Somatosensory System

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Somatosensory System
2013-10-21 22:11:02
Somatosensory SLP neuro

Brief description of somatosensory system
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  1. What do sensations of the body do? What is this system called?
    What are the special senses?
    • distinguish different types of stimuli, somatosensory system 
    • Audition, vision, gustatory, balance
  2. Difference between special senses and somatosensory system (2):
    • 1. Somatosensory receptors are distributed throughout the body, special sensory receptors are localized
    • 2. Somatosensory system consists of 4 senses, special sensory receptors consist of just 1
  3. What are the 4 somatosensory senses?
    • 1. touch (mechanoreceptors)
    • 2. temperature (thermoreceptors)
    • 3. Pain (nocireceptors)
    • 4. Body Position (stretch receptors)
  4. What type of sensory information does a unipolar neuron carry? What about bipolar neuron?
    • 1. skin and organs 
    • 2. special senses
  5. Mechanoreceptors respond to (3):
    • 1. Bending
    • 2. Stretching or
    • 3. Squishing 

    This is a touch* receptor
  6. The structure of the end of a __________ _____ will determine the neuron's responsivity to stimulus (deep pressure, light pressure, stretching, bending, etc). This is termed as ________. Once the membrane is compressed and the axon has selected for the stimulus (3):
    • Mechanoreceptive axon
    • selectivity
    • 1. Ion channels open
    • 2. Depolarization of receptor potential 
    • 3. Action Potential
  7. ______ ______ ___ bring information from receptors to the SC or the brainstem. 
    There are 4 types of axons that carry different information:
    • Primary afferent axons 
    • 1. Proprioceptors of skeletal muscles (thickest myelin) 80-120 m/sec
    • 2. Mechanoreceptors of skin 35-75 m/sec
    • 3. Pain, temperature 5-30 m/sec
    • 4. Temperature, pain, itch (thinnest myelin) .5-2 m/sec
  8. Where does sensory information from in the head enter CNS?
    Where does sensory information from below the head enter CNS?
    What is a dermatome?
    • Cranial nerves
    • Spinal nerves
    • Skin area connected to a single sensory spinal nerve
  9. Discuss the path from the sensory receptor to the CNS:
    • 1. Afferent axons enter dorsal horn, branch and go to: the brain or: second-order neurons in dorsal horn where the ventral horn will then mediate reflexes.
    • 2. Fasciculus Gracilis carries lower body sensation info, Fasciculus Cuneatus carries upper body sensation info: course upwards: decussate at medial lemniscus in the medulla: goes through thalamus: ends at primary somatosensory cortex. Sensory info form the face is carried by the trigeminal nerve: decussates at the cerebellum: goes through the thalamus: ends at primary somatosensory cortex.
  10. What is the purpose of the homonculus?
    The Primary Somatosensory Cortex and the Posterior parietal cortex?
    • The size of cortex devoted to an area depends on the density and importance of sensory input (articulators, face, hands)
    • PSC gathers sensory info then sends it to PPC
  11. The Posterior Parietal Cortex:
    Damage of this can result in:
    • Simple sensory info converge here to generate complex neural representations. 
    • Agnosia (tactile agnosia), neglect syndrome
  12. What is the difference between nociception and pain?
    What is a nociceptor?
    What is an interesting fact?
    • Nociception is the process that provides the signals that trigger pain. Pain is a feeling or perception of negative sensations. 
    • Free nerve endings that signal that body tissue is being damaged. 
    • The brain does not have nociceptors, but the meninges/blood vessels do (why we feel headaches)
  13. What pathway carries pain/temperature from the body to the brain?
    What pathway carries pain/temperature from the face and head to the brain?
    What might suppress feelings of pain?
    What suppresses nociceptive neuron activity?
    • Spinothalamic (anterolateral system)
    • Trigeminal pain pathway 
    • Emotion, stress, determination 
    • Periaqueductal gray matter (influence raphe nuclei)
  14. What do thermoreceptors do (2)?
    • In the hypothalamus and SC thermoreceptors regulate body temperature 
    • In the skin, thermoreceptors sense temperature in our environment
  15. Thermoreceptors are either sense (2):
    • warm or cold (not both)
    • warm: 86-113 F
    • cold: 50-95 F
    • When a stimulus is too hot, nocireceptors will fire, but if a stimulus is too cold, it acts as an anesthetic. 
    • Temperature and pain pathways are the same