Chapter 10: Pain

8. The placebo effect on pain can be blocked by naloxone. What does this observation reveal about the placebo effect?

Answer: Naloxone is an opioid receptor antagonist. Since naloxone can block the pain-relieving effect of a placebo, the placebo effect appears to exert its effect by activating endogenous opioid receptors.

1. What is the evidence that nociception is mediated by specific nociceptors rather than by strong stimulation of somatosensory receptors or non-nociceptive thermoreceptors?

Answer: Transcutaneous nerve recording experiments have revealed that nociceptors and thermoreceptors respond differently to the same stimulus. Thermoreceptors reach their maximum firing rate at a temperature below the pain threshold and maintain that rate even at increasing levels of heat stimulation, whereas nociceptive thermoreceptors begin firing at a higher stimulus intensity and increase their firing rate as the stimulus intensity increases.

1. Which pathway represents a route that pain information could take in the nervous system? a. Free nerve ending nociceptor, unmyelinated C fiber axon, spinal cord b. Free nerve ending nociceptor, myelinated C fiber axon, spinal cord c. Unspecialized, unmyelinated A axon, spinal cord d. Specialized pain receptor, partially myelinated A axon, brainstem e. Mechanoreceptor, myelinated axons, cranial nerve, spinal cord

Answer: a

12. Disruption of the _______ system prevents the transmission of _______ information. a. dorsal column-mediated lemniscal; visceral pain b. anterolateral; vibration c. dorsal column-mediated lemniscal; temperature d. anterolateral; visceral pain e. anterolateral; mechanosensory

Answer: a

16. Which statement about phantom limbs and phantom limb pain is false? a. Phantom limb sensation occurs in only a very small fraction of amputees, since illusory phantom limbs are rare. b. Phantom limb sensation and pain can occur transiently after local nerve block. c. Phantom limb sensation and pain are not relieved by ablations of the spinothalamic tract or sensory cortex. d. Phantom limb sensations can occur in children born without limbs. e. Mirror box therapy can offer relief for some individuals that experience phantom limb pain.

Answer: a

18. What is the basis of the windup form of central sensitization? a. Summation of slow postsynaptic potentials in the dorsal horn neurons b. Elevation of intracellular Ca2+ levels in the dorsal horn neurons c. Elevation of intracellular Cl- levels in the dorsal horn neurons d. Increase in transcription of the COX-2 enzyme e. Increase in production of chemokines by astrocytes

Answer: a

23. Which statement correctly summarizes the gate theory of pain? a. Flow of ascending pain information is modified by stimulation of low-threshold mechanoreceptors. b. Flow of ascending pain information is modified by stimuli from cortical centers. c. Flow of ascending pain information is modified by stimuli from brainstem centers. d. Descending inputs from pain centers indirectly modify the activity of dorsal horn projection neurons by acting on local circuit neurons. e. Descending inputs from pain centers directly modify the activity of dorsal horn projection neurons.

Answer: a

3. Which statement about TRP receptors is false? a. TRP channels are very specialized and found only in the pain system. b. TRP channels were discovered in studies of Drosophila phototransduction. c. TRPV1 receptors are sensitive to capsaicin and moderate heat. d. TRPV1 receptors might be activated by endogenous compounds that are structurally related to capsaicin. e. TRP channels structurally resemble voltage-gated potassium channels.

Answer: a

13. Colon cancer pain has been shown to be relieved by disruption of the visceral pain pathway at the level of the a. spinal cord near the midline at the sacral level. b. spinal cord near the midline at the thoracic level. c. ventral horn ipsilateral to the site of pain at the thoracic level. d. dorsal horn contralateral to the site of pain at the thoracic level. e. insular cortex ipsilateral to the site of pain.

Answer: b

18. Which statement regarding the descending control of pain is false? a. Electrical and pharmacological stimulation of certain midbrain regions can alleviate pain. b. Insertion of acupuncture needles into the periaqueductal gray produces the same effect as electrically stimulating it. c. The cholinergic, dopaminergic, histaminergic, serotonergic, and noradrenergic systems all contribute to descending control of pain. d. Descending pathways can exert both excitatory and inhibitory influences on the activity of dorsal horn neurons. e. Descending control is mediated by synaptic contacts onto dorsal horn projection neurons, nociceptive afferents, excitatory and inhibitory interneurons, and the synaptic terminals of other descending pathways.

Answer: b

19. Phantom pain is an example of a. allodynia. b. neuropathic pain. c. peripheral sensitization. d. potentiation. e. hallucination.

Answer: b

3. Refer to the graph. Which conclusion about the neuronal basis of pain is consistent with the graph? a. Stimuli of certain temperatures can activate nociceptors but not thermoreceptors. b. These nociceptors respond only to stimuli that are sufficiently warm (approximately 43°C or above). c. There is a linear relationship between thermoreceptor response and temperature of the stimulus. d. The nociceptors and thermoreceptors respond to a thermal stimulus by decreasing the frequency of action potentials e. Any thermal stimulus can activate both the nociceptors and the thermoreceptors.

