Final answer:
The posterior pituitary gland is a central nervous system organ that stores and releases hormones produced by the hypothalamus, while the area postrema is also associated with the brain.
Step-by-step explanation:
The posterior pituitary gland and the area postrema are organs associated with the central nervous system. The posterior pituitary is an extension of the hypothalamus and not a true gland since it does not produce hormones but stores and releases them. These hormones include oxytocin and anti-diuretic hormone (ADH), which are produced by the hypothalamus and sent down to the posterior pituitary for storage and later release into the bloodstream.
The posterior pituitary is part of the neurohypophysis (along with the infundibulum) and contains nerve fibers and neuroglial cells. It is significantly different in structure from the anterior pituitary, which is glandular in nature. This proximity to the brain implies that the posterior pituitary's primary role is to act as a conduit for the hypothalamic hormones to enter systemic circulation.