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Biology LibreTexts

37.1A: Hormone Functions

  • Page ID
    13968
  • The endocrine system plays a role in growth, metabolism, and other processes by releasing hormones into the blood.

    Learning Objectives

    • Evaluate hormones and their purpose in the body

    Key Points

    • Hormones serve as chemical messengers in the body and help maintain homeostasis.
    • Hormones are released into bodily fluids, like blood, which carry them to target cells.
    • Target cells respond to a hormone when they express a specific receptor for that hormone.
    • Hormones also play a role in the regulation of cell death, the immune system, reproductive development, mood swings, and hunger cravings.
    • In the adrenal gland, epinephrine and norepinephrine regulate responses to stress; in the thyroid gland, thyroid hormones regulates metabolic rates.

    Key Terms

    • target cell: any cell having a specific receptor for a hormone
    • hormone: any substance produced by one tissue and conveyed by the bloodstream to another to affect physiological activity
    • endocrine system: a control system of ductless glands that secrete hormones which circulate via the bloodstream to affect cells within specific organs

    The Endocrine System: Hormones

    An animal’s endocrine system controls body processes through the production, secretion, and regulation of hormones. Hormones serve as chemical “messengers” that function in cellular and organ activity to maintain the body’s homeostasis. Maintaining homeostasis within the body requires the coordination of many different systems and organs. Communication between neighboring cells and between cells and tissues in distant parts of the body occurs through the release of hormones into body fluids (usually blood), which carry them to their target cells. Target cells, those having a receptor for a signal, respond to a hormone when they express a specific receptor for that hormone. Cellular recipients of a particular hormonal signal may be one of several cell types that reside within a number of different tissues, as is the case for insulin, which triggers a diverse range of systemic physiological effects. Different tissue types may also respond differently to the same hormonal signal.

    By releasing hormones, the endocrine system plays a role in growth, metabolism, and sexual development. Hormones also play a role in induction or suppression of cell death, activation or inhibition of the immune system, mood swings, and hunger cravings. In humans, common endocrine system diseases include thyroid disease and diabetes mellitus.

    Examples of endocrine glands include the adrenal glands, which produce hormones, such as epinephrine and norepinephrine that regulate responses to stress, and the thyroid gland, which produces thyroid hormones that regulate metabolic rates. In organisms that undergo metamorphosis, the process is controlled by the endocrine system. The transformation from tadpole to frog, for example, is complex and nuanced to adapt to specific environments and ecological circumstances.

    image

    Hormones in metamorphosis: The process of amphibian metamorphosis, as seen in the tadpole-to-frog stages shown here, is driven by hormones.