Regional Anatomy of the Central Nervous System · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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Mapping the control centre

Science · The Human Body · ages 19-20
Name ______________________   Date ____________

  1. What do the basal nuclei contribute to voluntary movement?

    • Selecting and scaling voluntary actions
    • Relaying visual signals to cerebral cortex
    • Sending spinal motor axons to skeletal muscle

  2. Which pairing correctly identifies a part of the diencephalon and a part of the brain stem?

    • Diencephalon: cerebellum; brain stem: thalamus
    • Diencephalon: medulla; brain stem: cerebellum
    • Diencephalon: thalamus; brain stem: medulla

  3. Which tissue occupies the central region of a spinal cord cross-section?

    • White matter around the central canal
    • Grey matter around the central canal
    • Grey cerebral cortex around the cord

  4. Which route describes most fibres from right motor cortical areas that enter the lateral corticospinal tract?

    • Cross in the spinal cord, then descend on its right side
    • Cross in the medulla, then descend in the left cord
    • Stay on the right through the medulla and spinal cord

  5. Which route carries vibration information from the right foot toward sensory cortex?

    • Left cord, cross in medulla, then right thalamus and cortex
    • Right cord, cross in thalamus, then left medulla and cortex
    • Right cord, cross in medulla, then left thalamus and cortex

  6. A lesion damages motor neuron bodies in one ventral horn. Which direct effect is expected?

    • Weakness in muscles they supply
    • Loss of sensation throughout the body
    • Loss of visual input from both eyes

  7. Assume one focal CNS lesion. Below a trunk level, the left leg is weak and has lost vibration and position sense. The right leg has lost pain and temperature sensation starting slightly lower. Which region best fits?

    • Left motor cortex of the cerebrum
    • Right half of the spinal cord
    • Left half of the spinal cord

  8. Sensory loss with preserved movement, by itself, proves that a lesion is in an ascending spinal tract.

    Circle one:   True   False

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Answer key

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Mapping the control centre W1-mt_S9f5cUS8NZ-s1

  1. Selecting and scaling voluntary actions · Basal nuclei help select, initiate and scale movements through their connections with other motor regions.
  2. Diencephalon: thalamus; brain stem: medulla · The thalamus is part of the diencephalon. The medulla is part of the brain stem. The cerebellum is a separate major brain division.
  3. Grey matter around the central canal · Grey matter surrounds the spinal cord's central canal. White matter lies outside this central grey region.
  4. Cross in the medulla, then descend in the left cord · Most corticospinal fibres cross in the lower medulla. Those from the right cortex then descend in the left lateral corticospinal tract.
  5. Right cord, cross in medulla, then left thalamus and cortex · Vibration follows the dorsal column pathway. Right-foot input ascends on the right, relays and crosses in the medulla, then reaches the left thalamus and sensory cortex.
  6. Weakness in muscles they supply · Ventral horn motor neurons send axons to skeletal muscles. Damage to those neurons weakens the muscles they supply.
  7. Left half of the spinal cord · The left cord carries left-sided corticospinal and dorsal column signals, plus pain and temperature signals that crossed from the right. Damage there fits the combined pattern.
  8. False · The pattern suggests sensory involvement, but peripheral nerves and other CNS sites can also produce sensory loss. It does not prove a spinal tract location.
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