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Chapter 42 – Endocrine System

Chapter 42 – Endocrine System. Chemical Signals. Categories of Signals Chemical signals are used: (1) between individuals , (2) between body parts , & (3) between cells. The Action of Hormones. The Action of Hormones

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Chapter 42 – Endocrine System

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  1. Chapter 42 – Endocrine System

  2. Chemical Signals • Categories of Signals • Chemical signals are used: (1)between individuals, (2)between body parts, & (3)between cells

  3. The Action of Hormones • The Action of Hormones • A hormone does not seek out a target organ; the organ is awaiting the arrival of the hormone. • Steroid hormones • Peptide hormones

  4. Target Cell Concept

  5. Action of Hormones • Chemical signals produced by one cell that regulate the metabolism of other cells • Steroid Hormones -Can cross cell membranes • Peptide Hormones • Most bind to receptor in plasma membrane • First Messenger • Causes internal release of cAMP • Second Messenger

  6. Steroid Hormone See ISP 45.2 Hormone-receptor complex binds to DNA resulting in activation of genes that produce enzymes Inside a nucleus, hormones such as estrogen & progesterone bind to a specific receptor Steroid hormones are lipids and cross cell membranes freely

  7. They are lipids that cross cell membranes freely have the same complex of four carbon rings but have different side chains

  8. Peptide Hormone cAMP sets an enzyme cascade in motion Activated enzymes can be used repeatedly, resulting in a thousand-fold response Cyclic AMP (cAMP) is made from ATP; it has one phosphate group attached to adenosine at two locations Peptide hormones are the first messenger; cAMP and calcium are often the 2nd messenger Peptide hormones never enter a cell so theybind to a receptor protein in plasma membrane. Peptide Hormones.ram

  9. Human Endocrine System • Endocrine Glands • Endocrine glands- ductless glands in contrast to exocrine glands with ducts. • Endocrine systemconsists of endocrine glandsthat coordinate body activities throughhormones. • Their hormones are secreted directly into bloodstream.

  10. Human Endocrine System • Principal human endocrine glands: • Hypothalamus, pineal, and pituitary glands brain. • Thyroid and parathyroid glands neck. • Thymusthoracic cavity • Adrenals & pancreasabdomen area • Ovariespelvic cavity • testesscrotum

  11. Homeostasis • Endocrine system is especially involved with homeostasis. • Effect of hormones is controlled in 2 ways: • Negative Feedback • Stops release of hormone • Antagonistic hormones • Hormones have opposing (or opposite) effect

  12. Homeostasis • Negative feedback (ex.) • Pancreas produces insulin when blood glucose rises; this causes liver to store glucose. • When glucose is stored, level goes down and pancreas stops insulin production. • Antagonistic hormones (ex.) • Effect of insulin is offset by glucagon • Thyroidlowers blood calcium level; parathyroidsraise blood calcium level.

  13. Hypothalamus • regulates the internal environment through the autonomic system. • It controls heartbeat, temperature, water balance, as well as glandular secretions of pituitary gland. • Pituitary Gland • Connected to hypothalamus • Lies just below the hypothalamus. • Two portions: posterior & anterior pituitary

  14. This portion of pituitary gland is connected to hypothalamus by a stalk-like structure. • It contains portions of neurosecretory cellsthat originate in hypothalamus & respondto neurotransmitters to produce hormones. Posterior Pituitary

  15. Hypothalamus produces antidiuretic hormone (ADH or vasopressin) and oxytocin,which pass through axon endings in posterior pituitary and are stored until released. Posterior Pituitary

  16. Posterior Pituitary • Antidiuretic hormone (ADH) promotes reabsorption of water from collecting ducts in kidneys. • Nerve cells in the hypothalamus determine when blood is too concentrated; ADH isreleased and kidneys respond by reabsorbing water. • As blood becomes dilute, ADH is no longer released; this is a case of negativefeedback.

  17. Posterior Pituitary • Oxytocinis also made in hypothalamus & stored in posterior pituitary. • Oxytocin • stimulates uterine muscle contraction • stimulates release of milk from mammary glands • This positive feedback increases intensity; positive feedback does not maintain homeostasis.

  18. Anterior Pituitary • Stimulation by hypothalamus controls release of anterior pituitary hormones; • Hypothalamus produces: • hypothalamic-releasing hormones • hypothalamic-inhibitinghormones • These pass to anterior pituitary by portal systemof two capillary beds &one vein.

  19. Negative Feedback Thyroid-inhibiting hormones (TIH) Produced in & released from hypothalamus act on cells in anterior pituitary to inhibit production & secretion Thyroid Stimulating Hormone (TSH) Thyroid-releasing hormones (TRH) Produced & released from hypothalamus act on cells in anterior pituitary to produce Thyroid Stimulating Hormone (TSH).

