Anatomy & Physiology

Anatomy & Physiology Study Guide • Specialized muscle cells in the heart make natriuretic peptides (ANP and BNP) when blood volume is excessive. Their actions oppose those of angiotensin II. • The thymus creates several hormones, known as thymosins, which play a part in developing and maintaining standard immune defenses. • The interstitial cells of the testes make androgens. Testosterone is the most vital sex hormone in males. • Adipose tissue secretes leptin (a feedback control for appetite). • In females, oocytes grow in follicles; follicle cells create estrogens, especially estradiol. After ovulation, the remaining follicle cells restructure into a corpus luteum. Those cells release a combination of estrogens and progestins, especially progesterone. Hormones interact to produce coordinated physiological responses: • Endocrine system hormones often interact, producing antagonistic (opposing) effects; synergistic (additive) effects; permissive effects, in which one hormone is necessary for another to produce its effect; or integrative effects, in which hormones produce different but complementary results. • Normal growth has to have the cooperation of several endocrine organs. Several hormones are especially important: GH, thyroid hormones, insulin, PTH, calcitriol, and reproductive hormones. • Any condition that is a threat to homeostasis is a stressor. Our bodies respond to various stress-causing factors through the general adaptation syndrome (GAS), also called the stress response. • The GAS can be categorized into three phases: the alarm phase (an immediate, “fight or flight” response, under the direction of the sympathetic division of the ANS); the resistance phase, dominated by glucocorticoids; and the exhaustion phase, the eventual breakdown of homeostatic regulation and failure of one or more organ systems. • Many hormones affect the CNS; changes in the normal mixture of hormones can significantly alter intellectual capabilities, memory, learning, and emotional states. • The endocrine system undergoes few functional alterations with advanced age. The primary changes include a decline in the concentration of growth hormone and reproductive hormones. Extensive integration occurs between the endocrine system and other body systems: • The endocrine system provides long-term regulation and homeostatic adjustments that affect many body systems.

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