Transcript Senses
Get the Sensation! Aps reaching the brain via sensory neurons are sensations Interpretation of the sensation by the brain is perception http://www.exploratorium.edu/exhibits/f_exh ibits.html http://dogfeathers.com/java/hyperstar.html# getstarted Some facts……. Aps are the same no matter what type of stimulus causes them Sensory receptors stimulate Aps by converting energy to an AP-this is sensory transduction The ability to distinguish these Aps depends on what part of the brain receives them The transduction threshold varies with conditions & genetics Steps in Sensory Transduction Sensory Systems Sensory receptors are neurons specialized to detect a stimulus Categorized based on the type of stimulus they respond to Mechanoreceptors-movement, pressure, tension • Skin, ears, nociceptors in joints Photoreceptors-variations in light • eye Chemoreceptors-chemicals • Nose, tongue Thermo receptors-changes in temp • Hypothalamus,skin Pain receptors-tissue damage • Throughout body Electromagnetic receptors • Visible light, electricity, magnetism Photoreceptors Eye cups/eye spots Intensity/location of light Invertebrate eyes Compound eyes-insects & crustaceans • Each eye consists of several thousand ommatidia • Mosaic image, extremely good at detecting movement & color Single-lens eyesspiders, mollusks • Similar to camera Vertebrate Eye Sclera-thick, protective outer layer, connective tissue Becomes transparent cornea in front of eye, allows light in Conjunctiva(mucous membrane) covers sclera & keeps eye moist-doesn’t cover cornea Choroid-layer just underneath sclera Pigmented, forms iris in front of eye Hole in center of iris is pupil-iris controls amount of light entering pupil Highly vascularized Vert. Eye cont… Retina-just inside choroid-innermost layer Contains photoreceptor cells(rods & cones) All rods & cones connect to optic disc at back of retina which carries impulse to brain • No photoreceptor cells here-blind spot Lens & ciliary body Lens transparent protein disc that focuses images by changing shape • Flat for close objects, spherical for distant objects Ciliary muscles control shape of lens Aqueous humor-fluid between cornea & lens Vitreous humor-fluid behind lens-fills most of eye Photoreceptor cells Rods More sensitive to light, no color distinction Night vision, black & white Fovea-area of retina w/ greatest density of rods Cones Need more light to be stimulated, excellent color distinction Day vision Relative numbers differ in nocturnal & diurnal animals Rhodopsin Visual pigment in rods & cones • Consists of retinal pigment & opsin protein • Light triggers a shape change responsible for generating action potential Mechanoreceptors-Hearing The ear converts mechanical energy into electrochemical energy of action potential(mechanoreceptors) External ear(pinna)-collects sound waves Tympanic membrane(ear drum)-transmits vibrations to middle ear bones Vibrations are passed to incus(anvil), then malleus(hammer), then stapes(stirrup), which transmits them to oval window Oval window transmits to cochlea, which contains fluid and the organ of corti, with tiny hair cells embedded in it As fluid of cochlea moves, hair cells tap against tectorial membrane-this causes an action potential to be generated which is transmitted to auditory nerve Auditory nerve carries AP to temporal lobe of brain Volume of sound is determined by amplitude (height) of sound wave Louder sound = more vibrations =more Aps Pitch is determined by frequency of the waves Higher frequency = higher-pitched sound Balance Detected by mechanoreceptors(hair cell) in the inner ear Balance Utricle and saccule detect head position using calcium crystals, hair cells, and gravity Semicircular canals detect head movement using fluid and hair cells Taste and Smell Both taste buds and olfactory cells (nose) are chemoreceptors