The integration of endocrine and nervous systems results in regulation of the body's activities to adjust to shifting environmental and developmental conditions.

Let us start with hypothalamus and pituitary gland, which control much of the endocrine system. The hypothalamus plays an important role in integrating the vertebrate endocrine and nervous systems. This region of the lower brain receives information from nerves throughout the body and from other parts of the brain, then initiates endocrine signals appropriate to environmental conditions.

In many vertebrates, for example, the brain passes sensory information about seasonal changes and the availability of a mate to the hypothalamus by means of nerve signals; the hypothalamus then triggers the release of reproductive hormones required for breeding.

The hypothalamus contains two sets of neurosecretory cells whose hormonal secretions are stored in or regulate the activity of the pituitary gland, a lima bean–sized organ located at the base of the hypothalamus. No organ illustrates the close structural, functional and developmental relationship between the endocrine and nervous systems better than the pituitary gland.

It has discrete posterior and anterior parts, which are actually two fused glands that develop from separate regions of the embryo and perform very different functions. The posterior pituitary or neurohypophysis, is an extension of the hypothalamus that grows downward toward the mouth during embryonic development. It stores and secretes two hormones that are made by certain neurosecretory cells located in the hypothalamus; the long processes (axons) of these cells carry the hormones to the posterior pituitary.