Synaptic Plasticity and the Molecular Rules of Change · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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How synapses change strength

Science · The Human Body · ages 19-21
Name ______________________   Date ____________

  1. A suitable co-agonist is bound. Which glutamate receptor channel admits calcium when glutamate binding overlaps with enough depolarisation to relieve its magnesium block?

    • The glutamate-binding NMDA receptor
    • The glutamate-binding AMPA receptor
    • The voltage-gated calcium channel

  2. A synapse follows the common timing rule taught here. Repeatedly, its input spikes shortly before the target cell spikes. What change does this favour?

    • It will tend to become weaker
    • It will remain permanently unchanged
    • It will tend to become stronger

  3. LTP names a lasting increase in synaptic strength, while LTD names a lasting decrease.

    Circle one:   True   False

  4. Calcium enters a receiving cell through NMDA receptors. You have not measured the calcium signal's pattern or the later synaptic response. What can you conclude?

    • Calcium entry alone does not identify LTP or LTD
    • Calcium entry proves that lasting strengthening has occurred
    • Calcium entry proves that lasting weakening has occurred

  5. A synapse follows the common timing rule taught here. A repeated close-pair protocol changes from input-before-target spikes to target-before-input spikes. What does the new order favour?

    • LTP, a lasting increase in strength
    • LTD, a lasting decrease in strength
    • No change, regardless of further activity

  6. A synapse adds working AMPA receptors. The same glutamate test pulse now opens more of these channels. Recording conditions are unchanged. What change in the fast excitatory current is expected?

    • A smaller current in the receiving membrane
    • No change in current despite more channels opening
    • A larger current in the receiving membrane

  7. Glutamate and a co-agonist are bound to NMDA receptors. Summed inputs sufficiently depolarise the local membrane without a target spike. A classmate says calcium entry is impossible. Which reply fits the mechanism?

    • Local depolarisation can allow calcium entry
    • A target spike is required for any calcium entry
    • Glutamate always removes the magnesium block

  8. Repeated input-before-target pairs are followed by LTP. Sam says this proves that the recorded input alone caused every target spike. Which conclusion fits the observations?

    • That input was the sole cause of every spike
    • Other inputs may also have contributed
    • That input played no part in any target spike
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Answer key

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

How synapses change strength W1-mt_HldevO4Lzw-s1

  1. The glutamate-binding NMDA receptor · NMDA receptors have the stated binding requirements and voltage-dependent magnesium block. Sufficient local depolarisation permits calcium entry.
  2. It will tend to become stronger · Under the stated rule, repeated close input-before-target pairs favour LTP, a lasting increase in synaptic strength.
  3. True · The statement gives the definitions of LTP and LTD. These names describe outcomes, not one universal firing pattern.
  4. Calcium entry alone does not identify LTP or LTD · NMDA-dependent calcium signalling can support different outcomes. Entry alone does not establish a lasting strength increase or decrease.
  5. LTD, a lasting decrease in strength · For the stated rule, reversing the pairs to target-before-input favours LTD, a lasting decrease in synaptic strength.
  6. A larger current in the receiving membrane · More activated AMPA receptor channels can carry a larger fast excitatory current under the matched conditions stated.
  7. Local depolarisation can allow calcium entry · Sufficient local depolarisation can relieve the magnesium block. With the binding conditions met, a target spike is not mandatory for calcium entry.
  8. Other inputs may also have contributed · The timing and later LTP do not establish sole causation. Other inputs may have helped depolarise the receiving cell.
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