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Chapter 10

Chapter 10. Sensory Physiology. About this Chapter. What are the senses How sensory systems work Body sensors and homeostatic maintenance Sensing the external environment Mechanisms and pathways to perception. General Properties of Sensory Systems. Stimulus Internal External

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Chapter 10

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  1. Chapter 10 Sensory Physiology

  2. About this Chapter • What are the senses • How sensory systems work • Body sensors and homeostatic maintenance • Sensing the external environment • Mechanisms and pathways to perception

  3. General Properties of Sensory Systems • Stimulus • Internal • External • Energy source • Receptors • Sense organs • Transducer • Afferent pathway • CNS integration

  4. The Human Brain

  5. General Properties of Sensory Systems Figure 10-4: Sensory pathways

  6. Sensory Receptor Types • Simple receptors • Complex neural • Special senses • Chemoreceptors • Mechanoreceptors • Thermoreceptors • Photoreceptors

  7. Sensory Receptor Types Figure 10-1: Sensory receptors

  8. The Cerebral Cortex • Three kinds of functional areas • Motor areas • Sensory areas • Association areas

  9. Association Areas • Association cortex : Essential for mental functions that are more complex than detecting basic dimensions of sensory stimulation, for which primary sensory areas appear to be necessary. In humans the association areas are by far the most developed part of the cerebral cortex, and the brain in general. These areas are necessary for perceptual activities, like recognizing objects (toasters, horses, trees, words, etc), rather than simple contours, edges or sensory qualities like color or pitch. • Each sensory system has its own association areas on the cerebral cortex. The sensory systems (vision, hearing, etc.) each have their own primary area on the cortex, which gets the most direct connections from its sense. Each primary sensory area sends information to its own cortical association areas, which are next to their primary areas

  10. Functional and Structural Areas of the Cerebral Cortex

  11. Functional and Structural Areas of the Cerebral Cortex Figure 13.11b

  12. Special Senses – External Stimuli • Vision • Hearing • Taste • Smell • Equilibrium

  13. Special Senses – External Stimuli Figure 10-4: Sensory pathways

  14. Sensory Areas – Sensory Homunculus Figure 13.10

  15. Motor Homunculus Figure 13.10

  16. Homunculus

  17. Somatic Senses – Internal Stimuli • Touch • Temperature • Pain • Itch • Proprioception • Pathway Figure 10-10: The somatosensory cortex

  18. Somatic Pathways • Receptor • Threshold • Action potential • Sensory neurons • Primary – medulla • Secondary – thalamus • Tertiary – cortex • Integration • Receptive field • Multiple levels

  19. Somatic Pathways Figure 10-9: Sensory pathways cross the body’s midline

  20. Sensory Modality • Location • Lateral inhibition • Receptive field • Intensity • Duration • Tonic receptors • Phasic receptors • Adaptation

  21. Touch (pressure) • Mechanoreceptors • Free nerve endings • Pacinian corpuscles • Ruffini corpuscles • Merkel receptors • Meissner's corpuscles • Baroreceptors

  22. Touch (pressure) Figure 10-11: Touch-pressure receptors

  23. Temperature • Free nerve endings • Cold receptors • Warm receptors • Pain receptors • Sensory coding: • Intensity • Duration

  24. Temperature Figure 10-7: Sensory coding for stimulus intensity and duration

  25. Pain and Itching • Nocioceptors • Reflexive path • Itch • Fast pain • Slow pain

  26. Pathways of Itch from Skin to Brain. Yosipovitch G, Bernhard JD. N Engl J Med 2013;368:1625-1634.

  27. Gate Control Theory of Pain Figure 10-12: The gate control theory of pain modulation

  28. Pain • Ischemia • Other visceral pain • Modulation • Thalamus • Gate control • Magnification • Analgesic drugs • Aspirin • Opiates

  29. Referred Pain Figure 10-13: Referred pain

  30. Olfactor: Sense of Smell • Olfactory cell • Chemoreceptor- Humans have about 350 different types of odorant receptors, Mice 1200 • Olfactory cilia • Olfactory bulb • Olfactory nerve • CNS integration • Amygdala • Hippocampus • Olfactory

  31. Olfactor: Sense of Smell Figure 10-14a, b: ANATOMY SUMMARY: Olfaction

  32. Olfactor: Sense of Smell Figure 10-14c: ANATOMY SUMMARY: Olfaction

  33. Taste: Chemoreceptors • 5 Tastes • Taste buds • Taste cells • Mechanism • Transduction • Integration • Thalamus • Gustatory cortex • "Specific hunger" Figure 10-16: Summary of taste transduction

  34. Hearing: Mechanoreceptors • Sound waves • Conduction • Air • Bone • Fluid • Membranes • To hair cell

  35. Hearing: Mechanoreceptors Figure 10-19: Sound transmission through the ear

  36. Hearing: Hair Cell Transduction • Fluid wave moves • Tectoral membrane • Steriocilia move • Ion channels open • Depolarization • NT release • Sensory nerve AP

  37. Hearing: Hair Cell Transduction Figure 10-20: The cochlea

  38. Hearing: Hair Cell Transduction Figure 10-21: Signal transduction in hair cells

  39. Hearing: Integration and Problems • Pitch • Intensity • Localization • Integration • Medulla • Thalamus • Auditory cortex • Deafness • Conductive • Sensorineural Figure 10-5: Localization of sound

  40. Hearing: Integration and Problems Figure 10-22: Sensory coding for pitch

  41. Equilibrium: Mechanoreceptor • Body balance • Body position • Body movement • Propioceptors • Vision • Vestibular apparatus

  42. Equilibrium: Mechanoreceptor • Integration • Medulla • Cerebellum • Thalamus • Cortex Figure 10-26: Central nervous system pathways for equilibrium

  43. Equilibrium: Vestibular Apparatus • Otolith organs • Gravity • Calcite crystals • Hair cells • Semicircular canals • Endolymph Fluid moves which stimulates Each Crista which consists of: Cupula Embedded Hair cells: activate CN VIII

  44. Semicircular Canals of the Vestibular Apparatus • Have Posterior, Horizontal and Superior Semicircular Canals • They sense Rotational Acceleration in various directions • The Cristae within the Ampula (enlarged chamber at the end of each canal) are the sensory receptors • Endolymph moves the gelatinous cupula with the hair cells embedded in it and stimulates vestibulocochlear nerve (CN VIII)

  45. Equilibrium: Vestibular Apparatus Figure 10-23a, b: ANATOMY SUMMARY: Vestibular Apparatus

  46. Otolith Organs of the Vestibular Apparatus • Otolith Organs of the Utricle and Saccule Sense Linear Acceleration and Head Position • They are arranged horizontally (Utricle-if head tips back gravity causes othliths to slide) and vertically (Saccule-senses vertical forces such as an elevator dropping) • Macula are the sensory receptors of the utricle and saccule • Otoliths are crystals that move in response to gravitational forces

  47. Equilibrium: Vestibular Apparatus Figure 10-23c, d: ANATOMY SUMMARY: Vestibular Apparatus

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