Understanding Pathophysiology, 6e
Understanding Pathophysiology, 6e
6th Edition
ISBN: 9780323354097
Author: Sue E. Huether RN PhD, Kathryn L. McCance RN PhD
Publisher: Elsevier Science
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Chapter 18.1, Problem 1QC
Summary Introduction

To describe: Hormones.

Concept introduction: The endocrine system is the chemical signaling system that uses blood vessels as the information channels. The endocrine glands are ductless organs located within organ systems and contain groups of endocrine cells that secrete their hormones directly into their surroundings.

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Explanation of Solution

Endocrine cells or neurosecretory cells secrete hormones into the extracellular fluids, which are signaling molecules. The secreted hormones reach the target cells through the bloodstream. Hormones bind only to specific cells based on the corresponding receptors, and they act through chemical signals. Hormones maintain homeostasis and regulate growth, development, blood pressure, metabolism, and fluid concentration in the body.

Hormones are categorized into three major types such as polypeptides, steroids, and amines. Polypeptides and amine hormones are water-soluble hormones; however, steroid hormones are lipid soluble. Both differ in their receptor-binding nature; water-soluble hormones bind to cell surface receptors, and lipid-soluble hormones bind to both cell surface and nuclear receptors. Both peptide and steroid hormones travel through the bloodstream to reach different parts of the body.

Summary Introduction

To explain: The functional mechanism of hormones.

Concept introduction: The endocrine system is the chemical signaling system that uses blood vessels as the information channels. The endocrine glands are ductless organs located within organ systems and contain groups of endocrine cells that secrete their hormones directly into their surroundings.

Expert Solution
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Explanation of Solution

Mechanism of Hormone Action:

The hormone receptors of the target cell have mainly two functions:

(1) To recognize and bind specifically with high affinity to their particular hormones

(2) To initiate a signal to suitable intracellular effectors.

The sensitivity of the target cell to a hormone is related to the total number of receptors per cell or the affinity for the receptors to the hormone. The cells can increase or decrease their sensitivity to cells by regulating the number of receptors. Based upon this, it is classified into up-regulation and down-regulation.

If a cell increases the number of receptors, it is called as upregulation, and if the cell decreases the number of receptors, it is known as downregulation. Thus, the cell can adjust its sensitivity to the concentration of the signaling hormone.

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