Final answer:
The olfactory bulb is the reflex center involved in olfaction and is positioned posterior to the pituitary gland. It processes smell information and sends signals directly to the brain's areas responsible for memory and emotion.
Step-by-step explanation:
The reflex center involved in olfaction (the sense of smell) and located posterior to the pituitary gland is the olfactory bulb. The olfactory bulb is a key structure in processing the sense of smell, and unlike most other senses, olfactory information is not primarily relayed through the thalamus. Instead, the olfactory bulb sends signals directly to other parts of the brain, such as the olfactory cortex and the limbic system, including areas involved in memory and emotions like the hippocampus and the amygdala. This unique pathway allows for the intimate connection between smell and memory or emotional responses.