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Chapter 9: Endocrine System

Chapter 9: Endocrine System. Question to ponder…..and to know…. Which two organ systems are responsible for the regulation of the body’s activities?. Answer:. Nervous and Endocrine Systems. Comparison of Endocrine and Nervous. 1. The way in which they communicate with other cells :

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Chapter 9: Endocrine System

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  1. Chapter 9: Endocrine System

  2. Question to ponder…..and to know…. Which two organ systems are responsible for the regulation of the body’s activities?

  3. Answer: Nervous and Endocrine Systems

  4. Comparison of Endocrine and Nervous 1. The way in which they communicate with other cells: • Nervous system: Nerve impulses and neurotransmitters • Endocrine system’s communication: chemical messengers (hormones) that are released into the blood

  5. Comparison of Endocrine and Nervous 2. Rate of their control • Nervous System: its effects are fast and short-lived (millisec to secs) • Endocrine: its effects are slow but last longer (minutes, weeks, days) • Takes minutes or days to bring about its effects

  6. Comparison of Endocrine and Nervous 3. Types of Body Processes they Control • Nervous System: Short-term processes • Stimulation of Muscle contraction and Glands • Endocrine System: Long-term processes • Reproduction, Growth/Development, Metabolism, and Mobilization of body defenses.

  7. Endocrine gland vs. Exocrine gland • Exocrine gland • Have ducts that carry their secretory product to a surface (sweat, sebaceous) • Endocrine gland • Ductless glands that secrete hormones into the blood stream

  8. Hormone Overview • Hormones are produced by endocrine glands Definition of Hormone: Chemical substances secreted by cells into extracellular fluids, that regulate the metabolic activity of other cells in the body. • Blood transfers hormones to target sites

  9. The Chemistry of Hormones • Types of hormones • Most are: 1. Amino acid-based molecules (non-steroids) • Proteins • Peptides • Amines 2. Steroids – made from cholesterol

  10. Mechanisms of Hormone Action • Hormones affect only certain tissues or organs (target cells or organs) • Target cells must have specific protein receptors on their plasma membrane or in its interior so that the hormone can attach • Hormone binding influences the working of the cells

  11. Effects Caused by Hormones • When hormones bind, one or more of the following occur: • Changes in plasma membrane permeability or electrical state • Synthesis of proteins, such as enzymes • Activation or inactivation of enzymes • Stimulation of mitosis

  12. Homework • Read the section: Mechanisms of Hormone Action—pg.280-281. How do steroid and nonsteroid (amino acid based) hormones work?

  13. Steroid Hormone Action • Diffuse through the plasma membrane of target cells: lipid soluble • Enter the nucleus • Bind to a specific protein within the nucleus • Hormone-receptor complex binds to specific sites on the cell’s DNA • Activate genes that result in synthesis of new proteins(change the activity of the cell)

  14. Steroid Hormone Action PRESS TO PLAY STEROID HORMONE ANIMATION Figure 9.1a

  15. Nonsteroid (Amino acid based) Hormone Action • Hormone binds to a membrane receptor • Hormone does not enter the cell • Hormone- “1st messenger” • Sets off a series of reactions that activates an enzyme • Catalyzes a reaction that produces a second messenger molecule (like cAMP) • 2nd messenger oversees additional intracellular reactions to promote a specific response

  16. Amino Acid-based Hormone Action PRESS TO PLAY NONSTEROID HORMONE ANIMATION Figure 9.1b

  17. Control of Hormone Release • Hormone levels in the blood are maintained by negative feedback • A stimulus or low hormone levels in the blood triggers the release of more hormone • Hormone release stops once an appropriate level in the blood is reached

  18. Stimulation of Endocrine Glands • Hormonal:hormones stimulate end. glands • Humoral: specific concentrations of certain elements or ions in the blood stimulate end.glands • Neural: nervous system stimulates end.glands

  19. Hormonal Stimuli of Endocrine Glands • Endocrine glands are activated by other hormones • Most common stimulus • The pituitary gland secretes hormones that trigger the release of hormones from other endocrine glands Figure 9.2a

  20. Humoral Stimuli of Endocrine Glands • Changing blood levels of certain ions stimulate hormone release • The thyroid gland and parathyroid glands respond to blood calcium levels. Figure 9.2b

