Understanding Pain and Its Mechanisms

Pain

Unpleasant sensory and emotional experience from tissue damage.

think about how our response affects patients response

Manifestation of Pain

Wide range of sensations

ask patient to describe it to us first

burning

throbbing

tingling

prickly

itchiness

other odd - strings pulling, water running on skin, ants crawling on skin

Sensory Neurons

Neurons labeled by order in sensory chain

First Order Neurons

Transmit signals from receptors to dorsal horn.

Second Order Neurons

Transmit signals from dorsal horn to thalamus.

Third Order Neurons

Transmit signals from thalamus to cerebral cortex.

cerebral cortex interprets messages sent out

Nociceptors

Specialized nerve endings responding to damaging stimuli.

sensory receptors

activate A delta and C nerve fibers

A delta

larger and faster

relay signal to CNS

interprested as pain

C fibers

smaller and slower

relay signals to CNS

interpreted as pain

Nociception

Ability to feel pain

caputures protentially damaging signlas

relay signals to the CNS

interpret as pain

Nociception vs Pain

Nociception is objective event; pain is subjective, emotional experience.

pain results from...

modulation of nociception by a host of factors

heredity

psychosocial experience

prior pain experience

general life stress

Types of Nociceptors

Cutaneous, somatic, visceral

based on location.

most common by function

mechanical nociceptors

lightly mylenated A delta fibers

high threshold

polymodal nociceptors

unmyelinated c fibers

common noxious stimuli

Mechanical (pressure on nerve due to swelling or muscle spasm, most common in sports medicine), thermal, electrical, and chemical pain triggers.

Pathway of Pain Signals

Injury site to dorsal horn via electro-chemical impulse (1st)

up spinal cord to thalamus where heat, cold, touch, and pain first become conscious (2nd)

then to cerebral cortex where the exact location and intensity of the pain are determined, person orally or physically expresses discomfort (3rd)

like a relay

Gate Control Theory

Spinal mechanism allowing one sensation at a time.

located in dorsal horn

whichever one is "louder"

inhibitory mechanism located in the substantia gelatinosa

SG inhibits T cells

Enkephalin

andogenous Opioid-like molecule blocking pain signal transmission.

found in brain, spinal cord, gut

half life only few seconds, no ciculation

thought to block gate by interfering with a delta fiber and cfiber signal transmission to t cells

released through non painful sensory stimulus

Endorphin

Endogenous morphine-like molecule reducing pain perception.

released when injured, take pain away

produced in pituitary and circulated through body

inhibits pain signal transmission and decreases chemical irritants in CNS

may be released by acupuncture and other

endorphin and enkephalin speculation

why ppl experience more pain than others

perhaps more people espeacially sensitive to pain have enkephalin or receptor deficiency

placebo effect may be increased by enkephalin and endorphin

Descending Endogenous Opiate Theory

efferent pathway

operates at supraspinal levels and spinal gate

originates from above

pain signal blocked on way out vs in

Central Control Trigger Theory

aka central biasing theory

pain is not just a simple response to injury but is influenced by the brain and spinal cord. According to this theory, signals from the body (like injury or pressure) are filtered through a "gate" in the spinal cord, and the brain can control whether those signals are felt as pain or not — kind of like a volume dial for pain.

Pain Perception

Multifaceted experience often confused with other sensations.

decrease pain means decrease neural inhibition

treat pain in order to treat other things

Pain vs Pain Perception

Pain is brain's response to noxious stimuli.

as healing progresses, noxious stimuli decline and pain sensation diminishes until minimal or absent

Variability of Pain Tolerance

Pain response varies between individuals and situations.

difficult to research because pain is subjective

hard to describe pain

Pain Management

a complex, tailored approach needed for each patient and injury.

be able to adjust from patient to patient