Somatosensory Cortex Flashcards

1
Q

Post Central Gyrus

A

of Parietal Lobe, just posterior to Central Sulcus that separates Parietal/ Frontal Lobes

Penfield Map

  • Multiple parallel maps for touch, proprioception, temperature, and pain
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2
Q

Penfield Map

A

Topological maps of body surface: Feet, legs, body, arms, hands, face

(“homunculus”,“little man”)

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3
Q

Magnification Facter

A

Any area with small Receptive Field and a high density of high acuity (1:1) receptors takes up a disproportionately large area of the cortical map (i.e. that body area is magnified in cortex – like Fovea of retina)

  • Thus bizarre Penfield Map has large hands (object ID, manipulate, gesture) & mouth (speak, eat, kiss) vs. small torso
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4
Q

Gate Theory

nociceptors release….

A

of endogenous Analgesia (pain reduction) via negative feedback from brain or body

  • Nociceptors release Substance P in Spinal cord, stimulating “T Cells” to send message up to brain, except when…
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5
Q

Periaqueductal Gret Area (PAG in Midbrain)

inhibits?

stimulate?

A

releases inhibitory Endorphins (“endogenous morphine”)

=> Inhibits Inhibitory cells in Raphe System in hindbrain, allowing Raphe to send Excitatory NT to Spinal Cord

=> Stimulate inhibitory inter-neurons in Grey Matter of Cord, prevent T Cells from reacting to Substance P (“Close Gate”)

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6
Q

Touch Receptors

A

near source of pain are stimulated (e.g. scratch around mosquito bite!)
- Collateral that synapses in Spinal Cord stimulates inhibitory inter-neurons, prevent T Cells from reacting to Substance P

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7
Q

Within brain

A

some cells that release Substance P have NT receptor sites on their Terminals that respond to inhibiting Endorphins

  • e.g. On cue from Hypothalamus when sexual activity begins (anticipatory pain prevention)
  • e.g. During strenuous exercise (producing “Runner’s high”)
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8
Q
  • So, via Axo-Axonal connections,
A

Endorphins directly inhibit Presynaptic release of Substance P in brain

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9
Q

Acupuncture

Naloxone?

A

may work by stimulating PAG Endorphin release, by directly stimulating inhibitory inter-neurons in cord, or both

  • Naloxone – an Endorphin Antagonist – blocks effects of Acupuncture
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