Y khoa - Dược - Chapter 35: Special senses

35Special SensesLearning Outcomes (cont.)35.1 Describe the anatomy of the nose and the function of each part. 35.2 Describe the anatomy of the tongue and the function of each part. 35.3 Describe the anatomy of the eye and the function of each part, including the accessory structures and their functions. Learning Outcomes (cont.)35.4 Explain the visual pathway through the eye and to the brain for interpretation.35.5 Describe the causes, signs and symptoms, and treatments of various disorders of the eyes.35.6 Describe the anatomy of the ear and the function of each part, and the role of the ear in maintaining equilibrium. Learning Outcomes (cont.)35.7 Explain how sounds travel through the ear and are interpreted in the brain.35.8 Describe the causes, signs and symptoms, and treatments of various disorders of the ears.Introduction Special senses – receptors in the headNose Tongue Eyes Ears Touch is a generalized sense Stimulus  nervous system  brain   responseThe Nose and the Sense of SmellOlfactory receptorsChemoreceptors – respond to changes in chemical concentrationsChemicals must be dissolved in mucusLocated in the olfactory organThe Nose and the Sense of Smell (cont.)The information is sent along olfactory bulbs and tracts Cerebrum – interprets information as a type of smell Activation of smell receptors  information sent to olfactory nervesSensory AdaptionApply Your KnowledgeANSWER: After a few minutes, smell receptors undergo sensory adaptation and no longer respond to the chemical, and the patient can no longer smell the odor. You notice an odor coming from a patient when you enter the exam room. Why would the patient not be able to smell it?Very Good!The Tongue and the Sense of TasteGustatory receptors – on the taste budsTaste buds Papillae of the tongueRoof of mouthWalls of throatTongue} fewer than on tongue The Tongue and the Sense of Taste (cont.)Taste buds Taste cells ~ chemoreceptors that react to chemicals in food and drink must be dissolved in saliva to activate Supporting structures ~ fill in spaceTongueThe Tongue and the Sense of Taste (cont.)Taste sensations Sweet – tip Sour – sides Salty – tip and sidesBitter – back Umami 5th basic taste GlutamateSpicy foodsActivate pain receptorsInterpreted by brain as “spicy”TongueBackThe Tongue and the Sense of Taste (cont.)Activation of taste cellsCranial nervesGustatory cortex of cerebruminterprets information as a particular tasteTaste sensationApply Your KnowledgeWhat are the four primary taste sensations and where are their corresponding taste cells located?ANSWER: The four primary taste sensations are: Sweet – concentrated on the tip of the tongueSour – concentrated on the sides of the tongueSalty – concentrated on the tip and sides of the tongueBitter – concentrated on the back of the tongueGreat Job!The Eye and the Sense of SightVision systemEyesOptic nervesVision centers in the brainAccessory structuresEye Processes light to produce imagesThree layersTwo chambersSpecialized partsThe Eye and the Sense of Sight (cont.)Outer LayerSclera Tough outer layerLight cannot pass through the scleraSense receptors Limbus ~ corneal-scleral junctionCornea Transparent “Window” that allows light into eyeEyeThe Eye and the Sense of Sight (cont.)Middle layer – choroid Contains blood vesselsIrisMuscle tissue relaxes and contracts to alter the size of the pupilRegulates the amount of light entering the eyeEyeThe Eye and the Sense of Sight (cont.)Middle layer (cont.) Ciliary body ~ wedge-shaped muscles that controls the shape of the lensLens Changes shape to focus light on retinaAccommodation – the ability of the lens to change shapeEyeThe Eye and the Sense of Sight (cont.)Inner layer – retinaOptic disc – optic nerve enters retinaRods Sensitive to light Function in dim light – “night” and peripheral visionDo not provide sharp image or detect colorEyeThe Eye and the Sense of Sight (cont.)Inner layer (cont.)ConesFunction in bright lightSensitive to color and provide sharp imagesEnable differentiation of tones and hues of colorThe Eye and the Sense of Sight (cont.)Anterior chamber of the eyeFront of lensFilled with aqueous humor – nourishes and bathes anterior eyePosterior chamber Behind lensContains vitreous humor – maintains shape of eyeball and keeps the retina flatEyeLensBackRetinaChoroidCN II (Optic)Optic discSclera Vitreous chamber (posterior chamber)Pupil Limbus Iris Cornea Anterior chamberAnterior PosteriorCiliary body Visual Accessory OrgansEye orbits – form a protective shell around the eyesEyebrows protect eyesVisual Accessory OrgansEyelids Skin, muscle, and