Questions: Which of the following is true of all the sensory pathways? They all have third-order neurons. They all enter through dorsal roots. Axons in each pathway decussate. They all synapse in the cerebellum. They all synapse in the thalamus.

The answer is: Axons in each pathway decussate.

Explanation for each option:

• They all have third-order neurons. This is incorrect. Not all sensory pathways have third-order neurons. For example, some pathways may involve only first and second-order neurons, especially those that do not reach the cerebral cortex.

• They all enter through dorsal roots. This is incorrect. While many sensory pathways do enter the spinal cord through the dorsal roots, not all sensory pathways do so. For example, cranial nerves can carry sensory information directly to the brain without entering through the dorsal roots.

• Axons in each pathway decussate. This is correct. Decussation, or crossing over to the opposite side, is a common feature of many sensory pathways, allowing the brain to process information from the opposite side of the body.

• They all synapse in the cerebellum. This is incorrect. While some sensory pathways, particularly those involved in proprioception and balance, do synapse in the cerebellum, not all sensory pathways do so.

• They all synapse in the thalamus. This is incorrect. Although many sensory pathways do synapse in the thalamus before reaching the cerebral cortex, not all sensory pathways involve the thalamus. For example, olfactory pathways bypass the thalamus.

In summary, the characteristic that is true of all sensory pathways is that axons in each pathway decussate.