisceroceptorsrs
–ProprioceptoProprioceptorsrs
Tortora Tortora
Page 266Page 266
ReceptorsReceptors• Classification Classification based on type based on type of stimulus:of stimulus:– MechanoreceptoMechanoreceptorr
– ThermoreceptorThermoreceptor– NociceptorNociceptor– ElectromagnetiElectromagnetic receptorc receptor
– ChemoreceptorChemoreceptor
Tortora Tortora
Page 266Page 266
ReceptorsReceptors
•ClassificaClassification based tion based on type of on type of complexitycomplexity::–SimpleSimple–ComplexComplex
Tortora Tortora
Page 266Page 266
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.
TortoraTortora
Page 266-Page 266-267267
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
TortoraTortora
Page 197Page 197
Structures Structures of the Eyeof the Eye
• Eye has three Eye has three layers.layers.–Fibrous tunicFibrous tunic–Vascular tunicVascular tunic–Nervous tunicNervous tunic
TortoraTortora
Page 266-Page 266-267267
Structures Structures of the Eyeof the Eye
•Fibrous Fibrous tunic tunic consists consists of:of:–ScleraSclera–CorneaCornea–ConjunctivaConjunctiva
TortoraTortora
Page 266-Page 266-267267
Structures Structures of the Eyeof the Eye
•Vascular Vascular tunic tunic consists ofconsists of–ChoroidChoroid–Ciliary Ciliary bodybody
–irisiris
TortoraTortora
Page 266-Page 266-267267
Structures Structures of the Eyeof the Eye
• Nervous Nervous tunic tunic consists ofconsists of–RetinaRetina–Rods & conesRods & cones–Detached Detached retinaretina
TortoraTortora
Page 266-Page 266-267267
Structures Structures of the Eyeof the Eye
•LensLens–SuspensorSuspensory y ligamentsligaments
–cataractscataracts
TortoraTortora
Page 266-Page 266-267267
Structures Structures of the Eyeof the Eye• Anterior Anterior CavityCavity– Anterior Anterior chamberchamber
– Posterior Posterior chamberchamber
– Aqueous humorAqueous humor– Intraocular Intraocular pressurepressure
– GlaucomaGlaucoma
TortoraTortora
Page 266-Page 266-267267
Structures Structures of the Eyeof the Eye
•Posterior Posterior CavityCavity–Filled Filled with with vitreous vitreous humorhumor
TortoraTortora
Page 266-269Page 266-269
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
TortoraTortora
Page 268-269Page 268-269
Photoreceptors
• Modified dendrites.
• Highly specialized.– Rods– Cones
TortoraTortora
Page 268-269Page 268-269
PhotoreceptoPhotoreceptorsrs
• Modified Modified dendrites.dendrites.
• Highly Highly specialized.specialized.– ConesCones– Cones are Cones are concentrated concentrated around the around the central central fovea.fovea.
TortoraTortora
Page 268-269Page 268-269
TortoraTortora
Page 268-Page 268-269269
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.
TortoraTortora
Page 271-Page 271-272272
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.
TortoraTortora
Page 271-Page 271-272272
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
TortoraTortora
Page 271-Page 271-272272
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.
TortoraTortora
Page 271-Page 271-272272
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.
TortoraTortora
Page 271-Page 271-272272
Stimulation of Stimulation of PhotoreceptorsPhotoreceptors
TortoraTortora
Page 271-Page 271-272272
• 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.