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Chapter 15

Chapter 15. Neural Integration I: Sensory Pathways and the Somatic Nervous System. fig. 15-1. Sensory. Motor. General (15). Somatic (15). Special (17). Autonomic (16). Special senses. smell sight taste hearing. special “sense” organs. General senses. temperature pain touch

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Chapter 15

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  1. Chapter 15 Neural Integration I: Sensory Pathways and the Somatic Nervous System

  2. fig. 15-1

  3. Sensory Motor General (15) Somatic (15) Special (17) Autonomic (16)

  4. Special senses smell sight taste hearing special “sense” organs General senses temperature pain touch pressure vibration proprioception most associated with the skin

  5. General senses receptors distributed throughout the body relatively simple

  6. General senses • receptors send info to CNS • arriving info is calledsensation • our awareness of it isperception

  7. Sensory receptors interface between environment and the body translate stimulus into an AP transduction

  8. Sensory receptors receptors have selective sensivity chemical physical touch light heat transfer receptors may or may not have accessory structures associated with them

  9. Sensory receptors receptive field area monitored by a receptor size of receptive field 70 mm 1 mm specificity fig. 15-2

  10. Sensory receptors stimulus receptor • stimulus changes • membrane potential • receptor potential (+ or -) greater stimulus means larger receptor potential if stimulus is large enough to get to threshold is is called generator potential ( generates an AP) transduction

  11. Sensory receptors stimulus receptor action potential CNS for processing and interpretation (cortical areas)

  12. receptor B receptor 2 receptor A labeled line cortex

  13. a “line” carries the same “type” (modality) of information interpretation is based on which “line” information travels on

  14. receptor B receptor 2 receptor A labeled line optic nerve cortex shut eyes and rub them gently

  15. When CNS receives info… which “line” type of stimulus where “line” ends perception all other attributes (strength, duration, variation) are determined by the frequency and pattern of AP’s

  16. receptor types: tonic: always “on” phasic: only on with stimulus some receptors combine the two greater stimulus higher freq. lesser stimulus lower freq.

  17. adaptation reduction in sensitivity in the presence of a constant stimulus peripheral central change in receptor activity inhibition of nuclei in pathway

  18. peripheral adaptation phasic receptors (aka fast-adapting receptors) example: thermoreceptors you usually don’t notice room temperature unless it changes

  19. central adaptation example: smell you walk into a room and notice a new smell… …but not for long

  20. adaptation reduces the amount of information reaching the cerebral cortex about 1% of sensory information coming in reaches our awareness

  21. 100 Keys (pg 498) “Stimulation of a receptor produces action potentials along the axon of a sensory neuron. The frequency or pattern of action potentials contains information about the strength, duration, and variation of the stimulus. Your perception of the nature of that stimulus depends on the path it takes inside the CNS.”

  22. General senses (from chapter 12) exteroceptors proprioceptors interoceptors outside position inside

  23. General senses • classification • based on nature of stimulus pain heat flow physical distortion chemical concentration nociceptors thermoreceptors mechanoreceptors chemoreceptors

  24. General senses nociceptors • common in: • skin • joint capsules • coverings of bones • around blood vessel walls free nerve endings large receptive fields

  25. nociceptors • sensitive to: • extreme temperature • mechanical damage • dissolved chemicals • (like those release by damaged cells) stimulation causes depolarization

  26. nociceptors • two fiber types convey info • type A • fast pain (cut, etc.,) • easy to localize • type C • slow pain (“burning, aching”) • difficult to localize

  27. nociceptors tonic receptors no significant peripheral adaptation as long as the stimulus is present, it will hurt but central adaptation can occur (perception of pain may decrease)

  28. nociceptors sensory neurons bringing in pain info use glutamate and/or substance P as their neurotransmitter these nts can cause facilitation (?) pain may be disproportional (feels worse than it should) pain can be reduced by endorphins and enkephalins (inhibit activity in pathway) [neuromodulators chpt. 12]

  29. nociceptors endorphins pain centers use substance P as nt. endorphins bind to presynaptic membrane and inhibit substance P release, reducing perception of pain

  30. to here 3/9 lec # 24

  31. thermoreceptors free nerve endings in the dermis skeletal m. hypothalamus liver warm receptors or cold receptors

  32. thermoreceptors • phasic receptors • active when temperature is changing, quickly adapting to stable temperature • detect transfer of heat • heat loss from skin cool • heat gain to skin warm

  33. mechanoreceptors contain mechanically regulated ion channels (chapter 12)

  34. c. mechanically regulated channels closed mechanical stimulus- opens remove stimulus- closed fig. 12-10c

  35. mechanoreceptors three classes tactile receptors baroreceptors proprioceptors touch, pressure, vibration pressure changes (gut, genitourinary) position of joints/muscles

  36. mechanoreceptors tactile receptors fine touch/pressure crude touch/pressure small (narrow) receptive field detailed information sensitive wide receptive field poor localization

  37. fig. 15-3

  38. tactile receptors range of complexity free nerve endings root hair plexus tactile discs tactile corpuscles (Meissner’s) lamellated corpuscles (pacinian) Ruffini corpuscles

  39. tactile receptors free nerve endings in epidermis of skin cornea of eye sensitive to touch and pressure tonic receptors small receptive field

  40. tactile receptors root hair plexus around each hair follicle sense movement of hair adapt quickly

  41. tactile receptors tactile discs • sensitive, tonic receptors • in epidermis • fine touch and pressure

  42. tactile receptors tactile corpuscles (Meissner’s) fine touch, pressure , vibration adapt quickly surrounded by Schwann cells in dermis of skin eyelids, fingertips (sensitive areas)

  43. tactile receptors lamellated corpuscles (pacinian) • sensitive to deep pressure • high-frequency vibrations • adapt quickly • nerve ending is encapsulated • by layers of supporting cells • (onion) • dermis, pancreas, fingers…

  44. tactile receptors Ruffini corpuscles pressure and skin distortion located deep in the dermis tonic, little if any adaptation

  45. fig. 15-3

  46. sensivitity can be altered infection disease damage to pathway e.g., damage to a spinal nerve would affect an entire dermatome

  47. tickle and itch closely related to touch and pain

  48. baroreceptors • free nerve endings in the walls of organs that stretch • e.g., blood vessels when pressure changes they expand or contract changes activity of receptors

  49. proprioceptors muscle spindles Golgi tendon organs receptors in joint capsules stretch reflex monitor tendon tension free nerve endings in joints

  50. proprioceptors no adaptation continuously send info to CNS most processed at subconscious level

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