Nociception & pain

Define pain (IASP 2020).

An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.

Is pain the same as nociception?

No. Pain and nociception are different phenomena.

Define nociception.

Noxious sensory information transmitted through nociceptor neurons.

Can pain be inferred solely from sensory neuron activity?

No.

What 3 major factors influence pain?

Biological, psychological, and social factors.

What is the purpose of fast pain?

Immediate protective withdrawal response.

What fibers transmit fast pain?

Aδ fibers.

Characteristics of fast pain?

Sharp, pricking, well localized.

What fibers transmit slow pain?

C fibers.

Characteristics of slow pain?

Burning, aching, diffuse, emotionally distressing.

Why is slow pain more emotionally distressing?

It is transmitted via C fibers and associated with limbic system activation.

Do nociceptors adapt to constant stimuli?

No, they continue firing.

Do many sensory nerves adapt over time?

Yes.

What type of pain is generally proportional to stimulus?

Nociceptive pain.

What are the two types of nociceptive pain?

Somatic and visceral.

Give examples of somatic nociceptive pain.

Sprains, strains, fractures, burns.

Characteristics of visceral pain?

Diffuse, poorly localized, emotionally distressing, often referred.

Define neuropathic pain.

Pain caused by damage or disease of neural tissue.

Define peripheral neuropathic pain.

Pain from irritation or damage to a peripheral nerve or nerve root.

Signs of peripheral neuropathic pain?

Radiating pain, paresthesias, dermatomal distribution.

Define nociplastic pain.

Pain caused by dysfunction of the nociceptive system without tissue or nerve damage.

Is nociplastic pain due to nervous system damage?

No.

What is peripheral sensitization?

Increased responsiveness of nociceptors due to inflammation.

What is central sensitization?

Increased CNS responsiveness and amplification of pain signals.

What is referred pain?

Pain perceived at a location different from the source.

Does referred pain follow dermatomes?

Not always. Radicular pain does; sclerotomal pain does not.

What are sclerotomes?

Areas of bone, ligament, tendon, disc, and facet joint innervated by a single spinal segment.

Sclerotomal pain is usually carried by what fibers?

C fibers.

What are nervi nervorum?

Nociceptive nerves that innervate neural connective tissue.

What is paresthesia?

Abnormal sensation such as pins and needles.

What is centralization?

Pain localizes proximally as nerve irritation decreases.

What is peripheralization?

Pain spreads more distally with increased nerve irritation.

Who developed Gate Control Theory?

Melzack and Wall.

What fibers close the gate in Gate Control Theory?

Aβ fibers.

What fibers open the gate?

C fibers.

How does non nociceptive input reduce pain?

By activating inhibitory interneurons in the spinal cord.

Name 3 PT interventions that use Gate Control Theory.

TENS, manual therapy, exercise.

Does Gate Control Theory explain neuropathic pain?

No.

True or False: More pain means more tissue damage.

False.

True or False: Pain only occurs when there is an injury.

False.

True or False: When tissue heals, pain always stops.

False.

What organ cannot sense pain?

The brain (brain tissue itself lacks nociceptors).

What does NOPQRST stand for?

Number, Origin, Palliate/Provocate, Quality, Region/Radiation, Severity/Suffering, Timing/Trend.

What does SOCRATES stand for?

Site, Onset, Character, Radiation, Associations, Time course, Exacerbating/Relieving, Severity.

“No brain, no pain” means what?

Pain requires brain interpretation.