5 5 2014 CHAPTER 47 Animal Sensory Systems PPT Notes sensory abilities correlate w the environment a species lives in its mode of life animals detect 5 changes in environment sensory receptors CNS effectors 1 smell 2 sound 3 sight 4 pressure 5 temperature s environmental s detected via 1 transduction converts external stimulus to internal in form of action potentials along sensory neuron 2 amplification of signal 3 transmission of single to CNS sensory organs convey info to brain o sensory neuron specialized receptor cell forms synapse w sensory neuron highly specific each type of sensory neuron sends signal to specific portion of brain different regions specialize for interpreting various stimulu types of sensory receptors nociceptors sense harmful stimuli ex tissue injury thermoreceptors sense temperature mechanoreceptors sense pressure i e statocyst of crab sack filled w fluid lined w pressure receptor cells also contains Ca2 rich substance that rests on bottom sends action potential to brain when flipped bumped against receptor cells used to detect in hearing physical pressure on skin muscle blood vessel movement chemoreceptors sense presence of specific molecules photoreceptors sense particular light wavelengths electroreceptors sense electric fields magnetoreceptors sense magnetic fields sensory transduction sensory cell receptor s light sound tension stimuli into an electrical signal potential in potential lets different types of stimuli transduced to a common signal type that can be interpreted by the brain in o o o o o large in membrane potential of sensory receptor firing rate of action potentials sent to brain resting state inside of plasma membrane more than exterior depolarization of membrane ion flow s interior to become more hyperpolarization of membrane ion channel s cause cell interior to become more than resting amt of depolarization hyperpolarization of sensory receptor proportional to intensity of stimulus 5 5 2014 mechanoreceptors pressure causes ion channels to open close o o ions flow in out depolarization hyperpolarization vertebrates ion channels found in hair cells pressure receptor cells transduce sound waves to electrical signals stereocillium microvilli made of actin filaments outgrowths of hair cells kinocillium the tallest cilium on hair cells that extends into fluid chambers depolarization of hair cell makes Ca2 ions move in process 1 in neurotransmitter release synapse btwn hair cell sensory neuron 2 postsynaptic cells are excited fire action potential to brain afferent neurons in PNS affected 3 PNS conveys info to CNS Hyperpolarization inhibits action potential o mammalian ear transduces sound waves into action potentials sends info to brain structure outer ear middle ear inner ear each separated by a membrane outer ear collects pressure waves funnels into ear canal amplication factor of 22 pressure waves hit tympanic membrane eardrum separating outer from inner ear 15 times larger than oval window factor of vibration by 15 amplify vibrations from tympanic membrane tympanic membrane vibrates w same frequency as sound waves passes vibrations to ear ossicles 3 ear ossicles vibrate against one another stapes last ossicle vibrates against oval window membrane separating mid inner ear oval window makes waves in fluid within cochlea detects sound frequency cochlea divided into 3 fluid filled chambers via membranes hair cells form rows in middle cochlea chamber bottom of hair cell connects to basilar membrane o basilar membrane varies in stiffness frequencies cause membrane to vibrate maximally in specific spots hair cell stereocilia bends narrow part of basilar is stiff vibrates to high frequencies wide part of basilar is flexible vibrates to low frequencies o hair cells in particular places on membrane respond to certain frequencies different pitches stereocilia of hair cells touch smaller tectorial membrane hairs within cochlea sense pressure waves brain learns through experience which frequency combinations represent certain sounds hearing the ability to sense sound which is waves of pressure in air water frequency of pressure waves that occur in 1 second pitches different perceptions of sound frequency humans hearing is not acute 20 Hz 20k Hz elephants use infrasounds bats use ultrasonic sounds to echolocate o lateral line system in fishes amphibians detects pressure in water lateral line canal system contains hair cells kinocilia stereocilia in hair cells bend w water pressure produces action potential in sensory neurons to brain information abt pressure specific points along head body photoreception light sensing o o organs vary from light sensitive eyespots to image forming eyes in insects compound eyes composed of hundreds thousands of light sensing columns called ommatidia ommatidium has lens that focuses light onto 4 receptor cells that send axons to CNS each ommatidium contributes information about singular small piece of visual field 5 5 2014 compound eye believed to have evolved in arthropod ancestor insects crustaceans etc o o in vertebrae cephalopod mollusks camera simple eye focuses incoming light onto layer of receptor cells photoreceptors vertebrae eyes structure composed of sclera cornea iris pupil lens retina sclera eye white cornea transparent sheet of connective tissue in front of sclera iris colored round muscle inside cornea that expands contracts to control amt of light entering eye pupil hole in center of iris lens struck by light passing through pupil after entering eye through cornea retina light focused onto by cornea lens made of 3 synapsing cell layers photoreceptors light sensitive form layer back of retina bipolar cells intermediate layer of connecting neurons ganglion cells form front innermost layer of retina axons project to CNS via optic nerve photoreceptors made of rods cones rods cones have stacks of membranes containing rhodopsin complex rhodopsin transmembrane protein complex made of one opsin molecule one retinal molecule retinal molecules within rhodopsin are pigments that shape when absorbing photon in opsin s conformation from cis to trans different stream of action potentials sent to brain rods sensitive to dim light not to colors dominate most of retina electrical activity across membrane neurotransmitter release maximized in dark cones sensitive to colors not to dim light blind spot photoreceptor free area where optic nerve leaves retina fovea small spot in center of retina made of only cones cephalopod
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