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The Endocrine System

9. The Endocrine System. The Endocrine System. Second controlling system of the body Nervous system is the fast-control system Uses chemical messengers (hormones) that are released into the blood Hormones control several major processes Reproduction Growth and development

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The Endocrine System

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  1. 9 The Endocrine System

  2. The Endocrine System Second controlling system of the body Nervous system is the fast-control system Uses chemical messengers (hormones) that are released into the blood Hormones control several major processes Reproduction Growth and development Mobilization of body defenses Maintenance of much of homeostasis Regulation of metabolism

  3. Hormone Overview Hormones are produced by specialized cells Cells secrete hormones into extracellular fluids Blood transfers hormones to target sites These hormones regulate the activity of other cells

  4. The Chemistry of Hormones Hormones are classified chemically as Amino acid–based, which includes Proteins Peptides Amines Steroids—made from cholesterol Prostaglandins—made from highly active lipids

  5. Mechanisms of Hormone Action Hormones affect only certain tissues or organs (target cells or target organs) Target cells must have specific protein receptors Hormone-binding alters cellular activity

  6. Effects Caused by Hormones Changes in plasma membrane permeability or electrical state Synthesis of proteins, such as enzymes Activation or inactivation of enzymes Stimulation of mitosis Promotion of secretory activity

  7. The Chemistry of Hormones Two mechanisms in which hormones act Direct gene activation Second-messenger system

  8. Direct Gene Activation (Steroid Hormone Action) Diffuse through the plasma membrane of target cells Enter the nucleus Bind to a specific protein within the nucleus Bind to specific sites on the cell’s DNA Activate genes that result in synthesis of new proteins

  9. Nucleus Cytoplasm Steroidhormone Receptorprotein 1 2 3 Hormone-receptor complex 4 DNA mRNA 5 Newprotein Plasmamembraneof targetcell 6 (a) Steroid hormone action Figure 9.1a

  10. Nucleus Cytoplasm Steroidhormone 1 Figure 9.1a, step 1

  11. Nucleus Cytoplasm Steroidhormone Receptorprotein 1 2 Figure 9.1a, step 2

  12. Nucleus Cytoplasm Steroidhormone Receptorprotein 1 2 3 Hormone-receptor complex Figure 9.1a, step 3

  13. Nucleus Cytoplasm Steroidhormone Receptorprotein 1 2 3 Hormone-receptor complex 4 DNA Figure 9.1a, step 4

  14. Nucleus Cytoplasm Steroidhormone Receptorprotein 1 2 3 Hormone-receptor complex 4 DNA mRNA 5 Figure 9.1a, step 5

  15. Nucleus Cytoplasm Steroidhormone Receptorprotein 1 2 3 Hormone-receptor complex 4 DNA mRNA 5 Newprotein Plasmamembraneof targetcell 6 Figure 9.1a, step 6

  16. Second-Messenger System (Nonsteroid Hormone Action) Hormone binds to a membrane receptor Hormone does not enter the cell Sets off a series of reactions that activates an enzyme Catalyzes a reaction that produces a second-messenger molecule (such as cAMP) Oversees additional intracellular changes to promote a specific response

  17. Nonsteroidhormone (first messenger) Cytoplasm Enzyme ATP 3 1 2 Secondmessenger cAMP 4 Receptorprotein Effect on cellular function, such as glycogenbreakdown Plasma membraneof target cell (b) Nonsteroid hormone action Figure 9.1b

  18. Nonsteroidhormone (first messenger) Cytoplasm 1 Receptorprotein Figure 9.1b, step 1

  19. Nonsteroidhormone (first messenger) Cytoplasm Enzyme 1 2 Receptorprotein Figure 9.1b, step 2

  20. Nonsteroidhormone (first messenger) Cytoplasm Enzyme ATP 3 1 2 Secondmessenger cAMP Receptorprotein Figure 9.1b, step 3

  21. Nonsteroidhormone (first messenger) Cytoplasm Enzyme ATP 3 1 2 Secondmessenger cAMP 4 Receptorprotein Effect on cellular function, such as glycogenbreakdown Plasma membraneof target cell Figure 9.1b, step 4

  22. Control of Hormone Release Hormone levels in the blood are mostly 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

  23. Hormonal Stimuli of Endocrine Glands Most common stimuli Endocrine glands are activated by other hormones Examples: Anterior pituitary hormones travel to target glands, such as the thyroid gland, to prompt the release of a particular hormone, such as thyroid hormone

  24. (a) Hormonal stimulus 1 The hypothalamus secretes hormones that… Hypothalamus 2 …stimulatethe anteriorpituitary gland to secretehormonesthat… Anteriorpituitarygland Thyroidgland Gonad(Testis) Adrenalcortex 3 …stimulate other endocrine glands to secrete hormones Figure 9.2a

  25. Humoral Stimuli of Endocrine Glands Changing blood levels of certain ions stimulate hormone release Humoral indicates various body fluids such as blood and bile Examples: Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels Insulin is produced in response to changing levels of blood glucose levels

  26. (b) Humoral stimulus 1 Capillary blood contains lowconcentration of Ca2+, whichstimulates… Capillary(low Ca2+in blood) Thyroid gland(posterior view) Parathyroidglands Parathyroidglands PTH 2 …secretion of parathyroid hormone (PTH) by parathyroidglands Figure 9.2b

