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Questions and Answers
Which type of hormone is able to pass through the lipid membrane barrier of target cells?
What is the function of protein kinase A (PKA) in the cell signaling pathway?
Which of the following hormones is NOT a type of steroid hormone?
What is the function of plasma proteins in the transportation of hydrophobic steroid hormones?
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What is the result of epinephrine binding to receptors on the surface of liver cells?
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What is the common characteristic of hydrophilic hormones?
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What is the effect of activated receptors in the signaling cascade of hydrophilic hormones?
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Which of the following hormones is an example of a hydrophilic peptide hormone?
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What is the primary function of a tropic hormone?
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What is the mechanism by which hormones are transferred to target cells?
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What is the term for the process by which hormones regulate or direct a particular function in target cells?
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Which of the following hormones is an example of a non-tropic hormone?
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What is the term for the chemical messengers that can be either hormones or neurotransmitters, depending on their source and mode of delivery?
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What is the primary function of the endocrine system?
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How do hormones fall into distinct classes, according to their biochemical structure?
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What is the term for the hormone that stimulates the release of TSH from the anterior pituitary?
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What is the primary mechanism by which hydrophobic hormones regulate gene expression in target cells?
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What is the term for the effect of hormones on cells of the organ from which they were released?
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What is the primary function of the endocrine system in maintaining homeostasis?
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Which of the following is an example of a hormone that exerts an autocrine effect?
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What is the primary function of the hypothalamus in the endocrine system?
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Which of the following is a characteristic of hormones that are released into the bloodstream from endocrine glands?
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Study Notes
Endocrine System
- The endocrine system coordinates functioning between different organs through hormones released into the bloodstream from specific types of cells within endocrine (ductless) glands.
Endocrine Glands
- Endocrine glands secrete hormones into the blood, which are then transferred to all other cells of the body.
- Hormones travel in the blood to distant target cells, where they regulate or direct a particular function.
Hormones
- Hormones can be either tropic or non-tropic.
- Tropic hormones regulate hormone secretion by another endocrine gland (e.g., Thyrotropin-releasing hormone (TRH) stimulates the release of TSH from the anterior pituitary).
- Non-tropic hormones exert their effects on non-endocrine target tissue (e.g., thyroid hormone increases oxygen consumption and metabolic activity of almost all cells).
Classification of Hormones
- Hormones can be classified into three distinct classes based on their biochemical structure:
- Peptides (e.g., specific amino acids arranged in a chain of varying length; hydrophilic)
- Amines (e.g., derived from the amino acid, tyrosine)
- Steroids (e.g., neutral lipids derived from cholesterol; hydrophobic)
Transport of Hormones
- Hydrophilic peptide hormones are transported simply dissolved in the plasma.
- Hydrophobic steroid hormones circulate in the blood reversibly bound to plasma proteins.
Mechanism of Hormone Action
- Hydrophilic hormones bind to specific receptors located on the outer plasma membrane surface of target cells.
- Hydrophobic hormones easily pass through the surface membrane to bind with specific receptors located inside the target cell.
- Activated receptors initiate a signaling cascade leading to regulation of enzyme activity or affect ion channels.
Examples of Hormone Action
- Epinephrine (adrenalin) binding in liver stimulates synthesis of second messenger cAMP, leading to glucose release.
- Corticosteroids, vitamin D, and thyroxine function by binding and activating specific receptors inside target cells, regulating gene expression.
Endocrine System Functions
- Regulates metabolism and water and electrolyte balance to maintain a constant internal environment (homeostasis).
- Induces adaptive changes to help the body cope with stressful situations.
- Promotes smooth, sequential growth and development.
- Regulates red blood cell production.
- Controls and integrates both circulation and digestion and absorption of food (along with the autonomic nervous system).
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Description
Learn about the endocrine system, including how ductless glands secrete hormones into the blood, and how hormones regulate specific functions in target cells. Review signal transduction cascades to get the most out of this lecture!
