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The Senses

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The Senses. Chapter 35.4. Sensory Receptors. Sensory receptors react to specific stimuli Stimuli include light, sound, motion, chemicals, pressure, and changes in temperature. Sensory Receptors. - PowerPoint PPT Presentation

Text of The Senses

  • The SensesChapter 35.4

  • Sensory ReceptorsSensory receptors react to specific stimuli

    Stimuli include light, sound, motion, chemicals, pressure, and changes in temperature

  • Sensory ReceptorsEach sensory receptor reacts to a specific stimulus by sending impulses to other neurons, and eventually to the central nervous system (CNS)

    Most sensory receptors are found in sense organsex. eyes, inner ear, nose, mouth, and skin

  • Categories of Sensory ReceptorsThere are five major categories of sensory receptors:1. pain receptors2. thermoreceptors3. mechanoreceptors4. chemoreceptors 5. photoreceptors

  • Categories of Sensory ReceptorsPain receptorsFound all over the body EXCEPT in the brainRespond to chemicals released by damaged cells

    ThermoreceptorsLocated in the skin, body core, and hypothalamusDetect variations in temperature

    MechanoreceptorsFound in the skin, skeletal muscles, and inner ear Sensitive to touch, pressure, stretching of muscles, sound, and motion

  • Categories of Sensory ReceptorsChemoreceptorsLocated in the nose and taste budsSensitive to chemicals in the external environment

    PhotoreceptorsLocated in the eyesSensitive to light

  • VisionLight enters through the cornea (a tough transparent layer of cells)cornea helps focus light

    Light passes through a chamber filled with a liquid called aqueous humor

    At the back of the chamber is the irisiris is the colored part of eye

  • VisionIn the middle of the iris is the pupil (small opening) Regulates the amount of light that enters the eyeBehind the iris is the lens Changes shape to help adjust the eyes focus to see near or distant objectscontrolled by muscles

  • VisionBehind the lens is a chamber filled with vitreous humor (a transparent, jelly-like fluid)

    Light is focused on retinaPhotoreceptors found hereConverts light to nerve impulses which are then carried to the CNS

  • The RetinaTwo types of photoreceptors found on the retina:Rods very sensitive to light but not to colors

    Conesnot as sensitive to light but responds to light of different colors, producing color vision

  • RetinaCones are concentrated in the foveafovea = site of sharpest vision

    A blind spot is a spot on the retina where no photoreceptors existblind spot = where optic nerve passes through back of eye

  • Section 35-4Figure 35-14 The Eye

  • QuestionIf a tree falls in the woods and no one is there to hear, does it make a sound?

  • Section 35-4Figure 35-15 The Ear

  • HearingSound is vibrations in the airThe ear distinguishes the pitch and loudness of the vibrations

    Vibrations enter the ear through the auditory canalThese vibrations hit the tympanum (eardrum)

  • HearingThe vibrations picked up by the tympanum are transferred to three boneshammer, anvil, stirrupThese are the smallest bones in the body

    The stirrup transmits the vibrations to the oval window

    When the oval window vibrates, it creates pressure waves in the cochlea

  • CochleaThe cochlea is fluid-filled and lined with tiny hairsThe pressure waves produced by the oval window push the hairs back and forth

    This hair movement produces a nerve impulse that is transmitted through the cochlear nerve to the CNS

  • BalanceSemicircular canals, and two tiny sacs behind them, monitor the position of your body, especially your head, in relation to gravity

    Each canal and sac is filled with fluid and hairAs your head changes position, the fluid moves causing the hair to bendThe CNS receives a nerve impulse to determine body motion and position

  • Smell and TasteThe senses of smell and taste are a result of chemoreceptors sending nerve impulses in response to chemicals in the environment

    Smell ability of chemoreceptors lining the nasal passageway to respond to chemicals

    Taste ability of taste buds to detect chemicalsTaste buds are broken into categories: salty, bitter, sweet, and sourThe tongues sensitivity to each varies by region

  • TouchIt is a unique sense in that the nerves are not found in one particular region of the bodyall regions of skin are sensitive to touchIt responds to temperature, pressure, and pain

    Different body parts have different concentrations of nervesmore touch receptors found on fingers, toes, and face

  • Section 35-4The Senses of Smell and Taste