Gate Theory

Question 1

Gate Theory

Answer 1

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…

Question 2

Analgesia

Answer 2

pain reduction

Question 3

Nociceptors release

Answer 3

Substance P in Spinal cord, stimulating “T Cells” to send message up to brain, except when…

Question 4

Periaqueductal Grey Area

Inhibits?

Stimulates?

Answer 4

a (PAG in Midbrain) 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”)

Question 5

Touch Receptors

Answer 5

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

Question 6

Collateral that synapses in Spinal Cord stimulates…

Answer 6

inhibitory inter-neurons, prevent T Cells from reacting to Substance P

Question 7

Within brain,

Answer 7

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

• So, via Axo-Axonal connections, Endorphins directly inhibit Presynaptic release of Substance P in brain ‘
• e.g. On cue from Hypothalamus when sexual activity begins (anticipatory pain prevention)
• e.g. During strenuous exercise (producing “Runner’s high”)

Question 8

Acupuncture

Answer 8

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

Question 9

Naloxone

Answer 9

– an Endorphin Antagonist – blocks effects of Acupuncture