Principles of Animal PhysiologySlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Principles of Animal PhysiologyNervous SystemPrinciples of Animal PhysiologyNervous System▪Sensory cells - specialized cells for obtaining information about the environment.▸Review♦Mechanically gated channels♦Voltage-gated channels♦Chemically gated channels–ChemotaxisPrinciples of Animal PhysiologyNervous System▪Three primary roles of sensors▸Exteroreceptors♦Detect external signals such as light, chemicals, etc♦Somesthetic sensation - from body surface♦Special senses - vision, hearing, taste, and smell▸Interoreceptors♦Detect internal body signals such as blood pressure▸Proprioceptors♦Detect the animal’s position in spacePrinciples of Animal PhysiologyNervous System▪Perception - interpretation of the external world as created by the brain from nerve impulses delivered by sensory receptors.▪.Our perception of the world is incomplete, why?Principles of Animal PhysiologyNervous System▪Our perception of the world is incomplete, because:▸We (humans) can detect only a limited number of energy forms▸We perceive sounds, colors, shapes, textures, smells, tastes, deformations, and temperature▸We DO NOT perceive magnetic forces, electrical forces, polarized light waves, or ultraviolet light waves▸Information we receive is filtered or modified♦At the receptor, brainstem or cortex♦The brain can hide or distort the truthPrinciples of Animal PhysiologyNervous System▪The brain fills in and add lines to “complete” the picture (story).Principles of Animal PhysiologyNervous SystemPrinciples of Animal PhysiologyNervous SystemPrinciples of Animal PhysiologyNervous System▪Receptor Physiology▸Stimulus - change detectable by the body▸Modality - form of energy that stimuli take▸Receptor - structure that respond to a particular modality▸Transduction - conversion from one form of energy to another▸Adequate stimulus - modality with the lowest energy that would activate the receptor▸Doctrine of specific nerve energies (Johannes Muller) - receptors would only respond to certain stimulus and not to others▸Sensation perceived depends on receptor activated, not stimulusPrinciples of Animal PhysiologyNervous System▪Categories of receptor by type of energy used▸Photoreceptors - light▸Mechanoreceptors - mechanical energy▸Chemoreceptors - specific chemicals▸Thermoreceptors - change in temperature▸Nociceptors - pain, noxcious stimuli▸Electroreceptors - electrical fields▸Magnetoreceptors - magnetic fieldsPrinciples of Animal PhysiologyNervous System▪Uses of information detected by receptors▸Used for controlling efferent output▸Used as input to the reticular activating system for arousal and consciousness▸Gives rise to the animal’s perception of the environment▸May be stored for future usePrinciples of Animal PhysiologyNervous System▪A receptor may be either:▸A modified nerve ending♦Local change in membrane permeability♦Generator potential▸Another cell closely associated with the sensory neuron♦Stimulation causes changes in permeability of receptor cell♦Receptor potentialPrinciples of Animal PhysiologyNervous System▪Receptor vs generator potentialsPrinciples of Animal PhysiologyNervous System▪Receptors vary according to their speed of adaptation▪Adaptation - diminished response to sustained stimulus strength▸Tonic receptors♦Do not adapt at all, or adapt slowly–E.g. Muscle stretch receptors▸Phasic receptors♦Adapt rapidly♦Exhibit “on” “off” responses–E.g. Touch to the skinPrinciples of Animal PhysiologyNervous System▪Tonic and phasic receptorsPrinciples of Animal PhysiologyNervous System▪The Pacinian corpusclePrinciples of Animal PhysiologyNervous System▪Sensory Adaptation▸May take place in the PNS or CNS♦Receptor may act as a filter♦Transducer molecules may be depleted♦Enzyme cascade activity may be inhibited♦Electrical properties may change♦Spike initiation zone may be less sensitive♦Adjustments at higher brain centers may occurPrinciples of Animal PhysiologyNervous System▪Somatosensory pathway is “labeled” according to modality and location▸From receptor to brain perception area (somatosensory cortex)♦Receptor♦First order neuron (sensory/afferent neuron)♦Second order neuron♦Third order neuron♦And so on▸From a specific location to a specific portion of the cortex▸From a specific receptor/modality to a specific location on cortexPrinciples of Animal PhysiologyNervous System▪Photoreception: Eyes and Vision▸It may be the most dominant sense▸Uses photopigments▸Conversion of light energy to action potentials▸From eyespots to pinhole eye to camera eye to compound eyePrinciples of Animal PhysiologyNervous System▪Development of invertebrate eyePrinciples of Animal PhysiologyNervous System▪The mammalian eyePrinciples of Animal PhysiologyNervous System▪Control of light entering the eyePrinciples of Animal PhysiologyNervous System▪The Electromagnetic spectrumPrinciples of Animal PhysiologyNervous System▪Focusing of diverging light rays▸Cornea▸LensPrinciples of Animal PhysiologyNervous System▪Focusing on near and distant objectsPrinciples of Animal PhysiologyNervous System▪Accomodation - ability of lens to adjust strength to focus on both near and distant objectsPrinciples of Animal PhysiologyNervous System▪Retinal layersPrinciples of Animal PhysiologyNervous System▪PhotoreceptorsPrinciples of Animal PhysiologyNervous System▪Photopigments - undergo chemical alternations when activated by light▸Consists if opsin, an enzyme and retinene, from vitamin A▸Rhodopsin - vertebrate rod photopigment♦Provides vision in shades of gray▸Porphyropsin - insect rod pigment▸4 cone photopigments - red, green, blue, and ultraviolet♦Respond to selective wavelengths♦Makes color vision possiblePrinciples of Animal PhysiologyNervous System▪Phototransduction▸Virtually the same for all vertebrate photoreceptorsPrinciples of Animal PhysiologyNervous System▪The mammalian visual pathwayPrinciples of Animal PhysiologyNervous System▪Sound waves, ears and hearing▸Uses♦Early detection of