Transcript PowerPoint
Senses Senses Perceive environment Find food Avoid predators Avoid danger Find shelter Interact socially Sensory Receptors Mechanoreceptors Touch, hearing, equilibrium, pressure Thermoreceptors Radiant energy, infrared Nociceptors Pain Chemoreceptors Smell, taste Osmoreceptors Water, solute concentration Photoreceptors Light, vision Sensory Receptors Sensory receptor Nerve pathway Brain integration Sensory perception Sensory Receptors Receptors specific for given stimulus Strong stimulation Greater frequency of action potentials Greater number of neurons Sensory adaptaion Frequency of AP decrease or stop w/ constant simulus Somatic Start at sensory neurons Different sensors to different part of brain Somatosensory cortex Somatic Body surface Free nerve endings Meissner corpuscles Pacinian corpuscles Thermoreceptors Bulb of Krause Ruffini endings Somatic Muscles Mechanorecptors Motion Position in space Stretch Somatic Pain—perception of injury Nociceptors Somatic—skin, skeletal muscle, joints, tendons Visceral—internal organs Fewer nocieptors “Referred” pain Cell damage releases bradykinins Bradykinins stimulate nearby nociceptors Stimulus perceived by brain as pain Olfaction Smell Social communication Find mates Find prey Avoid predators Olfaction Well-developed in most mammals Especially carnivores & ungulates Non-existent in cetaceans (whales, dolphins, etc.) Canines 100,000-1 million times better than humans Bloodhounds 10-100 million times Olfaction Poorly developed in most birds Well-developed in fish Salmon—ID and return to home streams Catfish—ID others, maintain social order Olfaction Chemicals inhaled Must be dissolved in liquid (mucus) Binds to membrane proteins Triggers depolarization of neurons Different combinations of receptor activation recognized as patterns by brain Olfaction Olfaction Pheromones Air-borne chemical that triggers behavioral response in same species Alarm Food trail Sex Territorial Taste Differentiate nutrition vs. noxious Receptors on various organs Antennae Tentacles Tongue Legs Taste Five tastes in humans Sweet Sour Salty Bitter Umami Chemoreceptors Antennae Most arthropods Multiple functions Smell & taste most important Also touch, air motion, vibration, heat Olfactory receptors bind to odor molecules Sends signal to antennal lobe in brain Chemoreceptors Vomeronasal organ Many animals (including humans) Certain smells Many pheromones May be involved in triggering some aggression & mating Chemoreceptors Vomeronasal organ Flehmen response In cat In deer Hearing Detect vibrations Interpret as sound Amplitude (loudness) Frequency (pitch) Important for communication Important for finding prey Important for avoiding predators Hearing Sonic—human frequencies 15 Hz-20,000 Hz Best at 2,000-4,000 Hz Ultrasonic—above human frequencies Bats, dogs Subsonic—below human frequencies Snakes (sense through bellies) Whales, giraffes, elephants (communication) Hearing External ear (pinna) Collects sound Middle ear Ossicles Malleus (hammer) Incus (anvil) Stapes (stirrup) Receive vibrations from tympanum (eardrum) Transmit to inner ear Inner ear Cochlea—auditory nerves Semicircular canals—balance Hearing ,,, Hearing Vibrations coming down ear vibrate ossicles Stapes vibration pushes on oval membrane on cochlea Fluid in cochlea moves at specific frequency Fluid wave moves tectorial membrane Movement of tectorial membrane stimulates nerve impulse Hearing ,,, Hearing Equilibrium Vestibular organs (semicircular canals) Static equilibrium Linear movement of head Otolithic membrane movement triggers hairs Dynamic equilibrium Rotation, acceleration, deceleration Fluid bends hairs in crista ampullaris Hearing Echolocation Dolphis, shrews, bats, most whales Active sonar Sounds sent out Hear reflection of sounds (echo) Able to triangulate sounds “Hearing” Lateral line Detect vibrations in water Along sides of many fish Similar to certain aspects of hearing & equilibrium Vision Photoreceptors Part of brain that can interpret pattern of nerve impulses Pigment molecules absorb incoming photons Convert photons into action potential Vision Invertebrate Simple Photosensitive receptors Do not form images Light & dark Ocellus Vision Invertebrate Compound Arthropods Multiple facets Each has own lens & photoreceptor cells Very sensitive to motion 360o field of vision Multiple images integrated in brain Poor image resolution Vision Invertebrate Mollusks Many have lens eyes (similar to vertebrates) Cephalopods have most developed Hunters, 3 dimensions, often move fast Vision Vertebrate Outer layer Sclera Cornea Middle Layer Lens Iris Pupil Choroid Aqueous Humor Vitreous Humor Vision Inner layer Retina Macula lutea Optic disc Tapetum Lucidum Vision Rods Low light Night vision No color Cones Bright light Day vision Color Vision Accommodation—the process by which an eye changes to keep an object in focus as it moves closer or further away. Fish, reptiles—Lens moves forwards & backwards in eye Birds, mammals—ciliary muscles change shape of lens. Vision Photons enter through cornea Are focused by lens Absorbed by cells in retina Photon activity stimulates receptors to generate action potential Vision Eye placement Forward-facing Predators Depth perception Side-facing Prey Wide field of vision Other Senses Electroception Detect electrical fields Sharks, skates, rays Lungfish, coelacanths, sturgeons Monotremes (especially platypus) Active—generate own field Electric eels & fish Communication Passive—sense other fields Chondrichthyes Other Senses Magnetoception Mostly birds Very important to migration Some bees Detect magnetic fields Magnetite Found in many rocks & minerals Source of iron ore Identified in brains of birds, bees, and humans When magnetite aligns w/ Earth’s magnetic field, stimulates nerve impulse Poorly understood sense