Synaptic Transmission, Summation and Inhibition · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Votes at the Hillock

Science · The Human Body · ages 17-18
Name ______________________   Date ____________

  1. What links the arriving spike to transmitter release?

    • Sodium leaving through the cleft
    • Calcium entering and fusing vesicles
    • Potassium splitting the transmitter

  2. Put the synaptic steps in order from the arriving spike.

    • Transmitter diffuses, calcium enters, vesicles fuse
    • Calcium enters, vesicles fuse, transmitter diffuses
    • Vesicles fuse, receptors open, calcium enters

  3. How does an inhibitory synapse act on the membrane?

    • It hyperpolarises the membrane away from threshold
    • It depolarises the membrane toward threshold
    • It seals the membrane so nothing changes

  4. Which pair best shows temporal versus spatial summation?

    • Two transmitters mixing in one vesicle
    • One enzyme clearing two clefts
    • A quick double tap from one friend versus several friends pushing together

  5. How does temporal summation differ from spatial summation?

    • Temporal adds repeats from one synapse while spatial adds inputs from several at once
    • Temporal uses inhibition while spatial uses excitation
    • Temporal fires the axon while spatial fires the dendrites

  6. Excitation pushes toward threshold and inhibition pulls away. Who decides?

    • Each vesicle decides on its own
    • The axon hillock adds the votes
    • The myelin sheath takes a vote

  7. Inhibition is simply the absence of excitation. This claim is true.

    Circle one:   True   False

  8. One weak input cannot fire a cell, but five weak inputs together do. Why?

    • Each input widens the cleft for the next
    • Calcium builds up until vesicles burst
    • Their small effects summate at the hillock past threshold
LightMySky · lightmysky.comW1-mt_0uM8xRV92B-s1

Answer key

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

Votes at the Hillock W1-mt_0uM8xRV92B-s1

  1. Calcium entering and fusing vesicles · Calcium entering through voltage gated channels makes vesicles fuse and dump transmitter.
  2. Calcium enters, vesicles fuse, transmitter diffuses · Calcium entry triggers fusion, and fusion releases the transmitter that diffuses across.
  3. It hyperpolarises the membrane away from threshold · Opening chloride or potassium channels moves the membrane further from firing.
  4. A quick double tap from one friend versus several friends pushing together · The double tap repeats one source in time, while several friends add sources across space.
  5. Temporal adds repeats from one synapse while spatial adds inputs from several at once · Temporal piles signals in time, spatial piles them across places.
  6. The axon hillock adds the votes · The hillock sums excitatory and inhibitory inputs and fires only if threshold is reached.
  7. False · Inhibition is active braking that hyperpolarises the membrane away from threshold.
  8. Their small effects summate at the hillock past threshold · Weak inputs add up through summation until their combined total reaches threshold.
Worksheet · LightMySky