Histo Lecture 14

  1. How do sensory receptors transmit information?
    In a series of action potentials
  2. What is the Labeled Line Principle?
    Each type of sensation is projected to specific areas of the CNS
  3. The frequency of AP is dependent upon what?
    Intensity of the stimulus
  4. Define somatosensory receptors
    Specialized endings of primary afferent neurons
  5. What can somatosensory receptors be found?
    skin, viscera, muscles, joints, connective tissue
  6. Name some somatic sensations
    touch, pressure, vibration, body position, tickle, temperature, and pain (and itch)
  7. Recetors transform mechanical, chemical, and/or thermal energy into what?
    electrical energy (action potential)
  8. Name the 5 classifications of receptors
    • Mechanoreceptors
    • Thermoreceptors
    • Nociceptors
    • Chemorecptors
    • Electromagnetic receptors
  9. What are the two discriminatios of touch?
    • Quality of touch (soft or coarse)
    • Area being touched (2pt discrimination)
  10. What is Receptor Adaptation?
    Diminishing rate of discharge of a somatosensory neuron occurs with continued stimulation of constant intensity (adaptation)
  11. What is the purpose of adaptation?
    Allows the nervous system to focus on new or altered stimuli without the "distraction" of the constant stimulus
  12. What are rapidly adapting receptors called?
    Phasic receptors
  13. What are slowly adapting receptors called?
    Tonic receptors
  14. Describe Meissner's Corpuscle
    • Encapsulated, located in the ridges of superficial glaborous skin
    • Highly concentrated in the fingertips
    • Sensitive to: Light, touch, and discriminative touch
    • Rapidly adapting
  15. Describe Merkel's Disks
    • Un-encapsulated; Located in the superficial skin (hairy and glaborous)
    • Concentrated in the finger tips
    • Sensitive to discriminative touch
    • Slowly adapting
  16. Describe Pacinian Corpuscles
    • Encapsulated
    • located within: Dermis, subcutaneous fat, intramuscular connective tissue, and capsules of synovial joints
    • Detects pressure, vibration, and acceleration
    • Rapidly adapting
  17. Describe Ruffini's Endings
    • Encapsulated, flower-spray neural endings
    • Dermis, joints, glaborous, and hairy skin
    • Detects light touch
    • Slow adapting
  18. Describe the Hair Follicle
    • Nerve endings embedded in hair follicle, surrounding hair shaft
    • Deflection of hair deforms follicle, creating a stimulus for the receptor
    • Consist of rapidly and slowly adapting types
  19. What are two types of Thermoreceptors?
    • Krause's bulb - for cold
    • Ruffini's ending - for warm
  20. What are Nociceptors?
    Stimulatd by mechanical, termal, or chemical stimuli
  21. What are some chemical substances that stimulate nociceptors?
    Bradykinin, serotonin, histamine, K+ and H+
  22. Prostaglandins and substance P increase sensitivity to what?
    Pain (sensitize free nerve endings)
  23. What is hyperalgia?
    Increased sensitivity to painful stimuli
  24. What are Free Nerve Endings?
    Mechanical, Chemical, and Thermal stimuli
  25. Rate and extent of tissue damage is directly correlated with what?
    Level of pain perceived
  26. What are some causes of tissue damage?
    Bacterial infection, tissue ischemia, tissue contusion
  27. Describe fast pain
    • Elicited by mechanical and thermal stimuli
    • Transmitted on A-d (lower case greek delta) fibers
    • Sharp, easily localized pain
  28. What is a receptor potential?
    When a stimulus causes a change in the membrane electrical potential of a sensory receptor
  29. What does a receptor potential cause?
    A change in ion permeability of the receptor membrane and results in depolarization of receptor
  30. A stronger stimulus results in what?
    Increased action potential frequency
  31. A receptor will continue to send action potentials as long as...
    a stimulus is present (continued depolarization)
  32. What is adaptation?
    Diminishing rate of discharge of a somatosensory neuron that occurs with continued stimulation of constant intensity
  33. What does adaptation allow?
    Allows the nervous system to focus on new or altered stimuli without the distraction of the constant stimulus
  34. What are some influenctial factors of adaptation rates?
    • Properties of excitability of the membrane of the sensory neuron
    • The non-neuronal accessory structure that surrounds the axon
  35. What is referred pain?
    Pain felt in part of the body that is remote from the tissue causing the pain
  36. When does referred pain most frequently occur?
    With injury to visceral organs (abdomen/thorax)
  37. Where do visceral and skin pain fibers terminate? Why is this important?
    • Terminate at the same areas of spinal cord;
    • The CNS perceives the pain as coming from the skin rather than abdominal/thoracic organs
  38. What is the modality and adaptation rate of Meissner's?
    • Discriminate touch, light touch, vibration
    • Rapidly adapting
  39. What is the modality and adaptation rate of Merkel's?
    • Discriminate touch
    • Slowly adapting
  40. What is the modality and adaptation rate of Pacinian?
    • Pressure, vibration, acceleration
    • Rapidly adapting
  41. What is the modality and adaptation rate of Ruffini's?
    • Light touch, thermoreceptor
    • slowly adapting
  42. What is the modality and adaptation rate of hair end organs?
    • Light touch
    • Rapid & slowly adapting
  43. What is the modality and adaptation rate of free nerve endings?
    • Chemical, thermal, mechanical
    • Slow or no adapting
Card Set
Histo Lecture 14
Sensory Receptors