Question

1. the all - or - none principle of nerve action refers to the condition in which

a. a stimulus activates every nerve in the body or none of the nerves at all
b. all stimuli reaching nerve cells activate them; no stimulus goes unheeded
c. a stimulus depolarizes all the neurons in a nerve or no neurons at all
d. a stimulus activates a nerve cell to function to capacity or not to function at all
use the following information to answer question 20.
three possible synaptic control patterns (x, y, and z)
\active\ means transmitting impulses; \inactive\ not transmitting impulses.

1. if axons 1 and 2 were activated at the same time, the most likely interpretation of diagram z would be that

a. axon 2 would inhibit the effect of axon 1
b. axon 3 would increase the effect of axon 2
c. axon 3 would only be affected by axon 1
d. axon 1 would inhibit the effect of axon 2
hint: in order, analyze x, then y, and then z. put all your ideas together to assess the question about axon z.

Explanation:

1. For question 19: The all - or - none principle states that a nerve cell either fires at full strength (functions to capacity) when the threshold stimulus is reached or does not function at all if the stimulus is below the threshold. Option A is incorrect as it's not about all nerves in the body, just a single nerve cell. Option B is wrong because not all stimuli activate nerve cells; only those above the threshold do. Option C is inaccurate as it's about a single nerve cell's response, not all neurons in a nerve.
2. For question 20: In diagram Z, when Axon 1 and Axon 2 are active and Axon 3 is inactive. If Axon 1 and Axon 2 are activated simultaneously, Axon 2 likely inhibits the effect of Axon 1, preventing Axon 3 from becoming active. In option B, Axon 3 is inactive so it can't increase the effect of Axon 2. Option C is wrong since Axon 3 is not only affected by Axon 1 as Axon 2's state matters too. Option D is incorrect as it's Axon 2 that seems to be inhibiting, not Axon 1.

Answer:

1. D. a stimulus activates a nerve cell to function to capacity or not to function at all
2. A. Axon 2 would inhibit the effect of Axon 1