Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

16. The Endocrine System

Introduction to the Endocrine System

Anatomy & Physiology

16. The Endocrine System

Introduction to the Endocrine System

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2:15 minutes

Problem 12

Textbook Question

Describe the chemical nature of hormones.

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Hormones are chemical messengers secreted by endocrine glands that regulate physiological processes in the body. They are classified based on their chemical structure into three main types: peptide hormones, steroid hormones, and amine hormones.

Peptide hormones are composed of chains of amino acids. Examples include insulin and glucagon. These hormones are water-soluble and typically bind to receptors on the surface of target cells.

Steroid hormones are derived from cholesterol and include hormones like cortisol, testosterone, and estrogen. These hormones are lipid-soluble, allowing them to pass through cell membranes and bind to intracellular receptors.

Amine hormones are derived from amino acids, specifically tyrosine or tryptophan. Examples include epinephrine, norepinephrine, and thyroid hormones. Their solubility varies; catecholamines like epinephrine are water-soluble, while thyroid hormones are lipid-soluble.

The chemical nature of hormones determines their mode of transport in the bloodstream (bound to carrier proteins or free) and their mechanism of action (surface receptor binding or intracellular receptor binding). Understanding these properties is essential for studying their physiological effects.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hormonal Classification

Hormones can be classified into three main categories: peptides, steroids, and amines. Peptide hormones are made of amino acids and are water-soluble, while steroid hormones are derived from cholesterol and are lipid-soluble. Amines are derived from single amino acids and can be either water or lipid-soluble, depending on their structure. This classification is essential for understanding how hormones interact with target cells.

Mechanism of Action

Hormones exert their effects by binding to specific receptors on target cells, which can be located on the cell surface or within the cell. Water-soluble hormones typically bind to surface receptors, triggering a cascade of intracellular signaling pathways, while lipid-soluble hormones can pass through the cell membrane and directly influence gene expression. This mechanism is crucial for understanding how hormones regulate various physiological processes.

Feedback Mechanisms

Hormonal regulation often involves feedback mechanisms, primarily negative feedback, which helps maintain homeostasis. In negative feedback, the release of a hormone is inhibited by the effects it produces, ensuring that hormone levels remain within a specific range. This concept is vital for understanding how the endocrine system maintains balance in bodily functions, such as metabolism, growth, and stress response.

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Related Practice

Textbook Question

A cell's hormonal sensitivities are determined by the:

(a) Chemical nature of the hormone

(b) Quantity of circulating hormone

(d) Presence or absence of appropriate receptors

(e) Thickness of its plasma membrane

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Textbook Question

More than one choice may apply. In the hormone-signaling pathway represented in the figure,_________ is the first messenger, and _______is the second messenger that will signal a change in cell activity.

Explain what mechanism of hormone action is occurring in this image. How does it work? Give an example of a hormone that uses this mechanism.

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Textbook Question

What six hormones primarily affect growth?

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Textbook Question