  21. Neural Stimuli of Endocrine Glands • Nerve impulses stimulate hormone release • Most are under control of the sympathetic nervous system • A sympathetic nerve stimulates the release of epinephrine from the adrenal medulla Figure 9.2c

  22. Location of Major Endocrine Organs Figure 9.3

  23. Pituitary Gland • Size of a grape • Hangs by a stalk from the hypothalamus • Protected by the sphenoid bone • Has two functional lobes • Anterior pituitary – glandular tissue • Posterior pituitary – nervous tissue

  24. Hormones of the Anterior Pituitary • Six anterior pituitary hormones • Two affect non-endocrine targets • Four stimulate other endocrine glands (tropic hormones) • Tropic hormone: Any hormone that stimulates other endocrine glands

  25. Anterior Pituitary • Characteristics of all anterior pituitary hormones • Proteins (or peptides) • Act through second-messenger systems • Regulated by hormonal stimuli, mostly negative feedback

  26. Hormones of the Anterior Pituitary Figure 9.4

  27. Growth Hormone (GH) • General metabolic hormone • Major effects are directed to growth of skeletal muscles and long bones • Causes amino acids to be built into proteins “anabolic” • Causes fats to be broken down for a source of energy “catabolic”

  28. Growth Hormone • Hyposecretion: • In Childhood: Pituitary Dwarfism • Body proportions are normal • Max height: 4 feet

  29. Hypersecretion: • In Childhood: Gigantism • Body proportions are normal • 8-9 feet tall

  30. Hypersecretion • Hypersecretion: After long bone growth • “Acromegaly”-Enlarged facial bones, hands, feet, thickening of soft tissues

  31. Functions of Other Anterior Pituitary Hormones • Prolactin (PRL) • Stimulates and maintains milk production following childbirth (mammary glands) • Function in males is unknown • Adrenocorticotropic hormone (ACTH) • Regulates endocrine activity of the adrenal cortex • Stimulates it to release glucocorticoids • Thyroid-stimulating hormone (TSH) • Stimulates endocrine activity of the thyroid gland

  32. Functions of Other Anterior Pituitary Hormones • Gonadotropic hormones • Regulate hormonal activity of the gonads • Follicle-stimulating hormone (FSH) • Stimulates follicle development in ovaries and development of ova • Stimulate follicles to produce estrogens • Stimulates sperm development in testes

  33. Functions of Other Anterior Pituitary Hormones • Luteinizing hormone (LH) females • Triggers ovulation: release of egg from ovary • Ruptured follicle (corpus luteum secretes estrogen/progesterone) • Helps to regulate the menstrual cycle • Stimulates testosterone production in males • Referred to as interstitial cell-stimulating hormone (ICSH)

  34. Hypothal.: growth releasing hormone • Growth inhibiting hormone • G: growth hormone • G: gonadotropic hormones(FSH, LH (ICSH) • P: prolactin • A: adrenocorticotropic hormone • T: thyroid stimulating hormone

  35. Pituitary - Hypothalamus Relationship • Hypothalamus has releasing and inhibiting hormones • Controls the release of the anterior pituitary hormones • These hormones travel through the blood to the anterior pituitary

  36. Pituitary - Hypothalamus Relationship • Hypothalamus extends axons from its neurons into the posterior pituitary • Two hormones are transported from neurosecretory cells to the posterior pituitary along these axons • The posterior pituitary is not strictly an endocrine gland, but does release hormones

  37. Hormones of the Posterior Pituitary • Oxytocin • Stimulates contractions of the uterus during labor, sexual intercourse, breast feeding. • Causes milk ejection “let down reflex” • Stop postpartum bleeding • Natural and synthetic drugs(Pitocin)- • Used to induce labor or speed it up • Stimulate let down reflex • Stop postpartum bleeding

  38. Hormones of the Posterior Pituitary • Antidiuretic hormone (ADH) • Also called “Vasopressin” • Diuresis (urine production) • Acts on the kidney to maintain water balance • Decreases formation of urine (so kidneys reabsorb water) • In large amounts, increases blood pressure by causing vasoconstriction • In large amounts, can inhibit urine production

  39. Hormones of the Posterior Pituitary Figure 9.5

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