En anglais

Two doors for one message

Science · The Human Body · ages 19-20

Name ______________________ Date ____________

Which information about a target neuron helps predict whether transmitter binding excites or inhibits it?
- Target receptors, ion gradients and signalling machinery
- Sender receptors, ion gradients and signalling machinery
- Sender axon length, branch number and terminal position
Which statement describes the usual onset of ionotropic and metabotropic responses?
- Ionotropic usually starts slower; metabotropic usually starts faster
- Ionotropic usually starts faster; metabotropic usually starts slower
- Ionotropic and metabotropic usually start with equally rapid responses
In the adult central nervous system, glutamate is the main excitatory transmitter and GABA is the main inhibitory transmitter.
Circle one: True False
The same transmitter reaches two resting neurons. In A, net positive charge enters and moves voltage toward threshold. In B, potassium leaves and moves voltage away from threshold. What are the effects?
- A is excited; B is inhibited
- A and B are both excited
- A is inhibited; B remains as likely to fire
A transmitter binds a metabotropic receptor, but its G protein cannot activate. What happens to the response through this receptor?
- The response proceeds through the inactive G protein
- The response uses a receptor channel that opens directly after transmitter binding
- The usual G-protein-dependent response is blocked despite transmitter binding
At a vesicle-mediated chemical synapse, follow a transmitter molecule that binds a receiving receptor before removal. Which sequence is possible after an impulse arrives?
- Binding, calcium entry, diffusion, vesicle fusion, removal
- Calcium entry, vesicle fusion, diffusion, binding, removal
- Removal, calcium entry, binding, vesicle fusion, diffusion
A student labels two transmitter systems with their taught functions, then asks whether each behaviour has a single chemical cause. Which summary matches the lesson on both points?
- Dopamine: mood and sleep; serotonin: movement and reward learning; several systems contribute to each behaviour.
- Dopamine: movement and reward learning; serotonin: mood and sleep; several systems contribute to each behaviour.
- Dopamine: movement and reward learning; serotonin: mood and sleep; one system accounts for each behaviour.
A synapse removes transmitter mainly by uptake. Uptake is blocked, other removal routes are negligible, and receptors remain responsive. What is the likely effect on released transmitter?
- It leaves the cleft sooner, so receptor signalling may end sooner
- It stays outside just as long, so receptor signalling may last just as long
- It stays outside cells for longer, so receptors may signal for longer

Answer key

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Target receptors, ion gradients and signalling machinery · Receptors on the receiving neuron affect channels and other cellular targets. Ion gradients and signalling machinery help determine whether firing becomes more or less likely.
Ionotropic usually starts faster; metabotropic usually starts slower · Ionotropic receptors open their own channels. Metabotropic receptors use a G-protein relay, so their responses usually begin more slowly.
True · These are their main roles in the adult central nervous system. They do not describe every possible response at every target.
A is excited; B is inhibited · A moves toward firing threshold, making firing more likely. B moves away from threshold, making firing less likely. Thus A is excited and B is inhibited.
The usual G-protein-dependent response is blocked despite transmitter binding · This receptor needs G-protein activation to pass on the signal. Binding alone cannot complete the route when its G protein cannot activate.
Calcium entry, vesicle fusion, diffusion, binding, removal · Calcium entry triggers vesicle fusion and release. The molecule diffuses to a receptor and binds. In this question, its removal comes next.
Dopamine: movement and reward learning; serotonin: mood and sleep; several systems contribute to each behaviour. · The lesson pairs dopamine with movement and reward learning, and serotonin with mood and sleep. Several systems contribute to each behaviour. These examples do not exclude other roles for either transmitter.
It stays outside cells for longer, so receptors may signal for longer · Blocking the main removal route leaves transmitter outside cells for longer. Responsive receptors may signal for longer; endless activity is not guaranteed.