Pain Flashcards by Catherine Parkhurst

How do non-nociceptors respond at higher temps?

At the same rate

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What do nociceptors respond to?

Higher temperatures

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What are the two temporal elements of pain, and what fibers are they transmitted by?

1: sharp quick (A delta)
2: more long lasting, less sharp (C)

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How do local anesthetics block pain?

Block Na+ channels to prevent conduction of impulses along C fibers

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What are the components of pain?

Sensory discriminative component
Affective motivational component
Sensitization
Desc. control/central modulation

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What is the sensory discriminatory component of pain? What does it depend on?

Location, quality and intensity of noxious stimulation

Pathways that target somatosensory areas

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What is the affective motivational component of pain?

What does it depend on?

Unpleasant quality of experience –> autonomic

Additional cortical/brainstem pathways

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What is the sensitization of pain?

Hypersensitivity to protect injured area, promote healing and prevent infection

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What is the descending control/central modulation of pain?

Reduces pain perception

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What does the spinothalamic tract transmit about nociceptive pain?

Discriminative aspects of pain/temp: who, what, when

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What does the spinoreticular tract transmit about nociceptive pain?

Emotional/arousal aspects of pain

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What does the spinomesencephalic tract transmit about nociceptive pain?

central modulation of pain: start to feel better

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What is the destination of the spinomesencephalic tract?

Periaqueductal gray, superior colliculus

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What is the destination of the spinoreticular tract?

Amygdala, hypothalamus, reticular formation

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What is the destination of the spinothalamic tract?

Somatosensory cortex

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What are the thalamic relays of the spinoreticular and spinomesencephalic tracts?

Midline thalamic nuclei, intralaminar nuclei

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What are the symptoms of a lesion of the parietal lobe or primary sensory cortex?

contralateral numb tingling or pain

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What are the symptoms of a lesion of the thalamus?

contralateral burning pain

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What are the symptoms of a lesion of the DCMLS?

tingling, numb sensation
tight band-like sensation around trunk or limbs
feeling of gauze on fingers
electricity sensation down back and extremities upon neck flexion = Lhermite’s sign

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What are the symptoms of a lesion of the STT pathway?

sharp, burning or searing pain

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What are the symptoms of a lesion of the nerve roots?

Radicular pain with numbness and tingling in dermatomal distribution = radiculopathy

What are some causes of sensory neuropathies?

Diabetes
Immune disorders
Mechanical
Varicella/Herpes Zoster
Infectious disorders
HIV, CMV, Hep B, toxins, malnutrition

How does Guillain Barre cause sensory neuropathy?

Demyelination following viral infection –> paresthesia

What is neurapraxia?

Mild insult causing temporary impairment of nerve conduction

What is Causalgia/complex regional pain syndrome?

incomplete regeneration causing burning sensation, edema

What is neuralgia?

Severe persistent pain in the distribution of a cranial or spinal nerve

What are the symptoms of trigeminal neuralgia?

Lancinating paroxysms, trigger zones, unilateral, symptom free between attacks

How does varicella/herpes zoster cause sensory neuropathy?

Increases excitability of sensory neurons in DRG resulting in low threshold of firing and spontaneous activity

What do recessive mutations in sodium channels cause?

Loss of function: congenital insensitivity to pain (CIP)

What do dominant mutations in sodium channels cause?

Gain of function: inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD)

What is sensitization?

Following repeated application of noxious stimuli, neighboring nociceptors that were not responsive, now become responsive

What is hyperalgesia?

phenomenon of stimuli that are normally perceived as slightly painful as signficantly more painful

What is allodynia?

The induction of pain by what is normally an innocuous stimulus

What is the goal of sensitization?

Protects injured area promotes healing prevents infection

What causes sensitization?

Changes in sensitivity of: - peripheral nociceptive receptors - central targets

What is peripheral sensitization?

interaction of nociceptors with the "inflammatory soup" of substances to decrease threshold of activation for nociceptors (fire more easily)

How do prostaglandins interact with nociceptors?

Increase response of nociceptive fibers

How does capsaicin work?

Repeated application of capsaicin causes desensitization of C fibers and depletes substance P to block peripheral sensitization

What are some therapeutic uses of capsaicin?

Arthritis Mastectomy Neuralgia Shingles

What channels in C fibers can be moderated for an analgesic effect?

VR1 / TRPV1 channels in C fibers are activated by moderate heat (45 degrees C) and capsaicin

What is central sensitization?

immediate, activity dependent increase in excitability of neurons in dorsal horn of SC following high levels of activity in nociceptive afferents to increase pain sensitivity

What is the transcription-independent mechanism of central sensitization?

Windup = lasts only during stimulation (acute)

What is the transcription-dependent mechanism of central sensitization?

Allodynia: outlasts stimulus for hours and can be mediated by COX (chronic) - development/increase in spontaneous activity reduction of threshold of activation by peripheral stimuli - expansion of receptive field size (respond to innocuous and noxious stimuli)

What are two ways that the descending control of pain perception works?

1 stress induced analgesia | 2 placebo effect - physiological response following administration of inert remedy

How can one block the effects of a placebo effect?

Naloxone: inhibitor of opiate receptors

How do endogenous opioids work?

Inhibit nociceptors

What is the gate theory of pain?

local modulation of nociceptive information: pain results from the balance of activity in nociceptive and non-nociceptive afferents

How does visceral pain transmit to the cortex? What is the pathway?

DRG relay point 1: dorsal column ipsilaterally of SC relay point 2: medulla via gracile nucleus DECUSSATES in medulla, crossing medial lemniscus relay point 3: ventral posterior nuclear complex of thalamus Terminates in insular cortex

What are 2 surgical interventions for intractable pain, and what are they used for?

1 midline myelotomy: visceral pain | 2 cordotomy for cutaneous pain

What is a midline myelotomy and what is it used for?

1 midline myelotomy for visceral pain: cut neurons

What is a cordotomy and what is it used for?

2 cordotomy for cutaneous pain: lateral funiculus from dentate ligaments to line of ventral rootlets several segments rostral to the highest dermatomal level of pain

Why does referred pain occur?

Visceral pain is also conveyed centrally by neurons that contain cutaneous pain!