Explain drug effects on signaling
Predict how a drug changes a synapse: an agonist boosts the signal, an antagonist blocks it: and how myelin speeds the signal along.
- What a synapse does: A drug acts at the synapse, so you must know a synapse is the gap where one neuron passes a chemical signal (neurotransmitter) to the next.
- Signals can be stronger or weaker: Understanding 'boost' vs 'block' depends on knowing a signal between neurons can be increased or reduced.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
At a synapse, an agonist mimics or boosts the neurotransmitter to increase the signal, while an antagonist blocks the neurotransmitter to decrease it. Myelin is separate: it is insulation that speeds the signal along the neuron.
A drug binds to a receptor and prevents the neurotransmitter from binding there, with no effect of its own. What kind of drug is it, and what happens to the signal at that synapse?
Reviewed- A.An agonist; the signal increases
- B.An antagonist; the signal decreases
- C.An agonist; the signal decreases
- D.An antagonist; the signal increases
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Answer: B. An antagonist; the signal decreases
- Step 1: Read the action: The drug blocks the neurotransmitter and does nothing itself. Blocking is the antagonist's job.
- Step 2: Predict the signal: If the real neurotransmitter cannot bind, the signal at that synapse goes down.
Why it's right: A drug that blocks the neurotransmitter is an antagonist, and blocking the messenger decreases the signal at that synapse.
- A: An agonist mimics the neurotransmitter and increases the signal; this drug blocks it.
- C: An agonist increases the signal, so 'agonist; decreases' is contradictory.
- D: An antagonist blocks, so it decreases the signal, not increases it.
Aligned to HBS 2.1: agonist vs antagonist at the synapse · reading level ~grade 9
- A nurse explaining an antihistamine notes it is an antagonist: it blocks the histamine signal that causes itching and swelling.
Fill these in as you work through the lesson.
- Synapse (the gap between two neurons):
- Neurotransmitter (the chemical messenger that crosses the gap):
- Agonist (does it boost or block?):
- Antagonist (does it boost or block?):
- Myelin (insulation that does what to speed?):
At a synapse, an boosts or mimics the neurotransmitter so the signal goes UP, while an blocks it so the signal goes DOWN; meanwhile speeds the signal along the neuron.
- A drug binds the receptor and triggers the same effect as the natural neurotransmitter. Is it an agonist or an antagonist?
- A drug sits on the receptor and prevents the neurotransmitter from binding. What happens to the signal?
- Why would damage to the myelin around a neuron slow down signaling?
A medicine blocks a receptor so the body's own neurotransmitter cannot bind there. Decide whether the medicine is an agonist or an antagonist, and say whether the signal at that synapse goes up or down.