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Questions and Answers
Which type of hormone acts primarily through intracellular receptors located in the cytoplasm or nucleus?
Which type of hormone acts primarily through intracellular receptors located in the cytoplasm or nucleus?
How do protein-bound hormones differ from free hormones in the blood?
How do protein-bound hormones differ from free hormones in the blood?
What happens to target cell receptors during chronic high levels of a hormone in the blood?
What happens to target cell receptors during chronic high levels of a hormone in the blood?
What is the correct sequence of events in the hormone signaling mechanism initiated by a hormone?
What is the correct sequence of events in the hormone signaling mechanism initiated by a hormone?
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Which of the following is NOT a characteristic of hormone receptors?
Which of the following is NOT a characteristic of hormone receptors?
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Which hormones primarily use the phospholipid membrane pathway for signaling?
Which hormones primarily use the phospholipid membrane pathway for signaling?
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What effect does chronic low hormone levels have on hormone receptors?
What effect does chronic low hormone levels have on hormone receptors?
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Why are steroid hormones effective at binding to their receptors?
Why are steroid hormones effective at binding to their receptors?
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What is the result of the hormone binding to its receptor in membrane pathways?
What is the result of the hormone binding to its receptor in membrane pathways?
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Which mechanism is described as rapid and transient?
Which mechanism is described as rapid and transient?
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What is the role of cAMP in the adenylate cyclase pathway?
What is the role of cAMP in the adenylate cyclase pathway?
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In the calcium-calmodulin pathway, what is the first step after hormone binding?
In the calcium-calmodulin pathway, what is the first step after hormone binding?
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Why is the intracellular receptor pathway considered slow?
Why is the intracellular receptor pathway considered slow?
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Which type of hormones primarily act through membrane receptor pathways?
Which type of hormones primarily act through membrane receptor pathways?
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What physiological action results from the phosphorylation of proteins in the adenylate cyclase pathway?
What physiological action results from the phosphorylation of proteins in the adenylate cyclase pathway?
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What is the main purpose of second messengers in hormone signaling pathways?
What is the main purpose of second messengers in hormone signaling pathways?
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What occurs after the hormone binds to its receptor in the membrane during the phospholipid membrane pathway?
What occurs after the hormone binds to its receptor in the membrane during the phospholipid membrane pathway?
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What is the role of inositol triphosphate (IP3) in the phospholipid membrane pathway?
What is the role of inositol triphosphate (IP3) in the phospholipid membrane pathway?
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Which molecule produced during the phospholipid membrane pathway activates protein kinase C?
Which molecule produced during the phospholipid membrane pathway activates protein kinase C?
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What are the final products of protein kinase C activity in the phospholipid membrane pathway?
What are the final products of protein kinase C activity in the phospholipid membrane pathway?
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What is the primary action of the active G protein in the phospholipid membrane pathway?
What is the primary action of the active G protein in the phospholipid membrane pathway?
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Which step involves the liberation of diacylglycerol during the phospholipid membrane pathway?
Which step involves the liberation of diacylglycerol during the phospholipid membrane pathway?
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How does calcium function in the phospholipid membrane pathway?
How does calcium function in the phospholipid membrane pathway?
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What is the initial event triggered by hormone binding in the phospholipid membrane pathway?
What is the initial event triggered by hormone binding in the phospholipid membrane pathway?
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Study Notes
Physiology and Anatomy II - Endocrine System
- Course instructor: Dr. Maha Gamal
- Email: [email protected]
Grade Distribution
- Final exam: 40%
- Midterm exam: 30%
- Quizzes: 20%
- Student activities (class work & essay): 10%
Competency Objectives
- Demonstrate the anatomy of the endocrine system.
- Define endocrine glands and hormones.
- Describe the chemical nature of hormones.
- Compare the two forms of hormones in blood.
- Define hormone receptors, describing their site, characteristics, and regulation.
- Explain hormone action mechanisms (signal transduction pathways).
- Demonstrate the different regulatory mechanisms of hormone action.
Anatomy of the Endocrine System
- Pituitary gland: A small gland (1/2 g) located in a fossa at the base of the skull, below the brain.
- Thyroid gland: Butterfly-shaped gland in front of the lower larynx and upper trachea, connected by an isthmus, moves with larynx movement.
- Parathyroid glands: Four small yellowish glands embedded behind the thyroid.
- Suprarenal (Adrenal) glands: Two triangular glands on top of the kidneys, with cortex and medulla.
- Pancreas: A mixed endocrine and exocrine gland, located transversely on the posterior abdominal wall, extending from the duodenum to the spleen.
- Gonads: Two testes in males, two ovaries in females.
The Endocrine Glands
- Ductless glands secreting hormones into interstitial spaces, absorbed into the bloodstream for distribution to target tissues.
Hormones
- Definition: Specific chemical substances secreted in small amounts by endocrine glands, affecting nearby or distant target cells; chemical messengers.
- Chemical Nature: Classified into protein/polypeptide (hypothalamic, pituitary, pancreatic, parathyroid), steroid (adrenocortical, gonadal, active vitamin D), and tyrosine derivatives (thyroid, adrenal medullary).
Forms in the Blood
- Free: Not bound to proteins, directly bind to receptors, small size, filtered in urine.
- Protein-bound: Carried by plasma proteins, inactive, large size, not filtered in urine; storage form.
Hormone Receptors
- Located on cell membranes, cytoplasm, or nucleus.
- Characterized by being proteins, specific, and dynamic (number changes based on physiological conditions).
-
Regulation: Occurs through:
- Downregulation: Chronic high hormone levels lead to fewer receptor sites.
- Upregulation: Chronic low levels result in more receptor sites.
Mechanisms of Hormone Action (Signal Transduction Pathways)
1. Pathways Initiated by Intracellular Receptors
- Mechanism: For steroid and thyroid hormones (lipid soluble) that pass through the cell membrane.
- Steps:
- Hormone diffuses through the membrane.
- Binds to intracellular receptor, activating it.
- H-R complex binds to DNA influencing transcription.
- mRNA is produced directing protein synthesis producing physiologic effects.
- Slow process due to protein synthesis.
2. Pathways Initiated From Cell Membrane Receptors
- Mechanism: Used by peptide and protein hormones.
- Types:
- A. Adenylate cyclase pathway: Activation of G proteins, cAMP production, activating protein kinase A, phosphorylating enzymes, and altering cell activity.
- B. Calcium-calmodulin pathway: Activation of G proteins, releasing intracellular calcium, calcium-calmodulin binding, initiating protein kinase activation and physiologically important effects.
- C. Membrane phospholipid pathway: Activates G protein, activating phospholipase C, releasing diacylglycerol and IP3, increasing intracellular calcium, activating protein kinase C, and producing physiologic actions.
Mechanism of Action of Different Hormones
- Tables displaying hormones and mechanisms (e.g., cAMP, IP3, steroid hormone).
Regulation of Hormone Secretion
- Nervous control: External or internal stimuli affect hormone secretion, either directly or via hypothalamic releasing/inhibiting hormones.
-
Feedback control:
- Negative feedback: Hormone levels influence gland function, influencing increase or decrease in secretion (most common).
- Positive feedback: High hormone levels stimulate further production to maintain a high level. (less common)
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Description
This quiz covers the anatomy and physiology of the endocrine system as outlined in the course. You'll be tested on endocrine glands, hormones, and their mechanisms of action. Prepare to demonstrate your understanding of how hormones regulate various bodily functions.
