PAIN GATE THEORY

•Ghalib Hussain Khan•Bs. Physiotherapy •Institute Of Physiotherapy

LUMHS Jamshoro SindhEmail:dr.khan127@gmail.com

• 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.

• 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.

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.

• 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

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

Nociceptors

Mechanism:

Trauma Receptors A-deltaC fibers

Afferent Pathway

ThalamusReticular FormationPAG

CortexHigher centers

“ouch”“mommy”

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.

• 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

• 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.

• 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

• 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 –

?? Questions ??