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Chapter 2: Central and Peripheral Nervous System Anatomy and Physiology

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Which of the following pathways is involved in the transmission of pain?

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(A) corticobulbar tract

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(B) corticospinal tract

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(C) lateral spinothalamic tract

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(D) dorsal columns

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(E) medial lemniscus

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The answer is C. The lateral spinothalamic tracts are involved in the transmission of pain, temperature, and touch. As pain fibers enter the spinal cord, they typically cross over to form the lateral spinothalamic tract, meaning that ascending pain transmission carries sensation from the contralateral side.

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Descending pathways involved in control of the motor system include the corticospinal, corticobulbar, corticopontine, rubrospinal, reticulospinal, vestibulospinal, and tectospinal tracts. The dorsal column system is involved in ascending transmission of fine touch, proprioception, and two-point discrimination. The fibers originate in the skin, joints, and tendons and end in the dorsal column nuclei (nucleus gracilis and nucleus cuneatus). A crossed fiber bundle, the medial lemniscus, then projects from these nuclei to the contralateral thalamus. The ventral posterolateral (VPL) thalamic nuclei then send sensory information to the somatosensory cortex.

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Refs: Waxman SG. Clinical Neuroanatomy. 27th ed. New York, NY: McGraw Hill; 2013.

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Hammer GD, McPhee SJ. Pathophysiology of Disease: An Introduction to Clinical Medicine. 7th ed. New York, NY: McGraw Hill; 2014.

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A patient has a lesion involving one half of the spinal cord (Brown-Sequard syndrome). Which of the following best describes the expected deficit?

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(A) contralateral weakness

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(B) ipsilateral impaired vibratory sensation

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(C) contralateral impaired sense of joint position

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(D) ipsilateral impaired pain sensation

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(E) contralateral loss of all sensation

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The answer is B. Brown-Sequard syndrome involves:

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  • Ipsilateral weakness (due to transection of the corticospinal tract).

  • Ipsilateral loss of joint position and vibratory sense (due to transection of the posterior column).

  • Contralateral loss of pain and temperature sense approximately 1 or 2 levels below the lesion (due to transection of the spinothalamic tract.

  • Other signs include unilateral and segmental radicular pain and muscle atrophy.

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Ref: Hammer GD, McPhee SJ. Pathophysiology of Disease: An Introduction to Clinical Medicine. 7th ed. New York, NY: McGraw Hill; 2014.

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The cerebral cortex is made up of 6 lobes. Which of the following lobes is involved in “fight-or-flight” responses?

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(A) frontal

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