connective tissueBlinking Prevents surface from drying outKeeps foreign material out of eyeVisual Accessory Organs (cont.)Conjunctivas – produce mucus to keep the surface of the eyeball moistLacrimal apparatusLacrimal glands ~ produce tearsNasolacrimal ducts ~ drain tears into noseVisual Accessory Organs (cont.)Extrinsic eye musclesSix per eye Move the eyeLevator palpebrae superioris (cut)Optic NerveInferior RectusTrochlea Superior obliqueSuperior rectusLateral rectusInferior oblique Apply Your KnowledgeMatching:___ Middle layer of eye A. Lacrimal glands___ Eye sockets B. Aqueous humor___ Controls shape of lens C. Retina___ Outer layer of eye D. Sclera___ Anterior chamber E. Vitreous humor___ Tears F. Ciliary body___ Ability of lens to G. Choroid change shape H. Orbits___ Posterior chamber I. Accommodation___ Inner layer of eye IHFEDCBAGANSWER:Visual PathwaysEye works like a cameraLight enters the eye through the lensRefraction – bending of light to focus it on the retinaProjected upside down on the retinaOpticchiasmVisual PathwaysOpticnerveOccipital lobe ofcerebrumRetina convertslight to nerve impulseImage upside down on retinaImage turned right-side upApply Your KnowledgeWhat is refraction and which part of the eye carries out refraction?ANSWER: Refraction is the bending of light that enters the eye to focus it on the retina. The cornea performs this function.Well done!The Aging EyeTears alteredEyes dryerLens more rigidRetinal changes Less adaptable to lightImpaired night and peripheral vision Impaired depth perceptionCommon Diseases and DisordersDisorder/DiseaseDescription AstigmatismCornea or lens has abnormal shape; blurred images Dry eye syndromeResults from a decreased production of the oil within the tearsEctropinEversion of lower eyelidCommon Diseases and DisordersDisorder/DiseaseDescription EntropionInversion of lower eyelidNystagmusRapid, involuntary eye movementsRetinal detachmentLayers of retina separate; medical emergencyApply Your KnowledgeWhat vision changes can occur in the elderly patient?ANSWER: An elderly patient may have difficulty seeing because of drooping eyelids. Focusing may be more difficult because less light enters the eye. He may have difficulty distinguishing colors due to yellowing of the lens. Vision may be fuzzy because of changes in the retina. Night vision can become impaired. The patient may see floaters or “sparks.”Nice job!The Ear and Senses of Hearing and EquilibriumExternal earAuricle (pinna) - collects sound wavesExternal auditory canalLined with hairs and glands that produce cerumenGuides sound wave to the tympanic membrane which separates external ear and middle earEarThe Ear and Senses of Hearing and Equilibrium (cont.)Middle earEar ossiclesMalleusIncusStapesOssicles Vibrate Hit the oval windowEarThe Ear and Senses of Hearing and Equilibrium (cont.)Middle ear (cont.)Eustachian tubeConnects middle ear to throatEqualizes pressure on eardrumOval window – separates middle ear from inner earEarAuricle (pinna)External EarMiddle Ear Inner Ear External ear canalTympanic membrane Oval window OssiclesStapesIncusMalleusLabyrinthVestibule Cochlea Eustachian tube Back The Ear and Senses of Hearing and Equilibrium (cont.)Inner ear – labyrinth of communicating chambersSemicircular canals ~ equilibriumVestibule ~ equilibrium CochleaHearing receptors Organ of Corti – organ of hearingInner earSemicircular canals CochleaOval window Vestibule Cochlear nerve Back The Ear and Senses of Hearing and Equilibrium (cont.)Head movementActivates equilibrium and hearing receptorsVestibular nerves transmit information Cerebrum interprets information and advises the body to make adjustmentsApply Your KnowledgeMatching: ___ Pinna A. Organ of Corti___ Malleus, incus, and stapes B. Cerumen___ Hearing receptors C. Ear ossicles___ Inner ear D. Tympanic membrane___ Organ of hearing E. Auricle___ Earwax F. Cochlea___ Eardrum G. Labyrinth___ Detect balance of body H. Semicircular canalsHGFDCBAEANSWER:Supear!The Hearing ProcessExternal earCollect sound wavesChannels waves to the tympanic membraneTympanic membrane vibratesMiddle ear – ossicles amplify vibrationsThe Hearing Process (cont.)Inner earAmplified waves bend hairs lining cochleaMovement of hairs trigger nerve impulsesImpulses are transmitted by auditory nerve to the brain for interpretationThe Hearing Process (cont.)Bone conductionAlternate sound pathway to inner earBones of the scull conduct sound wavesIdentification of hearing problemsNormal bone conductionProblem likely in middle or external ear Apply Your KnowledgeHow do we hear?ANSWER: Sound waves are collected by the external ear