Sensory systems

Stimulation-stimulus impinges on a sensory receptor transduction: energy from a sstimulus transformed into a graded potential in the associated sensory(afferent) neuron Transmission: AP develops in axon of sensory neuron and it conduction to CNS Interpretation: All nerve impulses are qualitatively alike, perception of stimulus is product of brain 6 classes of receptors: thermoreceptors Nociceptors Electromagnetic receptors Mechanoreceptors Chemoreceptors photoreceptors

sensitive to temp changes -in vertebrates, most thermoreceptors are in the dermis -Pit vipers(rattlesnakes) use thermoreception for the detection of prey. These organs are wired to the visual processing of the brain

impulses perceived as pain -pain can be viewed as an adaptive mechanism to warn the body about damage Overstimulation can also send signals as pain

sense eletric and magnetic fields -all animals generate electric currents from contraction of their muscles. water is a good conduction of electricity, and thus many fish have the trait to detect electric fields

touch, pressure, and body position -several types of Mechanoreceptors detect mechanical distortions (touch) -specialized sensors in skeletal muscle provide the body with feedback about body position Vibrations, hearing, balance -Lateral line in fish- allows fish to sense objects that reflect pressure waves and vibrations hearing fish-otoliths in the head of fishes vibrate against hair cells. otoliths much denser than water Terrestrial animals- a tympanic membrane (ear drum) vibrates in response to sound waves

EAr drum vibrates, bones of inner ear (Malleus, incus, and stapes-evolved from bones in early mammalian jaw). oval window is the entrance to the cochlea to auditory nerves. The eustachian tube is behind the eardrum, helps eardrum regulate pressure 1) vibration of the ear drum causes the bones of the inner ear to move: sound is amplified and transmitted to the oval window 2)oscillations of the oval window cause fluid in cohclea to move. Hair within cochlea vibrate and bend, sending impulses to sensory neurons- loudness -depends on how many hair cells stimulated. frequency- is determined by location in cochlea where fibers in the basilar membrane resonate

oscillations of the oval window cause fluid in cohclea to move. Hair within cochlea vibrate and bend, sending impulses to sensory neurons- loudness -depends on how many hair cells stimulated. frequency- is determined by location in cochlea where fibers in the basilar membrane resonate -fibers vary in length and stiffness (short/stiff near the base of the cochlea) long/flexible near the apex. High frequency sounds resonate with short fibers, low with longer

low goes farther high doesnt travel as far

Overcomes the problem of determining the location of sounds. speed of sound is a constant. location can be determined by the time is takes for the echo to return

location along cohlea where hair cells in the basilar membrane resonate in response to sound the wavelength

Labyrinth of inner ear is a fluid-filled membranous chamber with semicircular canals Linear motion- acceleration distorts the matric, causing hair cells to bend and stimulating sensory neurons Angular motion- semicircular canal loops in a different plane at the end of the semi canals are swollen chambers called ampullae withing this are hair cells.

contains proteins that bind with particular chemicals in the environment, causing depolarization of sensory neurons. -terrestrial vertebrates use their tongue to taste smell- specialized for detecting airborne particles, insects use antennae

sensory cells that detect electromagenetic wabes -some animals have eyes that can detect light without forming an image (scallops, flatworms, seastarts) -annelids, mollusks, antrohpods, vertebrades have evolved image-formining eyes. Compounds-insect creating mosiac camera type- focus light onto retina to have conitous imge

contains rods- detect lo levels of light. hundreds may be on single nerve cell cones- detect color when light there is enough light

region of keenest vision contains only cones in diurnal vertebrates nocturnal animals often lack cones, black and white vision