The hypothalamus is the part of the brain that monitors many aspects of the state of the body systems, integrating a large amount of information from many sensory pathways. The connection between the hypothalamus and the pituitary gland results from hormones released from the hypothalamic neurones. The hypothalamus has two different connections with the pituitary gland. The connection to the adenohypophysis (the anterior lobe) is via a special portal blood system, whereas the connection to the neurohypophysis (the posterior lobe) is directly via neurones.
The hypothalamus is located underneath the thalamus and consists of many nerve cells (hypothalamic nuclei). As its role would suggest, the hypothalamus has a vast array of interconnections to other parts of the brain, including the pituitary gland itself. The lowest part of the hypothalamus that connects to the pituitary gland is known as the median eminence.
The hypothalamic nuclei send their axons to the pituitary gland into two distinct areas:
The hypothalamic neurones release many different secretions, and many have now been identified as peptides. Many of these secretions act as hormones as they are released in close proximity to capillaries and then enter the bloodstream. This release is known as neurosecretion. The neurosecretory cells in the hypothalamic nuclei have a multitude of connections to other parts of the brain and are influenced by many external stimuli such as stress and emotion.