Hypothalamus and Neurosecretion
Hypothalamus and
Neurosecretion
Because of the strategic importance of the pituitary in influencing most hormonal activities in the body, the pituitary was once called the “master gland.” This description is not appropriate, however, because the anterior pituitary hormones are regulated by a higher council, the neurosecretory centers of the hypothalamus. The hypothalamus is itself under ultimate control by the brain. The hypothalamus contains groups of neurosecretory cells, which are specialized nerve cells (Figure 36-5 and 36-6), that manufacture neurohormones, called releasing hormones or release-inhibiting hormones (or “factors”). These neurohormones travel down nerve fibers to their endings in the median eminence. Here they enter a capillary network to complete their journey to the anterior pituitary by way of the pituitary portal system. The hypothalamic hormones then stimulate or inhibit release of various anterior pituitary hormones. Several hypothalamic releasing and release-inhibiting hormones have been discovered, characterized chemically, and isolated in pure state (Table 36-1), although the identification and action of some of the hypothalamic hormones listed in Table 36-1 is still tentative.
Because of the strategic importance of the pituitary in influencing most hormonal activities in the body, the pituitary was once called the “master gland.” This description is not appropriate, however, because the anterior pituitary hormones are regulated by a higher council, the neurosecretory centers of the hypothalamus. The hypothalamus is itself under ultimate control by the brain. The hypothalamus contains groups of neurosecretory cells, which are specialized nerve cells (Figure 36-5 and 36-6), that manufacture neurohormones, called releasing hormones or release-inhibiting hormones (or “factors”). These neurohormones travel down nerve fibers to their endings in the median eminence. Here they enter a capillary network to complete their journey to the anterior pituitary by way of the pituitary portal system. The hypothalamic hormones then stimulate or inhibit release of various anterior pituitary hormones. Several hypothalamic releasing and release-inhibiting hormones have been discovered, characterized chemically, and isolated in pure state (Table 36-1), although the identification and action of some of the hypothalamic hormones listed in Table 36-1 is still tentative.
Support our developers
