Slide 1Slide 2Sensory organs share a common cellular basisSensory receptors convert stimulus energy to action potentialsSensory receptors convert stimulus energy to action potentialsSlide 6Sensory receptors convert stimulus energy to action potentialsSlide 8Specialized sensory receptors detect five categories of stimuliSpecialized sensory receptors detect five categories of stimuliSlide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18The inner ear houses our organs of balanceSlide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Artificial lenses can correct focusing problemsSlide 29Slide 30How color vision worksHow color vision worksHow color vision worksHow color vision worksSlide 35Slide 36Slide 37Slide 38Slide 39Slide 40Biology 003: Organisms in Their EnvironmentLecture #10 – The SensesSENSORY RECEPTIONSensory organs share a common cellular basisAll animal senses originate in sensory receptors, specialized cells or neurons that are tuned to the–conditions of the external world and–the internal organs.All sensory receptors–trigger an action potential and–send information to the central nervous system.Sensory receptors convert stimulus energy to action potentialsSensory receptors detect stimuli.In a process called sensory transduction, receptors–detect one type of signal (the stimulus) and–convert the signal to another type, an electrical signal.When you eat ice cream:1. sugar molecules enter the taste bud2. sugar molecules bind to sweet receptors- specific protein molecules embedded in a taste bud3. binding triggers a signal transduction pathway- some ion channels in the membrane close and others open4. changes in the flow of ions creates a receptor potential5. release of neurotransmitters initiates an action potentialSensory receptors convert stimulus energy to action potentialsFigure 29.2ASugarmoleculeSensoryreceptorcellsTasteporeTastebudSensoryneuronSugar molecule(stimulus)Membraneof a sensoryreceptor cellSweetreceptorSignaltransductionpathwayIonchannelsIonSensoryreceptorcellReceptorpotentialNeurotransmitterSensory neuronAction potentialto the brain543216No sugar Sugar presentRates of action potentialsmVThe stronger the stimulus…–the more neurotransmitter released by the receptor cell–the more frequently the sensory neuron transmits action potentials to the brain.Sensory receptors convert stimulus energy to action potentialsFigure 29.2B“Sugar” interneuronSugarreceptorcellTastebudBrainSensoryneuronsSaltreceptorcell“Salt” interneuronTastebudNo sugarNo saltIncreasing sweetness Increasing saltinessSpecialized sensory receptors detect five categories of stimuliThere are five categories of sensory receptors.1. Pain receptors detect dangerous stimuli including high heat and pressure.2. Thermoreceptors detect heat or cold.3. Mechanoreceptors respond to–touch–pressure–sound4. Chemoreceptors–include sensory receptors in our nose and taste buds–respond to chemicals5. Electromagnetic receptors respond to –electricity–magnetism–light (sensed by photoreceptors)Specialized sensory receptors detect five categories of stimuliFigure 29.3AHeat Light touchEpidermisPain ColdHairDermisNerveto brainHairmovementStrongpressureSensory Receptors in Human SkinHEARING AND BALANCE© 2012 Pearson Education, Inc.Figure 29.4AOuter earInner earAuditorycanalEardrumMiddle earEustachiantubeNerve to brainFigure 29.4BSkull bonesSemicircular canals(function in balance)Auditorynerve,to the brainCochleaEardrumStirrupAnvilHammerCochleaFigure 29.4DHair cellsTectorial membraneSensoryneuronsTo the brain via the auditory nerveBasilarmembraneOrgan of CortiFluid-filled area of the CochleaPressure waves transmitted to the fluid of the cochlea–Bending of hair cells in the organ of Corti facilitated by the tectorial and basilar membranes–trigger nerve signals to the brain.The ear converts air pressure waves to action potentials that are perceived as soundDeafness is the loss of hearing.Deafness can be caused by the inability to detect sounds resulting from–middle-ear infections–a ruptured eardrumDeafness–can also result from damage to sensory receptors–is often progressive and permanent.The ear converts air pressure waves to action potentials that are perceived as soundThe inner ear houses our organs of balanceThe semicircular canals in the inner ear detect body position and movement. –detect changes in the head’s rotation or angular movement.SemicircularcanalsNerveCochleaSacculeUtricleFlow of fluidCupulaFlowof fluidCupulaHairsHaircellNerve fibersDirection of body movementVISIONEVOLUTION CONNECTION: Several types of eyes have evolved independently among animalsThe ability to detect light plays a central role in the lives of nearly all animals.All animal light detectors are based on cells called photoreceptors that contain pigment molecules that absorb light.Humans have single-lens eyes that focus by changing position or shapeThe outer surface of the human eyeball is a tough, whitish layer of connective tissue called the sclera.–At the front of the eye, the transparent cornea–lets light into the eye–also helps focus light.–The iris is a pigmented layer in the anterior eye, which gives the eye its color; creates size of pupilFigure 29.7CScleraCiliary muscleLigamentCorneaIrisPupilAqueoushumorLensVitreoushumorBlind spotArteryand veinOpticnerveFovea(center ofvisual field)RetinaChoroidHumans have single-lens eyes that focus by changing position or shapeThe lens and ciliary body divide the eye into two fluid-filled chambers.1. The large chamber behind the lens is filled with a jellylike vitreous humor.2. The smaller chamber in front of the lens contains the thinner aqueous humor.Humans have single-lens eyes that focus by changing position or shapeThe lens focuses light onto the retina by bending light rays.In mammals, the lens focuses by changing shape using–muscles and ligaments that suspend the lens.Figure 29.8Ciliary muscle contractedLigaments slackenLight from a near object(diverging rays)Near vision (accommodation)CorneaScleraLensCiliary muscle relaxedLigaments pull on lensLight from a distant object(parallel rays)Distance visionRetinaChoroidArtificial lenses can correct focusing problemsThree vision problems are common.1. Nearsightedness is the inability to focus on distant objects, usually caused by an eyeball that is too long.2. Farsightedness is the inability to focus on close