Mechanisms of Pain

Question 1

According to the International Association for the Study of Pain what is pain?

Answer 1

“An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”

Question 2

3 treatment goals in regards to pain

Answer 2

1) Resolve underlying pathology
2) Modify patient’s perception of discomfort
3) Maximize function whether or not the source of pain can be modified

Question 3

Pain is categorized by _____ or ____.

Answer 3

Duration

Source

Question 4

Two types of pain categorized by duration

Answer 4

1) Acute

2) Chronic

Question 5

Two types of pain categorized by source

Answer 5

1) Referred

2) Radiating

Question 6

Acute vs. Chronic Pain

Answer 6

Acute pain lasts less than 6 months whereas chronic pain persists past the normal time for tissue healing (>6 months)

Question 7

The major difference between chronic and acute pain is what??

Answer 7

Acute pain is a reaction to a noxious stimulus and will last as long as this stimulus exists.
Chronic pain persists after the noxious stimuli is gone

Question 8

Referred vs. Radiating Pain

Answer 8

Referred pain is experienced in an area other than the location of the actual tissue damage, whereas radiating pain is caused by irritation of nerves and nerve roots

Question 9

When treating referred pain what is important to keep in mind?

Answer 9

Always treat the joint above and below

Question 10

Are there common referral patterns from internal organs?

Answer 10

Yes, there are common sites of referred pain for specific internal organs

Question 11

5 red flags for referred pain

Answer 11

1) Pain that is not relieved by rest
2) Pain that is not relieved by change of position
3) Pain/symptoms that do not fit an expected mechanical or neuromuscular pattern
4) Pain that increases at night
5) When pain cannot be reproduced, aggravated, or altered in any way

Question 12

Pain is a response to stimulation of _____ _____.structures.

Answer 12

peripheral nociceptive

Question 13

Afferent vs. Effernet nerve fibers

Answer 13

• Afferent nerve fibers transmit impulses from the sensory receptors toward the brain
• Efferent nerve fibers such as motor neurons transmit impulses from the brain toward the periphery

Question 14

What are nociceptors?

Answer 14

free, non-corpuscular peripheral nerve endings

Question 15

2 types of nociceptors

Answer 15

1) C fibers (aka Group IV afferents)

2) A-delta fibers (aka Group III afferents)

Question 16

Describe C fibers

Answer 16

• Small, slow, unmyelinated (1 – 2.5 meters/second)
• Transmit pain sensations that are often described as dull, throbbing, aching, burning, tingling or tapping
• Slow onset, long lasting
• Accompanied by nausea, sweating, incr. BP or HR
• Can be blocked by opioids (morphine, oxycodone, hydrocodone)

Question 17

Describe A-delta fibers

Answer 17

• Small, faster, myelinated (30 meters/second)
• Most sensitive to high intensity mechanical stimulation
• Described as sharp, stabbing, or picking
• Quick onset, last a short time
• Generally not blocked by opioids

Question 18

Pain-transmitting neurons originating in the spinal cord ascend to the thalamus via what tracts?

Answer 18

spinothalamic (ST) tracts

Question 19

In the hypothalamus what tracts relay sharp pain?

Answer 19

Lateral spinothalamic tract (LST)

Question 20

In the hypothalamus what tracts relay prolonged, aching pain?

Answer 20

Anterospinothalamic tract (AST)

Question 21

What type of cell increases muscle spasms?

Answer 21

T-cells

Question 22

How does the Sympathetic Nervous System influence pain?

Answer 22

• SNS involved in producing effects that prepare the body for “fight or flight”
• These hyperactive responses from the SNS can increase the severity of pain and cause symptoms of sympathetic activity

Question 23

What is Complex Regional Pain Syndrome (CRPS)?

Answer 23

an abnormal sympathetic activation caused by a hyperactive response of the sympathetic nervous system to an acute injury, or a failure of the sympathetic response to subside after an acute injury, which can increase pain severity and exaggerate s/s of sympathetic activity

Question 24

3 Pain Theories

Answer 24

• Specificity Theory
• Pattern Theory
• Gate Control

Question 25

What does Von Frey’s Specificity Theory state?

Answer 25

The body has a separate sensory system for perceiving pain and the quality of sensation is dependent upon the nerve’s properties

Question 26

What are Pacinian corpuscles?

Answer 26

pressure receptors, responsible for detecting vibration from steady pressure (quick)

Question 27

What are Merkel’s disks?

Answer 27

touch receptors, responsible for discriminative touch (slow)

Question 28

What are Ruffini endings?

Answer 28

receptors that detect heavy and continuous touch sensations (slow)

Question 29

What are Meissner’s corpuscles

Answer 29

receptors detect light touch and determine the texture of an object (quick)

Question 30

What does Goldschneider’s pattern theory state?

Answer 30

That there is no separate system for perceiving pain, rather the pattern of stimulation is determined whether the brain would interpret the stimulus as pain

Question 31

Many physical agents are thought to work via the what theory? (Ex. TENS)

Answer 31

Gate Theory

Question 32

What does the gate control theory state?

Answer 32

Severity of pain is determined by the balance of excitatory and inhibitory inputs to T cells in the substantia gelatinosa of the spinal cord

Question 33

T cells receive excitatory input from what types of receptors?

Answer 33

C and A-delta nociceptive afferents

Question 34

T cells receive excitatory input from what types of receptors and what other sources?

Answer 34

• A-beta non-nociceptive sensory afferents

- descending neurons from the limbic system, the raphe nucleus and the reticular systems

Question 35

Increased activity of the non-nociceptive sensory afferents cause what 3 things?

Answer 35

• Presynaptic inhibition of T cells
• Effectively closes the spinal gate to the cerebral cortex
• Decreases the sensation of pain

Question 36

Input of large A fibers excited the inhibitory interneuron, thus “____ the gate” and inhibiting ascending nociceptive stimuli

Answer 36

closing

Question 37

Input from small C fibers stimulated the excitatory interneurons tending to “____ the gate” and allowing ascending nociceptive stimuli

Answer 37

open

Question 38

What are Opiopeptins also known as?

Answer 38

Endorphins

Question 39

How do Opiopeptins work?

Answer 39

They control pain by binding to specific opioid receptors in the nervous system.

Question 40

Opiopeptins cause presynaptic inhibition by suppressing the inward flux of _____ ions.

Answer 40

Calcium

Question 41

Opiopeptins cause postsynaptic inhibition by promoting the outward flux of ______ ions

Answer 41

potassium

Question 42

What are the advantages and disadvantages of physical agents when compared to pharmacological agents?

Answer 42

Advantages: Fewer side effects and Long term

Disadvantages: Takes longer, Last for a short period of time, and Requires work