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Consider these lines: "The action potential is an all-or-none phenomenon. In simple terms, this means that an incoming signal from another neuron is either sufficient or insufficient to reach the threshold of excitation. Think of it like sending an email or a text message. You can think about sending it all you want, but the message is not sent until you hit the send button. Furthermore, once you send the message, there is no stopping it." What is the purpose of the email comparison in the quoted lines?
ATo show that neurons communicate by electronic mail inside the brain
BTo illustrate that a neuron either fires fully or not at all, with no recall
CTo argue that modern technology has changed how neurons behave
DTo explain why some messages between neurons get lost in transit
Answer & Solution
Correct answer: B. To illustrate that a neuron either fires fully or not at all, with no recall
1. The quoted lines first state the principle: a signal either reaches the threshold or it does not.
2. The email image then maps both halves of that principle onto a familiar act.
3. Nothing happens until the send button is pressed, which mirrors the threshold: below it, no firing at all.
4. Once sent, the message cannot be stopped, which mirrors the fact that a started action potential cannot be turned off.
5. So the comparison illustrates full firing or none, with no recall, which is option B.
6. Option A takes the analogy literally, as if email were the actual mechanism of neurons.
7. Option C treats an illustration as a causal claim about technology changing biology.
8. Option D invents lost messages, while the analogy is about delivery being certain once triggered.
_Source: OpenStax Psychology 1e (CC BY 4.0), Ch 3 "Biopsychology", section 3.2 Cells of the Nervous System_
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