Question

q8. the tips of neuronal axons communicate with other nerve cells by releasing small molecules called neurotransmitters. these neurotransmitters need to cross a very tiny pocket of fluid to reach the next neuron; the distance is about 0.001 times the length of the smallest axon in this lab. could this happen through diffusion?

yes, because the neurotransmitters will want to reach their target neuron on the other side of the fluid pocket.

yes, because the neurotransmitters are at high concentration near the diffusing axon and at low concentration next to the receiving neuron.

no, because diffusing any distance takes a very long time, and neural communication has to happen rapidly.

no, because diffusion does not work within very small spaces, only in large areas where there is room for the molecules to move.

Explanation:

To determine if neurotransmitters can cross the fluid pocket via diffusion, we analyze each option:

• First option: Incorrect. Diffusion is passive (molecules don’t “want” to move; they move due to concentration gradients).
• Second option: Correct. Diffusion occurs from high to low concentration. Neurotransmitters are released (high concentration near the axon) and need to reach the receiving neuron (low concentration), so diffusion is feasible over a very short distance (0.001 times the smallest axon length).
• Third option: Incorrect. Over extremely short distances (like a tiny fluid pocket), diffusion is rapid enough for neural communication.
• Fourth option: Incorrect. Diffusion works in small spaces (e.g., the synaptic cleft, which is tiny) as long as there’s a concentration gradient.

Answer:

Yes, because the neurotransmitters are at high concentration near the diffusing axon and at low concentration next to the receiving neuron.