2 IntroductionSensory receptors - make it possible for the body to respond to stimuli caused by changes occurring in the internal or external environmentDifferent types of receptors respond to different stimuliGeneral function—responds to stimuli by converting them to nerve impulsesSensationsSensory adaptation - receptor potential decreases over time in response to a continuous stimulusReceptors for special senses of smell, taste, vision, hearing, and equilibrium are grouped into localized areas or into complex organs
3 Receptors and sensations Types of receptorsChemoreceptors activated by amount or changing concentration of certain chemicals; e.g., taste and smellPain receptors - Nociceptors—activated by intense stimuli that may damage tissue; the sensation produced is painThermoreceptors — activated by changes in temperatureMechanoreceptors activated when “deformed” to generate receptor potentialProprioceptors -Location limited to skeletal muscle, joint capsules, and tendonsProvide information on body movement, orientation in space, and muscle stretchPhotoreceptor— found only in the eye; respond to light stimuli if the intensity is great enough to generate a receptor potential
4 Somatic senses Touch and pressure Free ends of dendrites Called nociceptorsReceptors for painMeissner’s corpusclessense touchlarge and superficialPacinian corpusclesRespond to deep pressure/stretchDeep dermis and joint capsulesStretch receptorsFound in tendons and musclesOnce stretched, the muscle shortens
5 Temperature sensesOrgans of Ruffini - also called Ruffini’s corpusclesDeep in dermisSense heat degreesBulbs of Krause - sense cold
6 Sense of pain Free nerve endings Visceral pain Referred painPain nerve fibers - Chronic/acuteRegulation of pain impulse - awareness of pain - thalamus. Impulse conducted to cerebral cortex - judges intensity and location of pain.Endorphins provide natural pain control.Serotonin inhibits release of pain impulses in spinal cord.
7 Special senses - receptors are in specialized organs Smell - olfactory senseTaste - gustatory senseHearing - auditory senseStatic equilibrium - balance when stationaryDynamic equilibrium - balance when movingSight - sense of vision
9 Sense of smell Olfactory receptors Cilia in nasal cavitychemoreceptorsOlfactory organs - epithelial supporting tissueNerve pathwaysAction potential to olfactory nerves in olfactory bulbThalamic and olfactory centers in brain
11 Sense of taste Taste receptors - chemoreceptors Taste sensations Taste hairs portrude from taste poresChemicals dissolved in salivaTaste sensationsSweetSourSaltBitterNerve pathwaysFacial, glossopharyngeal, vagus nerves to medulla oblongata to gustatory cortex in cerebrum.
13 Sense of hearing External ear Middle ear Inner ear - Auricle or pinna - visible - collects soundExternal auditory meatus - tubeMiddle earin temporal bone- contains ossiclesMalleus - attached to tympanic membraneIncus - attached to malleus and stapesStapes - attached to chochleaInner ear -semicircular canals - equilibriumCochlea - hearingOrgan of corti - located in the cochlear duct. Contains supporting cells and hair cells
14 Sense of hearing Nerve pathways - sound waves move tympanic membrane Movement of membrane moves ossicles which move oval window which create waves which bend hairs.Hearing - stimulation of auditory area in cerebral cortex.Range of hearing 20-20,000 decibels, whisper 40 db, rock concert 120 db, pain, 140 db
16 Sense of equilibrium - two types Static equilibrium—ability to sense the position of the head relative to gravity or to sense acceleration or decelerationDynamic equilibrium—needed to maintain balance when head or body is rotated or suddenly moved; able to detect changes both in direction and rate at which movement occurs
17 Static Equilibrium Stability of head when body is motionless Utricle and Saccule - location for static equilibrium senseMacula - movement provides information about head positionOtoliths located in macula, gravity shifts them, bending hair cells.Nerve fibers send message to brainBody is restored to normal position.
18 Dynamic equilibrium Cristae ampullaris, located in semicircular canal Cupula - gelatinous cap in which hairs are embedded, moves with flow of endolymph (fluid)Semicircular canals placed at right angles - detect motion in all directionsWhen cupula moves, hair cells are bent, sending action potential to medulla oblongata and then other areas for interpretation.
20 Visual accessory organs Eyelid - palpebraevoluntary muscle and skin, lined with mucous membrane called conjunctiva.Eyelashes and eyebrows - give some protection agains foreign objects entering eyeLacrimal gland -secret tears. Tears are drained from surface of eyeball.
21 Extrinsic muscles of the eye Attach to outside of eyeball and bones of the orbit
22 Structure of the eye Outer tunic Middle tunic Cornea - transparent portion that lies over the iris.Sclera - tough outer coatMiddle tunicChoroid coat - vascular and pigmentedCiliary body - attaches to irisIris - colored part of the eyeLens - held in place by suspensory ligaments and ciliary muscles. Has elasticity - shape is adjustable.
23 Inner tunic and cavities/chambers Retina - innermost coat of eyeballContains receptorsMacula luteaFovea centralisOptic diskCavities - anterior and posterior chamberAnterior cavity contains anterior/posterior chambersFilled with aqueous humor - watery fluid - involved in bending lightPosterior cavity - right behind lens.Filed with Vitreous humor - semisolid, maintains intraocular pressure.
25 Light refraction and the process of seeing Refraction - Light waves bentAccomplished by cornea, lens, aqueous humorAccomodation of the lens - increase in curvature for near vision.Pupil constricts controlling the entering of light
26 Visual receptors - undergo changes that generate nerve impulses Rods - black and white visionRhodopsin - photo pigmentBreaks down into opsin and retinalEnergy is required to reform rhodopsinCones - color visionThree types
27 Visual Pigments Rhodopsin Isodopsin Opsin, retinal Erythrolabe - red Chlorolabe - greenCyanolabe - blue
28 Visual nerve pathways Optic nerves Optic chiasma cross over Thalamus Visual cortex of occipital lobe