Pain Perception

Question 1

Is long lasting pain reversible or irreversible?

Answer 1

long lasting = reversible

persistent = irreversible

Question 2

what receptors detect pain?

Answer 2

nociceptors = free nerve endings responding to mechanical, thermal or chemical stimuli

Question 3

what are Adelta fibers responsible for?

Answer 3

sharp localized immediate pain

-relay info to the thalamus and trigger immediate withdrawal/localization of pain

Question 4

what are C fibers responsible for?

Answer 4

dull/diffuse pain -

Question 5

Describe the conventional 3 neuron pain pathway

Answer 5

• primary pain to spinal cord
• spinothalamic tract to thalamus
• thalamus to sensory cortex

Question 6

where to A delta and C fibers ascend in the spinal cord?

Answer 6

through the tract of lissauer

Question 7

where do Adelta and C fibers synapse with 2nd order neurons?

Answer 7

in the substantia gelatinosa

Question 8

where does decussation of pain/temp information occur?

Answer 8

it occurs over one or two segments (not right away)

Question 9

how do endogenous opiates work?

Answer 9

beta endorphin acts at site that are associated with pain modulation to act on opiod receptors

ie)

mu = heat

delta = mechanical

kappa

Question 10

how do endocannabinoids work?

Answer 10

they work by acting on canabinoid receptors CB1 and CB2

Question 11

what is the gate theory of pain perception?

Answer 11

gate theory suggests that non-painful signals can inhibit transmission of pain signals in the spinal cord

ex) Aalpha/Abeta fibers carrying touch, pressure and vibration can stimulate interneurons in the substantia gelatinosa, inhibiting the transmission of pain at the synpase between 1st and 2nd order neurons

Question 12

describe the following terms

• paresthesia
• dysesthesia
• hyperalgesia
• allodynia

Answer 12

paresthesia = pins and needles

dysesthesia = burning sensation

hyperalgesia = lower pain threshold/exaggerated pain

allodynia = pain in response to non-noxious stimulus

Question 13

Define deafferentation pain and psychogenic pain

Answer 13

deafferentation pain = peripheral nerve lesions such as phantom limb pain

psychogenic pain = occuring with or without an organic cause or disproportionate to the organic cause

Question 14

Q 1. A diagnosis of acute appendicitis is reached in a 20

year old student who presented with pain initially in the

peri-umbilical area moving to the right iliac fossa after

some hours. Describe the physiological mechanism

underlying referred pain and explain why the pain

moves to the right iliac fossa.

Answer 14

physiological mechanism of pain- visceral pain is poorly localized and is referred to somatic structures that share spinal segments as a result (corresponding dermatome)

Once the cause of the visceral pain irritates a somatic structure around it (i.e. the peritoneum), it can localize the pain and the pain then moves away from the dermatome

this patient has appendicitis