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The Senses

The Senses. Somatic senses throughout body, including internal organs Touch, vibrations Temperature Pressure Pain Body position, movements Special senses - located in certain areas only Smell Taste Sight Hearing Balance. Sensory Receptors: Receive and Convert Stimuli.

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The Senses

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  1. The Senses • Somatic senses throughout body, including internal organs • Touch, vibrations • Temperature • Pressure • Pain • Body position, movements • Special senses - located in certain areas only • Smell • Taste • Sight • Hearing • Balance

  2. Sensory Receptors: Receive and Convert Stimuli • Mechanoreceptors: mechanical energy • Thermoreceptors: hot or cold • Pain Receptors: tissue injury, excessive pressure • Chemoreceptors: chemicals; taste and smell • Photoreceptors: light

  3. Receptor Adaptation to Continuing Stimuli • Purpose: CNS concentrates on important stimuli and ignores others • Receptors that adapt: light touch, pressure, smell • Receptors that do not adapt: pain, joint, and muscle monitoring receptors

  4. Sensory Receptors in Skin Figure 12.1

  5. CNS Interpretation • Location: nerves hard wired to specific portions of brain, specific nerve stimulus results in assigning specific location • Referred pain • Strength of feeling: frequency of nerve stimulus

  6. The Ear • Houses two senses in different organs • Hearing • Balance • Receptors are mechanoreceptors

  7. Anatomy of the Ear • The ear is divided into three areas • Outer ear • Pinna, auditory canal Figure 8.12

  8. The Middle Ear • Air-filled cavity within the temporal bone • tympanic membrane • Three bones span the cavity • Malleus (hammer) • Incus (anvil) • Stapes (stirrup) auditory tube

  9. Inner Ear or Bony Labyrinth • converts sound vibrations to nerve impulses • balance • Filled with perilymph • Chambers: • Cochlea • Vestibule • Semicircular canals Figure 8.12

  10. Mechanisms of Hearing Cochlea has 2 compartments: 1. Vestibular and tympanic canals (joined at far end) 2. Cochlear duct Figure 8.16a–b

  11. Organs of Hearing Cochlea in transverse section Organ of Corti Figure 8.15

  12. Mechanisms of Hearing 1. Sound waves 2. Tectorial membrane 3. Hair cells bend 4. Triggers action potential 5. Adaptation to stimulus Figure 8.16a–b

  13. Organs of Equilibrium • Receptor cells are in two structures • Vestibule - static equilibrium • Semicircular canals - dynamic equilibrium Figure 8.14a–b

  14. Sensing rotational movement Ampulla with mechanoreceptors in cupula Tuft of hair cells • Cupula (gelatinous cap) covers the hair cells Figure 8.14c

  15. Sensing head position and acceleration: vestibule with otoliths - reports on the position of the head Figure 8.13a–b

  16. Balance: Inner Ear • Specialized structures: • Vestibular apparatus: three semicircular canals and vestibule • Sensing rotational movement: ampulla with mechanoreceptors in cupula • Sensing head rotation and acceleration: in vestibule with otoliths

  17. Chemical Senses – Taste and Smell • Both senses use chemoreceptors • Stimulated by chemicals in solution • Taste has four types of receptors • Smell can differentiate a large range of chemicals - 1000+ • Both senses complement each other and respond to many of the same stimuli

  18. Olfaction – The Sense of Smell • Olfactory receptor cells: chemoreceptors that bind with odorants • Correlation between taste and smell: chewed food releases chemicals that come in contact with olfactory receptors

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