Acth

Cortisol inhibits CRH and ACTH

Bloodstream

Cortisol inhibits CRH and ACTH

Cortisol affects various target cells

Bloodstream

ACTH stimulates the adrenal cortex to release cortisol

ACTH stimulates the adrenal cortex to release cortisol

Cortisol

Cortisol affects various target cells

Stimulates glucose formation

Inhibits protein synthesis

Stimulates glucose formation

Cortisol

Inhibits protein synthesis

Promotes fatty acid release

Figure

Negative feedback regulates cortisol secretion, similar to the regulation of thyroid hormone secretion (see fig. 13.14).

into female hormones (estrogen) by the skin, liver, and adipose tissues. These hormones may supplement the supply of sex hormones from the gonads and stimulate early development of the reproductive organs. Also, adrenal androgens may play a role in controlling the female sex drive. Table 13.10 summarizes the actions of the cortical hormones. Clinical Application 13.3 discusses some of the effects of a malfunctioning adrenal gland on health.

Name the important hormones of the adrenal cortex.

What is the function of aldosterone?

What does cortisol do?

How are blood concentrations of aldosterone and cortisol regulated?

Pancreas

The pancreas (pan'kre-as) contains two major types of secretory tissues. This organization of cell types reflects its dual function as an exocrine gland that secretes digestive juice through a duct and an endocrine gland that releases hormones into body fluids.

Structure of the Gland

The pancreas is an elongated, somewhat flattened organ that is posterior to the stomach and behind the parietal peritoneum (fig. 13.32). It is attached to the first section of the small intestine (duodenum) by a duct, which transports its digestive juice into the intestine. The digestive functions of the pancreas are discussed in chapter 17 (p. 707).

The endocrine portion of the pancreas consists of cells grouped around blood vessels. These groups, called islets of Langerhans, include three distinct types of hormone-secreting cells—alpha cells, which secrete glucagon; beta cells, which secrete insulin; and delta cells, which secrete somatostatin (fig. 13.33).

Hormones of the Islets of Langerhans

Glucagon is a protein that stimulates the liver to break down glycogen into glucose (glycogenolysis) and to convert noncarbohydrates, such as amino acids, into glucose

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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