In physiotherapy pain gate pathway and pain control theory is important for the explanation behind the physiologic pain control.

1. PAIN GATE MECHANISM
DR. REKHA MARBATE
[ASSISTANT PROFESSOR]

3. INTRODUCTION
 Analgesic effect of interferential therapy – explained by inhibition type-C
nociceptive fibers.
 Pain gate theory- developed by Melzack and Wall

4.  the maximum frequency of transmission in C nerve fibers is 15 Hz and in Aδ
fibers is 40 Hz.
 The application of frequencies higher than this could block transmission
along these fibers altogether

5.  Short duration pulses at a frequency of 100 Hz may stimulate large diameter
nerve fibers which will have an effect on the pain gate in the posterior horn,
and inhibit transmission of small diameter noci-ceptive traffic.

6.  In order to selectively activate the descending pain suppression system, a
frequency of 15 Hz is required.
 The stimulation of small diameter fibers produced will eventually cause the
release of endogenous opiates (enkephalin and β endorphin) at a spinal
level.

7. PAIN PATHWAY
 afferent fibers are of two types
 A Delta fibers: Fast conducting large diameter myelinated fibers, which
conducts with a velocity of 5–30 m/s.
 C-fibers: Slow conducting small diameter nonmyelinated fibers, which
conducts with a velocity of 2–5 m/s.

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
or
s

10. CONTINUED..
 primary afferent fibers transmit impulses from the sensory receptors to the
dorsal horn of the spinal cord.
 Second order afferent fiber carry sensory impulses from the dorsal horn of
the spinal cord to the brain.
 First order neurons include A-alpha, A-beta, A-delta and C-fibers.
 A-alpha and A-beta fibers are characterized by having large diameter
afferents and
 A-delta and C-fibers are characterized by having small diameter afferents.
 The second order afferents are nociceptive specific

11.  A nociceptive neuron transmits pain signals.
 Its cell body lies in the dorsal root ganglion.
 A-delta and C-fibers transmits the sensation of pain.
 Fast pain is transmitted over the larger, faster-conducting A-delta afferent
neurons and originates from receptors located in the skin.
 Slow pain is transmitted by the C afferent neurons and originates from both
superficial (skin) and deeper (ligaments and muscle) tissue.

12.  Most nociceptive second-order neurons ascend to higher centers along one
of three tracts:
 (1) Lateral spinothalamic tract,
 (2) Spinoreticular tract, and
 (3) Spinoencephalic tract,
 with the remainder ascending along the spinocervical tract or as projections
to the cuneate and gracile nuclei of the medulla.
 Approximately 90% of the wide dynamic range second-order afferents
terminate in the thalamus.

13. MECHANISM OF PAIN GATE CONTROL

14. 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.

15. 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

16. 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 –

17. ?? QUESTIONS
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