  20. Anterior Pituitary • AP produces 6 different hormones (each by a distinct cell type) • 3 affect other glands (Tropic Hormones) • TSH; ACTH; Gonadotropic hormones (FSH & LH) • 3 directly effects on the body • PRL; MSH; GH

  21. Tropic Hormones affect other Glands (ACTH) - stimulates the adrenal cortex to release cortisol Gonadotropic hormones (FSH &LH) act on gonads (ovaries & testes) - secrete sex hormones Thyroid-stimulating hormone (TSH) - stimulates thyroid to produce & secrete thyroxin

  22. Hormones that directly affect the body Prolactin (PRL) is produced only after childbirth. Causes mammary glands to produce milk. Plays a role in carbohydrate and fat metabolism Growth hormone (GH) promotes skeletal & muscular growth

  23. Kosen visited the university in May 2010 for treatment for a disorder called acromegaly, which is usually caused by a tumor in the pituitary gland. Measuring at 8-feet-3 inches, 29-year-old Sultan Kosen of Turkey is listed in the 2011 Guinness World Records at the tallest living man. Figure 42.6

  24. Thyroid Gland • Thyroid glandis in neck and attached to trachea just below larynx. • Thyroxine (T4) -4 iodine atoms • Triiodothyronine (T3) - 3 iodine atoms • Thyroid hormones increase metabolic rate; there is no one target organ, all organs respond • Thyroid gland also produces calcitonin • Calcitoninlowers calcium level in blood and increases deposit in bone by reducing osteoclasts. • Low calcium levels stimulaterelease of parathyroid hormone (PTH)

  25. Video: Hypothalamus, pituitary,thyroid Video: Parathyroid glands

  26. Parathyroid Glands • 4parathyroid glandsare embedded in posterior surface of thyroid gland. • Produce parathyroid hormone(PTH) • PTH - Ca2+ level in blood increases & phosphate level decreases. • PTH stimulates the absorptionof Ca2+ by: • activating vitamin D – absorb Ca2+ at intestines • the retention of Ca2+ (andexcretion of phosphate) by the kidneys • demineralization of bone by promoting activityof osteoclasts

  27. Motor neurons can be divided into 2 groups • Somatic Nervous System • Autonomic Nervous System • 2 Divisions of the ANS • Sympathetic Nervous System • Parasympathetic Nervous System

  28. Autonomic Nervous System • Sympathetic Division- • “FIGHT or FLIGHT”response. • Sympathetic system is especially important during emergency situations. • Neurotransmitter released is mainly norepinephrine, (similar to epinephrine -adrenaline- used as a heart stimulant)

  29. Autonomic Nervous System • Parasympathetic Division • REST & DIGEST • System is “housekeeper system”; it promotesinternal responses resulting in a relaxed state. • Parasympathetic system causes eye pupil to constrict, promotes digestion, and retards heartbeat. • Neurotransmitter released is acetylcholine

  30. Adrenal Glands • Two adrenal glandssit atop each kidney. • Each gland consists of two parts: • adrenal cortex (outer) • adrenal medulla (inner) • Hypothalamus - control over both portions • Medulla - Nerve impulses travel via sympathetic nerve fibers • Cortex - Hypothalamus uses ACTH-releasing hormone to control anterior pituitary’s secretion ofACTH

  31. Figure 42.11

  32. Adrenal Medulla • Epinephrine& norepinephrine • Both hormones bring about body changes corresponding to Emergency(Fight or Flight). • Blood glucose level rises and metabolic rate increases. • Bronchioles dilate and breathing rate increases. • Blood vessels to digestive tract and skin constrict; those to skeletal muscles dilate. • Cardiac muscle contracts more forcefully and heart rate increases

  33. Figure 42.11

  34. Adrenal Cortex • Adrenal cortex hormones provide a sustained response to stress. • Adrenal cortex secretes two types of hormones: • Glucocorticoids • help regulate blood glucose levels • Mineralocorticoids • regulate levels of minerals in blood • It also secretes a small amount of both male & female sex hormones in both sexes

  35. Figure 42.11

  36. Glucocorticoids • Cortisol is a biologically significant glucocorticoid • Promotes breakdown of muscle protein to amino acids taken up by liver fromblood. • Breaks down fatty acids rather than carbohydrates; cortisol raises blood glucoselevels. • Counteracts the inflammatory response; it helps medicate arthritis and bursitis

  37. RAAS Renin- angotensin-aldosterone system works in 2 ways: Angiotensin II constricts arterioles Aldosterone cause kidney to absorb Na+

  38. Mineralocorticoid secretion is controlled by renin-angiotensin-aldosterone system. (RAAS) • enzyme renin converts plasma protein angiotensinogen to angiotensin I; this becomes angiotensin II by a converting enzyme in lungs. • Angiotensin I constricts arterioles directly; aldosterone causes kidneys to absorb Na+ When blood sodium rises, water is reabsorbed as hypothalamus secretes ADH; blood pressure increases • Angiotensin II stimulates adrenal cortex to release aldosterone. • Low blood vol. & Na+ levels - kidneys secrete renin

  39. Pancreas • Pancreas lies transverse in abdomen between kidneys and near duodenum. • Composed of two types of tissue. • Exocrine tissue - produces & secretes digestive juicesinto sm. intestine thruducts • Endocrine tissues • pancreatic islets(isletsof Langerhans) • produce insulinandglucagon

  40. pancreas & insulin.ram

  41. Pancreas • All body cells utilize glucose; therefore, its level must be closely regulated. • Beta cells secrete Insulinis secreted when blood glucose level is high after eating • Alpha cells secrete Glucagonis secreted between meals in response to low blood glucose level.

  42. Diabetes Mellitus • Diabetes mellitusis a common disease where body cells do not take up or metabolize sugar. • Liver is not storing glucose as glycogen & cells are not utilizing glucose for energy. • Type I (insulin-dependent) diabetes - pancreas does not produce insulin • type II (noninsulin-dependent) diabetes - usually occurs in obese & inactive individuals of any age. Cells do not respond to insulin

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