Motor Control: From Intention to Muscle · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

From intention to muscle

Science · The Human Body · ages 21-22
Name ______________________   Date ____________

  1. What does the cortex specify in a reaching movement?

    • Which exact muscle fibres fire
    • What to do and which target to reach
    • The stiffness of the bones

  2. What is a motor unit?

    • One motor neuron plus all the fibres it drives
    • One muscle plus its bone
    • One joint plus its ligaments

  3. Small motor units are recruited before big ones as demand rises.

    Circle one:   True   False

  4. While reaching, who keeps you from toppling over?

    • The cortex picking the target
    • The finger muscles gripping
    • The brainstem tuning posture and gain

  5. You lift a feather, then a heavy bag. What changes in recruitment?

    • Big units fire first for the feather
    • More and bigger units join for the bag
    • The same single unit does both jobs

  6. A patient overshoots targets but has normal strength. Which damage fits?

    • Cerebellar damage
    • A torn muscle
    • A broken bone

  7. Why does corrector damage degrade movement without paralyzing it?

    • Muscles no longer need any commands
    • The cortex, brainstem, and cord still drive the muscles
    • Paralysis only happens in sleep

  8. A patient is stiff and slow with a tremor at rest. Which damage fits, and why?

    • Cerebellar, because balance is wobbly
    • Basal ganglia, because movement is reluctant
    • Spinal, because reflexes are gone
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Answer key

For grown-ups. Fold this page away before handing over the rest.

From intention to muscle W1-mt_hrWOuRtPDl-s1

  1. What to do and which target to reach · The cortex plans the goal; lower levels handle the details.
  2. One motor neuron plus all the fibres it drives · The neuron and its fibres are the smallest command package.
  3. True · Delicate jobs start small; bigger units join for heavier work.
  4. The brainstem tuning posture and gain · Posture control belongs to the brainstem level.
  5. More and bigger units join for the bag · Rising demand recruits bigger units and faster firing.
  6. Cerebellar damage · Clumsy but willing with normal strength marks the cerebellum.
  7. The cortex, brainstem, and cord still drive the muscles · The driving chain survives; only the correction loops fail.
  8. Basal ganglia, because movement is reluctant · Stiffness, slowness, and rest tremor mark basal ganglia trouble.
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