and are funneled down the ear canal to the tympanic membrane. The waves make the tympanic membrane vibrate. The ossicles amplify these vibrations which enter the inner ear and cause movements of the hairs that line the cochlea. These movements trigger nerve impulses which are sent to the brain via the auditory nerve. The brain perceives the impulses as sound.Great Answer!The Aging EarExternal ear LargerCerumen drierCanal narrowsMiddle earEardrum shrinksJoints between ossicles degeneratesInner ear – less sensitive to position changesHow to Recognize Hearing Problems in InfantsInfants to 4 monthsStartled by loud noisesRecognize mother’s voice4 to 8 monthsRegularly follow soundsBabble at people8 to 12 monthsRespond to the sound of their nameRespond to “no”Common Diseases and Disorders of the EarDisorder/DiseaseDescriptionAcoustic NeuromaBenign tumor of the cranial nerve involved in hearing and balance; commonly causes gradual hearing loss in one earCerumen impactionBuild up of wax within external auditory canal with some degree of hearing loss due to blocked sound wavesCommon Diseases and Disorders of the EarDisorder/DiseaseDescriptionHearing lossDeafness; the loss of the ability to hear sounds at normal levels. Conductive – blockage of sound wavesSensorineural – damage to auditory nerveCommon Diseases and Disorders of the Ear (cont.)Disorder/DiseaseDescriptionOtitis Otitis externa Otitis media Otitis internaInflammation of the ear Swimmers’ earMiddle ear infection; common infectionLabyrinthitis; inner ear infectionOsteosclerosisImmobilization of the stapes; common cause of conductive hearing lossPresbycusisHearing loss due to aging processApply Your KnowledgeTrue or False:___ Otitis media is also called swimmers’ ear.___ Presbycusis is hearing loss due to the aging process.___ Otitis interna is an inflammation of the labyrinth.___ Otosclerosis is the immobilization of the stapes. Conductive hearing loss is caused by damage to the  auditory nerve. Labyrinthitis often causes nausea and vertigo.TTTFANSWER:externaExcellent!Sensorineural FTIn Summary35.1 Olfactory receptors – the sense receptors for the sense of smell – are found in the olfactory organ located in the upper part of the nasal cavity. 31.2 Gustatory receptors are found on the taste buds, which are located on the papillae (bumps) of the tongue.In Summary35.3 The eye is composed of three layers. The sclera is the outer protective layer and includes the cornea. The middle vascular layer is the choroid consisting of the iris, pupil, ciliary body, and lens, and is the area of light regulation and focusing. The innermost layer is the retina containing the rods and cones, the optic nerve, and the optic disk. This is where the nerve impulse is picked up and brought to the brain for interpretation. The accessory organs are the orbits, eyelids, conjunctivas, lacrimal apparatus, and extrinsic eye muscles, all of which are protective for the eye. In Summary (cont.)35.4 The cornea, lens, and fluids focus light on the retina. The retina converts the image into nerve impulses that the optic nerve transmits to the brain for interpretation.35.5 There are many common diseases and disorders of the eyes with varied signs, symptoms, and treatments. Some of these include astigmatism, dry eye syndrome, ectropion, entropion, nystagmus, and retinal detachment.In Summary (cont.)35.6 There are three parts to the ear. The external ear includes the auricle or pinna and the external auditory canal to the tympanic membrane. The middle ear begins at the tympanic membrane and ends at the oval window and includes the ear ossicles. The inner ear is composed of the labyrinth and contains the organ of Corti as well as perilymph and endolymph – the fluids of hearing. The semicircular canals and vestibule in the inner ear function in the body’s equilibrium and balance, sending impulses to the vestibular nerves, which bring information to the cerebrum for interpretation.In Summary (cont.)35.7 The outer ear collects sound waves and channels them to the tympanic membrane, which vibrates. The vibrations are amplified by the ear ossicles and enter the inner ear and cochlea. The movements of the hairs in the cochlea trigger nerve impulses that the auditory nerve transmits to the brain.35.8 There are many common diseases and disorders of the ears with varied signs, symptoms, and treatments. Some of these include acoustic neuroma, cerumen impaction, hearing loss, otitis, otitis externa, otitis media, otitis interna, otosclerosis, and presbycusis.Every closed eye is not sleeping, and every open eye is not seeing. ~ Bill CosbyEnd of Chapter 35