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Transcript
SOMATIC SENSORY SYSTEM I. TRUE or FALSE. Circle the T or F as appropriate. T F 1. Endogenous regulation of pain signals involves a "gating" mechanism in the substantia gelatinosa. T F 2. The largest diameter sensory fibers innervate muscle spindles and tendon organs, but not the skin. T F 3. Group III afferent fibers mediate slow pain. T F 4. Some of the primary sensory fibers entering the pons with the trigeminal nerve make synapses in the lower medulla. T F 5. All Group III and IV sensory fibers terminate as free nerve endings. T F 6. At the level of the upper medulla, the medial lemniscus is found near the midline, medial to the inferior olive. II. MULTIPLE CHOICE. Circle every correct answer. There may be more than one correct answer per question. 1. Relatively high cutaneous receptor density is found in a. the skin of the back of the neck b. the skin of the lips c. skin receiving an exaggerated cortical representation (i.e., relatively high cortical magnification) d. skin whose primary cutaneous afferents have relatively large receptive fields e. skin in which two-point discrimination thresholds are relatively low (i.e., spatial acuity is good) 2. Free nerve endings can serve as receptors for the sensations of a. b. c. d. e. fast pain touch warmth cold slow pain 3. A dissociated sensory loss (a loss affecting some somatic sensory submodalities and not others) could arise from a. b. c. d. e. destruction of dorsal root ganglia destruction of the precentral gyrus a lesion restricted to the dorsal columns an infarction affecting the midline of the medulla a disease process interrupting the anterolateral quadrant of the spinal white matter 4. Highly discrete localization of cutaneous stimuli is mediated in part by the a. b. c. d. e. anterolateral system spinal trigeminal nucleus dorsal column-medial lemniscus system main (principal) nucleus of the fifth cranial nerve lateral lemniscus 5. At the level of the medulla, fibers of the spinothalamic tract a. b. c. d. e. lie lateral to the fibers of the medial lemniscus make synapses in the reticular formation have arisen from cells in the dorsal column nuclei have arisen from cells in the dorsal horn of the spinal cord decussate (cross the midline) 6. Gating of pain impulses by the central nervous system occurs first in the a. b. c. d. e. dorsal column nuclei substantia gelatinosa dorsal root ganglion dorsal nucleus of Clarke anterior white commissure 7. The perceptual quality or modality associated with activity in a particular nerve fiber is determined by a. b. c. d. e. the physical nature of the stimulus the specialization of the receptor endings the degree of myelinization of the nerve fiber the central connections of the nerve fiber the duration of action potentials in the nerve fiber 8. Cutaneous nerve fibers selectively sensitive to temperature a. b. c. d. e. are all myelinated are all unmyelinated terminate peripherally as free nerve endings terminate peripherally as Pacinian corpuscles synapse centrally in the dorsal horn of the spinal cord 9. Two point discrimination is most acute, i.e. the resolvable points are closest together, in regions of skin a. b. c. d. e. having the highest receptor density innervated by fibers with the broadest distribution of sensory terminals innervated by Group I (A alpha) afferents associated with the smallest receptive fields among cells in the postcentral gyrus having the most largest magnification in somatic sensory cortex 10. Primary sensory fibers enter the spinal cord a. b. c. d. e. via the dorsal roots via the ventral roots via the internal capsule via the cauda equina via the thalamus 11. The ability to make fine discriminations in the position of the right arm would be lost following damage to a. b. c. d. e. the spinal roots on the left at cervical levels the spinal roots on the right at thoracic levels the dorsal columns on the right at upper cervical levels the ventral posterior nucleus of the left thalamus the medial lemniscus on the left side of the brainstem 12. "Fast" and "slow" pain are mediated respectively by a. b. c. d. e. group A-delta and group C afferents group III and group IV afferents large and small unmyelinated fibers dorsal columns and spinothalamic tracts neospinothalamic and archispinothalamic projections 13. In the skin's response to injury (triple response of Lewis), an axon reflex (antidromic impulse propagation down branches stimulated afferents) appears to be responsible for the a. b. c. d. e. local swelling of the skin pain flare (widespread vasodilation) local reddening placebo effect 14. Soap gets in your right eye. Which of the following structures participate in the sensation of pain that results? a. b. c. d. e. optic nerve trigeminal nerve main sensory nucleus of fifth nerve spinal nucleus of fifth nerve ventral posteromedial nucleus of the thalamus 15. Electrical stimulation in the periaqueductal grey causes analgesia via a pathway a. b. c. d. e. in which endogenous opioid compounds are involved involving the nucleus raphe magnus and dorsolateral columns involving the corticospinal tract and intermediolateral cell column in which serotonergic cells participate probably involved in the analgesic placebo effect 16. The first synapse in the main spinal pathway for epicritic sensation occurs a. b. c. d. e. in the spinal cord in the dorsal columns in the dorsal column nuclei in the medulla in the thalamus 17. The first synapse in the spinal pathways for protopathic sensation occurs a. b. c. d. e. in the dorsal root ganglia in the dorsal horn in the anterolateral funiculus in the zone of Lissauer in the medulla 18. Neurons in the dorsal column nuclei (nucleus gracilis and nucleus cuneatus) emit axons that can be found in a. b. c. d. e. the medial lemniscus the medial longitudinal fasciculus the medulla the pons the midbrain SOMATIC SENSORY I. True or False 1. 2. 3. 4. 5. 6. T T F T T T II. Multiple Choice 1. 2. 3. 4. 5. 6. 7. b, c, e a, b, c, d, e c, d, e c, d a, b, d b d 8. c, e 9. a, d, e 10. a, b, d 11. c, d, e 12. a, b, e 13. c 14. b, d, e 15. 16. 17. 18. a, b, d, e c, d b a, c, d, e