Figure 1011

Pathways by which the nervous system influences hormone secretion. (a) Certain neurons in the hypothalamus, some of which terminate in the posterior pituitary, secrete hormones. The secretion of hypothalamic hormones from the posterior pituitary and the effects of other hypothalamic hormones on the anterior pituitary are described later in this chapter. (b) The autonomic nervous system controls hormone secretion by the adrenal medulla and many other endocrine glands.

Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition

Principles of Hormonal Control Systems CHAPTER TEN

Principles of Hormonal Control Systems CHAPTER TEN

Thus far, our discussion of neural control of hormone release has been limited to the role of the autonomic nervous system (Figure 10-11b). However, one large group of hormones—those secreted by the hypothalamus and its extension, the posterior pituitary—are under the direct control not of autonomic neurons but of neurons in the brain itself (Figure 10-11a). This category will be described in detail later in this chapter.

Control by Other Hormones

In many cases, the secretion of a particular hormone is directly controlled by the blood concentration of another hormone. As we shall see, there are often complex sequences in which the only function of the first few hormones in the sequence is to stimulate the secretion of the next one. A hormone that stimulates the secretion of another hormone is often referred to as a tropic hormone. The tropic hormones usually stimulate not only secretion but the growth of the stimulated gland as well.

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Essentials of Human Physiology

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