bio 10

  1. 3 types of somatosensation


  2. (types of somatosensation) Exteroceptive
    -perception of stimuli applied to the skin
  3. (types of somatosensation) Proprioceptive
    -perception of joints, muscles, and balance. Important for knowing where your body is in space
  4. (types of somatosensation) Interoceptive
    internal signals such as body temp and blood pressure
  5. 4 types of receptors in exteroceptive system
    • - free nerve endings
    • *temp, pain



  6. (types of receptors ext. sys.) Free nerve endings
    nerve endings on skin

    *pick up information on temp, pain, etc.
  7. (types of receptors ext. sys.) Pacinian (3)
    -respond to displacement of the skin (pressure)

    -rapidly adapting

    -best suited for sensing suddent change
  8. (types of receptors ext. sys.) Ruffini
    -adapt slowly

    -best suited to signal gradual changes in skin stretch
  9. (types of receptors ext. sys.) merkel
    -adapt slowly

    -best suited to singla gradual changes in skin indentation
  10. Image Upload 1
  11. processes from the exterocepticve receptors gather and roject to the...
    spinal cord where they enter via dorsal root ganglion.
  12. Dermatome
    area of skin that is served by the dorsal root ganglion
  13. topographyImage Upload 2
    -orderly entry of dermatomes into the spinal cord

    -topography is maintained all the way to the cortx just like in the viual and auditory systems
  14. From the skin to the brain steps
    1. info enters via dorsal root ganglion

    2. information projects to and synapses on to cells of dorsal column nuclei

    • 3. CONTRALATERAL projection to ventral posterior nucleus of the thalamus
    • 4. then arrives at primary somatosneory cortex
  15. Thalamus has stops for 4/5 follwing senses...



  16. (thalamus) Vision
    lateral geniculate nucleus

    -located in occipital
  17. (thalamus) audition
    medial geniculate nucleus

    -located in temporal
  18. (thalamus) Gustation
    ventral posterior medial nucleus

    -located in frontal
  19. (thalamus) Somatosensation
    ventral posterior nucleus

    -located in parietal
  20. where is the somatosensory located?
    -in the parietal lobe

    -posterior to the central sulcusImage Upload 3
  21. what is homunculus?
    somatosensory mapImage Upload 4
  22. The rceptive fieldsin homunculus vary...
    -representations vary per body part, some are more sensitive than others

    *receptive fields are much larger on our trunks than hands.
  23. PLasticity
    • brain structures can change to better cope with the environment
    • *constant stimulation can change the pattern of nuerons
  24. Phantom limb
    limb is lost, individual still feel sensations in that limb for days, months, and even years to come
  25. Cause of phantom limbs
    -representation of the limb in somatosensory cortex is still present

    Therefore, because the limb is no longer in use, adjacent areas of somasensory cortex might take over (plasticity)
  26. Damage to somatosensory cortex
    • -damahe to large portions or parietal cortex include primary and secondary leads to asomatognosia
    • *failure to recognize a body part as belonging to oenself

    • -can also result in contralateral neglect
    • *people fail to address their other side of body affected
  27. whats sensory feedback?
    • sensory systems interact with motor systems to guide appropriate motor behavior
    • *when we make a movement, all the following in used report back to evaluate how effective the movement was
  28. (sensorimotor association cortex) to make effective movements...
    • -we must know where our limbs are realtive to our body
    • *starting point

    -we must know location of the object we wish to target for grasping
  29. Posterior parietal association cortex
    -receives input from visual, auditory, and somatosensory systems

    -sends info to secondary motor cortex and other areas of association cortex involved in movement
  30. Secondary motor complex
    -receives information from sensorimotor association cortex

    -sends information to primary motor cortex

    -involved in planning of motor sequences

    *stimulation of secondary motor cortex evokes complex movements that involve both sides of the body
  31. Secondary motor complex continued...
    -neurons in this morter cortex begin responding before movement has been initiated

    • - some regions have bimodal responses.
    • *they respond to visual stimuli in addition to being involved in movements
  32. Primary motor cortex
    -individual areas of primary motor cortex control the movement of specific muscle groups

    • -it also receives 'feedback' from somatosensory system via somatosensory cortex as well as receptors in muscles and joints so that movements can be completed or modified
    • *throwing darts at bullseyes
  33. Location of primary motor cortex
    -located in the frontal lobe

    *just anterior to the central sulcusImage Upload 5
  34. pic of primary somatosensory
    Image Upload 6
  35. pic of primary motor complex
    Image Upload 7
  36. (descending motor pathways) dorsolateral pathways
    cross the middle line
  37. (descending motor pathways) ventromedial pathways
    does not cross the midline
  38. muscles are composed of many...
    individual muscle fibers
  39. 2 types of muscle fibers
    -slow twitch and fast twitch
  40. (types of muscles) Fast twitch
    contract faster but exhaust
  41. (types of muscles) Slow twitch
    contract more slowly but can contract more often
  42. (muscles and motor unit) a single motor nueron of the spinal cord innervates...
    a fixed number of muscle fibers
  43. (muscles and motor unit) motor nueron and the fibers it innervates is referred to as...
    motor unit
  44. (muscles and motor unit) when motor nueron fires an action potential...
    all the fibers it contacts will contract
  45. (muscles and motor unit) motor nueron realeases acetylcholine...
    which causes the muscle to contract
  46. what are the neural elements that talk to muscles and get them to contract?
    spinal motor nuerons
  47. none of the systems innervate muscles directly...
    they either directly or undirectly innervate neurons of the ventral horns of spinal cord
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bio 10