Pain

Question 1

What is analgesia?

Answer 1

Pain relief and attenuation

Question 2

What is hyperalgesia?

Answer 2

Increasing pain stimulus from source.

Stimulus provided by noxious mechanical, thermal or chemical input

Question 3

What is allodynia?

Answer 3

Abnormal response to touch caused by lesion or trauma to nerve or CNS

Question 4

What is the difference between somatogenic and psychogenic pain?

Answer 4

Somatogenic pain is associated with a known cause due to nociceptor or neuropathy.

Psychogenic is not due to a known physical cause

Question 5

What causes nociceptive pain?

Answer 5

Mechanically gated sodium channels in the skin get opened which triggers an action potential and pain results.

Question 6

What causes neuropathic pain?

Answer 6

Pain activated by neuron in the brain along the nociceptive pathway

Question 7

What causes nociceptive pain?

Answer 7

Activity in neural pathways in response to potentially tissue-damaging stimuli

Question 8

What causes neuropathic pain?

Answer 8

Primary lesion of dysfunction in the nervous system

Question 9

What are the classes of pain?

Answer 9

Pricking, stabbing, pinching (mechanical)

Burning, freezing (thermal)

Aching, stinging, soreness (chemical)

Visceral (mechanical, chemical)

Question 10

What does the emotional component of pain affect?

Answer 10

Pain tolerance

Question 11

What causes sharp and well localized pain?

Answer 11

Fast pain transmitted by myelinated axons (A-delta fibers) with glutamate neurotransmitters

Question 12

What causes dull aching pain that is not well localized?

Answer 12

Slow pain transmitted by unmyelinated axons (C fibers) [1m/s] and substance P neurotransmitter

Question 13

What kind of pain is visceral pain?

Answer 13

Very poorly localized and referred pain

Question 14

What receptors are responsible for cold pain?

Answer 14

TRPM8

Question 15

What receptors are important for mechanical pain?

Answer 15

MDEG

DRASIC

TREK-1

Question 16

Does perception of temperature come from nociceptors for heat and cold?

Answer 16

No

Question 17

What triggers chemical nociceptors?

Answer 17

Exogenous chemicals that penetrate skin such as acid, alkali, and organic molecules.

Intracellular molecules released by cell injury such as cations, peptides/neurotransmitters, prostaglandins, histamine, and bradykinin (chemicals released by mast cells)

Pathological substances released by diseased tissue

Toxins

Question 18

What are polymodal nociceptors?

Answer 18

Pain receptors that are receptive to all kinds of painful stimuli.

They have both slow and fast pain fibers to conduct both fast and slow pain.

Question 19

What effects do inflammatory chemicals have?

Answer 19

They cause an increase in sensitization to pain. Meaning more pain will be produced.

This is due to creation of lower threshold for nociceptor firing. (hyperalgesia)

Question 20

What tracts do pain receptors ascend through?

Answer 20

The anterior spinothalamic tract.

Question 21

Where do pain fibers decussate?

Answer 21

Immediately after synapsing on the 1st lamina of the dorsal horn of the spinal cord they enter.

Question 22

Which part of the brain does the anterior spinothalamic tract go carrying pain signals?

Answer 22

Carries information to the midbrain, thalamus, and mostly the somatosensory cortex

Question 23

What path does pain sensation take from nociceptor to brain?

Answer 23

1st order neuron carries information to dorsal horn lamina I where it meets a second order neuron that decussates immediately and goes up to the brainstem (90% of fibers continue directly to the somatosensory cortex)

Question 24

What is the name of the pain directing part of the anterolateral spinothalamic tract?

Answer 24

The neospinothalamic tract.

Question 25

What kind of pain is carried by neospinothalamic tract?

Answer 25

This tract carries fast pain (sharp pain) A-delta fibers synapse

Question 26

Where does the paleospinothalamic tract run?

Answer 26

Through the anterolateral spinothalamic tract to the brainstem where it stimulates the reticular formation, pons, limbic system, midbrain, and PAG.

Question 27

What pathway does the paleospinothalamic tract follow?

Answer 27

C fibers synapse with neurons in 2nd and 3rd laminae of dorsal horn. Short fibers project to lamina V and 2nd order neurons decussate. Fibers ascend anterolateral spinothalamic tract to the brainstem and most fibers branch from the brainstem.

Question 28

Where do paleospinothalamic fibers branch at the brainstem?

Answer 28

Reticular formation Pons Limbic system Mid Brain PAG (More synapses to lower brain structures) <10% of C fiber signals reach sensory cortex

Question 29

What kind of pain is conveyed by the paleospinothalamic tract?

Answer 29

Slow, burning pain.

Question 30

Which nuclei in the somatosensory cortex contain sharp pain?

Answer 30

Ventral pesterolateral/ventral posteromedial nuclei. (Pain is more localized to a particular body site based, sensory humunculus)

Question 31

Where does slow pain sensation from cold, heat or stab sensation go?

Answer 31

Ventromedial posterior cortex and dorsal insular cortex.

Question 32

Where does emotional reaction to slow pain take place?

Answer 32

Medial dorsal to anterior cingulate cortex

Question 33

Where does physical response and subjective memory of pain take place?

Answer 33

Hypothalamus and limbic cortex

Question 34

What regions of the brain are slowed down by efferent analgesic system?

Answer 34

Periaqueductal grey matter region (midbrain) Locus coeruleus (pons) Nucleus raphe magnus (medulla)

Question 35

What does the efferent analgesic system do?

Answer 35

Activates anti-nociceptive pathways

Question 36

Which part of the spinal cord is the efferent analgesic system located at?

Answer 36

Dorsal horn

Question 37

How does the efferent analgesic system diminish pain sensations?

Answer 37

It releases neurotransmitters that inhibit or block transmission of nociceptive signals (opioids (enkephalins + endorphins and neurotransmitters like serotonin, noradrenaline)

Question 38

What is the gate-control theory?

Answer 38

Pain can be suppressed in the dorsal horn level Normally inhibitory interneurons inhibit ascending pathways for pain resulting in less pain coming up to the brain. Strong stimulus results in inhibition of the inhibitory interneuron thus increasing the pain rising to the brain. (the inhibition of the inhibitory interneuron is caused by a branch of the neuron attached to the nociceptor. Touching another non-painful stimulus results in another stimulatory fiber that acts on the inhibitory interneuron creating more inhibition of painful signal reaching the brain.

Question 39

What are the kinds of interventions that can act on pain signals?

Answer 39

Opiates act centrally by inhibiting neurotransmission of afferent neurons. alpha2-adrenergic agonists act centrally and stimulate endogenous anti-nociceptive neurones Local anaesthetics block Action Potential conduction in nociceptive nerve fibers (ion channel inhibitors) Anti-inflammatory drugs + aspirit reduce hyperalgesia and allodynia

Question 40

How do centrally acting analgesics work?

Answer 40

Potentiating descending analgesic system.

Question 41

How can peripheral pain signals be reduced?

Answer 41

Decreasing prostaglandin production Decreasing hyperalgesia caused by inflammation. Or block ion channels

Question 42

What is congenital analgesia?

Answer 42

Nociceptive stimuli are not processed or integrated at level of brain (patient does not feel pain)

Question 43

What is congenital sensoric neuropathy?

Answer 43

Nociceptive stimuli are not transmitted by peripheral nerves or by spinal afferent tracts (patient does not feel pain)