  27. Neural Stimuli of Endocrine Glands Nerve impulses stimulate hormone release Most are under the control of the sympathetic nervous system Examples: The release of norepinephrine and epinephrine by the adrenal medulla

  28. (c) Neural stimulus 1 Preganglionic sympatheticfiber stimulates adrenal medulla cells… CNS (spinal cord) Preganglionicsympathetic fibers Medulla ofadrenalgland Capillary 2 …to secrete catecholamines(epinephrine and norepinephrine) Figure 9.2c

  29. Major Endocrine Organs Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pineal gland Thymus gland Pancreas Gonads (Ovaries and Testes) Hypothalamus

  30. Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 9.3

  31. Pituitary Gland Size of a pea Hangs by a stalk from the hypothalamus in the brain Protected by the sphenoid bone Has two functional lobes Anterior pituitary—glandular tissue Posterior pituitary—nervous tissue Often called the “master endocrine gland”

  32. Hormones of the Anterior Pituitary Six anterior pituitary hormones Two affect non-endocrine targets Growth hormone Prolactin Four stimulate other endocrine glands (tropic hormones) Thyroid-stimulating hormone (thyrotropic hormone) Adrenocorticotropic hormone Two gonadotropic hormones

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

  34. Hypothalamus Hypothalamus Hypothalamus Releasing hormones secreted into portal circulation Anterior pituitary Posterior pituitary Hypophyseal portal system Adrenocorticotropic hormone (ACTH) Growth hormone (GH) Thyrotropic hormone (TH) Adrenal cortex Bones and muscles Prolactin (PRL) Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Mammary glands Thyroid Testes or ovaries Figure 9.4

  35. Hormones of the Anterior Pituitary Growth hormone General metabolic hormone Major effects are directed to growth of skeletal muscles and long bones Plays a role in determining final body size Causes amino acids to be built into proteins Causes fats to be broken down for a source of energy

  36. Hormones of the Anterior Pituitary Growth hormone (GH) disorders Pituitary dwarfism results from hyposecretion of GH during childhood Gigantism results from hypersecretion of GH during childhood Acromegaly results from hypersecretion of GH during adulthood

  37. Pituitary dwarf (left), Giant (center), Normal height woman (right) Figure 9.5

  38. Hormones of the Anterior Pituitary Prolactin (PRL) Stimulates and maintains milk production following childbirth Function in males is unknown Adrenocorticotropic hormone (ACTH) Regulates endocrine activity of the adrenal cortex Thyroid-stimulating hormone (TSH) Influences growth and activity of the thyroid gland

  39. Hormones of the Anterior Pituitary Gonadotropic hormones Regulate hormonal activity of the gonads Follicle-stimulating hormone (FSH) Stimulates follicle development in ovaries Stimulates sperm development in testes Luteinizing hormone (LH) Triggers ovulation of an egg in females Stimulates testosterone production in males

  40. Pituitary–Hypothalamus Relationship Hormonal release is regulated by releasing and inhibiting hormones produced by the hypothalamus Hypothalamus produces two hormones These hormones are transported to neurosecretory cells of the posterior pituitary Oxytocin Antidiuretic hormone The posterior pituitary is not strictly an endocrine gland, but does release hormones

  41. Hormones of the Posterior Pituitary Oxytocin Stimulates contractions of the uterus during labor, sexual relations, and breastfeeding Causes milk ejection in a nursing woman

  42. Hormones of the Posterior Pituitary Antidiuretic hormone (ADH) Inhibits urine production by promoting water reabsorption by the kidneys In large amounts, causes vasoconstriction leading to increased blood pressure Also known as vasopressin

  43. Hypothalamic neurosecretory cells Optic chiasma Hypothalamus Axon terminals Arterial blood supply Posterior lobe Capillary bed Venous drainage Anterior lobe of the pituitary ADH Oxytocin Kidney tubules Mammary glands Uterine muscles Figure 9.6

  44. Thyroid Gland Found at the base of the throat Consists of two lobes and a connecting isthmus Produces two hormones Thyroid hormone Calcitonin

  45. Epiglottis Thyroid cartilage Common carotid artery Isthmus of thyroid gland Trachea Left subclavian artery Brachiocephalic artery Left lobe of thyroid gland Aorta (a) Gross anatomy of the thyroid gland, anterior view Figure 9.7a

  46. Thyroid Gland Thyroid hormone Major metabolic hormone Composed of two active iodine-containing hormones Thyroxine (T4)—secreted by thyroid follicles Triiodothyronine (T3)—conversion of T4 at target tissues

  47. Colloid-filled follicles Follicle cells Parafollicular cell (b) Photomicrograph of thyroid gland follicles (125×) Figure 9.7b

  48. Thyroid Gland Thyroid hormone disorders Goiters Thyroid gland enlarges due to lack of iodine Salt is iodized to prevent goiters Cretinism Caused by hyposecretion of thyroxine Results in dwarfism during childhood

  49. Figure 9.8

  50. Thyroid Gland Thyroid hormone disorders (continued) Myxedema Caused by hypothyroidism in adults Results in physical and mental slugishness Graves’ disease Caused by hyperthyroidism Results in increased metabolism, heat intolerance, rapid heartbeat, weight loss, and exophthalmos

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