Pain Gate theory : Centers in CNS , Mechanism , Nerve fibers Involved

2. PAIN GATE THEORY
• Ghalib hussain Khan
• bs. PhysiotheraPy
• institute of
PhysiotheraPy
luMhs JaMshoro
sindh
eMail:dr.Khan127@GMail.
coM

4. • Gate control theory was described by Melzack and
Wall in 1965.
• This theory explains about a pain-modulating
system in which a neural gate present in the spinal
cord can open and close thereby modulating the
perception of pain.
• The gate control theory suggests that psychological
factors play a role in the perception of pain.

5. • It also suggests that physical pain is not a
direct result of activation of pain receptor
neurons, but rather its perception is
modulated by interaction between different
neurons.

6. Centers in CNS
• · The three systems located in the spinal
cord act to influence perception of pain
• The substantia gelatinosa in the dorsal
horn,
• The dorsal column fibers
• The central transmission cells.

7. • The dorsal horn is responsible for passing
on information which can be interpreted as
pain. This area is referred to as the 'gate'
as it prevents the brain from receiving too
much information too quickly.
DORSAL HORN of
spinal cord grey
matter

8. Neurons involved in pain conduction
• 1. Primary: from the ‘nociceptors’)
to the dorsal horn of the spinal cord.
• 2. Secondary: from the dorsal horn
to the thalamus.
• 3. Tertiary: from thalamus to cortex
and awareness.
Tertiary
Neuron
Secondary
Neuron
Primary
Neuron
Nocicept
ors

9. Mechanism:
Trauma Receptors A-delta
C fibers
Afferent Pathway
Thalamus
Reticular Formation
PAG
Cortex
Higher centers
“ouch”
“mommy”

10. Nerve fibers Involved
• The smaller, unmyelenated A (delta) and C nerve
fibers sense pain such as sharp burning and
aching feelings.
• Larger, myelenated A (beta) skin nerves which
carry senses of touch, heat, cold and pressure.
• The A (beta) nerves are faster, and also have
priority which effectively blocks out the pain
messages to the brain and closes the gate.

11. • Stimulation of the large-diameter fibers (A-Fibers)
inhibits the transmission of pain (“closing the gate)
• Stimulation of the Small-diameter fibers (C-Fibers)
stimulates the transmission of pain (opening the Gate)
• When the gate is closed, signals from small diameter
pain fibers do not excite the dorsal horn transmission
neurons.
• · When the gate is open pain signals excite dorsal horn
transmission cells.
• · The gating mechanism is influenced by nerve impulses
that descend from the brain

12. • Factors which influence opening and
closing the gate are:
• The amount of activity in the pain fibers.
• The amount of activity in other
peripheral fibers
• Messages that descend from the brain.

13. • Gate may be closed by:
• Physical Pain - Analgesic Remedies
• Emotional Pain - Being in a ‘good’ mood
• Behavioral Factors - Concentrating on things
other than the injury
• Relaxation and Contentment –
• Mental factors: - work, T.V., book,
• Activity - Taking exercise,
• counter-stimulation- heat, massage,
acupuncture

14. • Gate is opened by
• Physical Factors - Bodily injury
• Emotional Factors - Anxiety &
Depression
• Behavioral Factors - Attending to the
injury and concentrating on the pain
• Lack of Activity –
• Mental Factors –

15. ?? Questions ??