Answer: b

4. Which fibers conduct the sensation of first pain? a. Unmyelinated C b. Myelinated Aδ c. Myelinated Ia d. Unmyelinated II e. Myelinated Aβ

Answer: b

5. Which sensation would an individual with anesthetized C fibers report when exposed to intense heat? a. Sharp pain followed by a dull burning b. Sharp pain only c. Dull burning only d. Tingling e. No sensation

Answer: b

6. Which channel is responsible for transmitting information about chemical irritants, such as components of cigarette smoke, in the environment? a. TRPV1 b. TRPA1 c. TRPV4 d. Piezo 2 e. ASIC3

Answer: b

7. ASIC channels are involved in generating the sensation of pain associated with heart attack because, during heart attack, a. pH of the tissue increases, which activates the channels. b. pH of the tissue decreases, which activates the channels. c. heart tissue undergoes necrosis, the products of which activate the channels. d. heart muscle contracts, and this mechanical force activates the channels. e. capsaicin produced in the heart muscle activates the channels.

Answer: b

14. Pruriceptors are a. signals emanating from the central autonomic nuclei. b. receptors that convey the affective nature of unpleasant or noxious stimuli. c. subsets of C fibers that are activated by itch-inducing stimuli. d. receptors concerned with the physiological states of the body. e. receptors involved in local motor pattern generation within visceral organs.

Answer: c

20. Refer to the figure. Touching which body part, on a person who is missing his right hand, is most likely to evoke a sensation of being touched on his right fingers? a. Right eye b. Scalp c. Right shoulder d. Right leg e. Left jaw

Answer: c

21. Which statement about placebos is most accurate? a. Studies of the placebo effect prove that some people are imagining they feel pain. b. The use of placebos is a relatively new strategy for treating pain. c. Placebos relieve pain in some people by stimulating endogenous opioid receptors. d. In a study of patients with postoperative wounds, the placebo effect was shown to be ineffective in 75% of subjects given sterile saline as the placebo. e. None of the above

Answer: c

25. In which region of the brain can all three endogenous opioid peptides be found? a. Rostral ventral medulla b. Dorsal horns of the spinal cord c. Periaqueductal gray matter d. Amygdala e. Insula

Answer: c

8. What makes neurons of Rexed's lamina V a likely substrate for referred pain? a. They receive nociceptive information. b. They receive somatosensory information. c. They receive converging information from somatosensory and nociceptive axons. d. They project directly to cortical structures. e. They receive descending inputs from the locus coeruleus.

Answer: c

11. The small receptive fields of SI nociceptor neurons make possible the a. perception of affective-motivational aspects of pain. b. perception of extreme pain. c. perception of weak pain. d. precise localization of pain. e. All of the above

Answer: d

17. Is it possible for an innocuous stimulus, such as touch, to evoke a sensation of pain? a. No, because the different types of information travel through separate pathways. b. No, because an innocuous stimulus is not strong enough to evoke pain sensation. c. Yes, because pain and touch information share a common pathway. d. Yes, it occurs by means of central sensitization. e. Yes, it occurs by means of peripheral sensitization.

Answer: d

9. Which deficit would a lesion restricted to the right side of the spinal cord produce? a. Mechanosensory deficit on the right side of the body only b. Mechanosensory deficit on the left side of the body only c. Pain deficit on the right side of the body only d. Pain deficit on the left side and mechanosensory deficit on the right side of the body e. Pain deficit on the right side and mechanosensory deficit on the left side of the body

Answer: d

10. Which statement does not express one of the observations that contributed to the concept of a dorsal column pain pathway? a. Spinal afferents project to the spinal intermediate gray matter. b. Intermediate gray axons project through the dorsal columns. c. Ventral posterior lateral nucleus and gracile nucleus neurons respond to noxious stimuli. d. Ventral posterior lateral nucleus and gracile nucleus pain responses are lost after a dorsal column lesion. e. Tactile sensations, but not pain sensations, are lost after the infusion of nociceptive inhibitors into the spinal intermediate gray region.

Answer: e

10. Which structure contributes to the sensory-discriminative aspect of pain? a. Anterior cingulate cortex b. Ventral posterior medial nucleus of thalamus c. Ventral posterior lateral nucleus of thalamus d. Amygdala e. Ventral posterior medial and lateral nuclei of the thalamus

Answer: e

14. Where are the bodies of first-order neurons that conduct pain and thermal information from the face located? a. Pars interpolaris b. Ventral posterior medial nucleus c. Brainstem d. Thalamus e. Trigeminal ganglia and ganglia of cranial nerves VII, IX, and X

Answer: e

15. Which perception is an example of hyperalgesia? a. Pain following a small paper cut b. Pain following sunburn c. Sensitivity to innocuous stimulus like the sound of scratching a plate with a fork d. Increased sensitivity to light during a migraine episode e. Increased sensitivity to temperature after sunburn

Answer: e

16. Which mechanism contributes to peripheral sensitization following tissue damage? a. Release of peptides and neurotransmitters from nociceptors b. Migration of immune cells to the site of damage c. Release of proinflammatory substances by the non-neuronal cells d. Potentiation of nociceptors by soluble proinflammatory substances e. All of the above

Answer: e

2. What do nociceptor neurons and non-nociceptor somatosensory neurons have in common? a. Unspecialized nerve endings b. Specialized nerve endings c. Conduction velocity d. Highly-myelinated axons e. Cell body located in the dorsal root ganglia

Answer: e

22. Which center has the highest order within the system that modulates the transmission of ascending pain signals? a. Raphe nuclei b. Locus coeruleus c. Parabrachial nucleus d. Medullary reticular formation e. Midbrain periaqueductal gray matter

Answer: e

24. Receptors to which class of molecules are also found on microglia? a. Exogenous opiates b. Enkephalines c. Endorphins d. Dynorphins e. Endocannabinoids

Answer: e