Start Here Ch18 Lecture

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  • 1. :) The Endocrine System PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris
  • 2. Introduction to the Endocrine System
    • Figure 18–1 Organs and Tissues of the Endocrine System.
  • 3. Introduction to the Endocrine System
    • Figure 18–1 Organs and Tissues of the Endocrine System.
    :)
  • 4. Introduction to the Endocrine System
    • The Endocrine System
      • Regulates long-term processes
        • Growth
        • Development
        • Reproduction
      • Uses chemical messengers to relay information and instructions between cells
    :)
  • 5. Homeostasis and Intercellular Communication
    • Direct Communication
      • Exchange of ions and molecules between adjacent cells across gap junctions
      • Occurs between two cells of same type
      • Highly specialized and relatively rare
    :)
  • 6. Homeostasis and Intercellular Communication
    • Paracrine Communication
      • Uses chemical signals to transfer information from cell to cell within single tissue
      • Most common form of intercellular communication
    :)
  • 7. Homeostasis and Intercellular Communication
    • Endocrine Communication
      • Endocrine cells release chemicals ( hormones ) into bloodstream
      • Alters metabolic activities of many tissues and organs simultaneously
    :)
  • 8. Homeostasis and Intercellular Communication
    • Target Cells
      • Are specific cells that possess receptors needed to bind and “read” hormonal messages
    • Hormones
      • Stimulate synthesis of enzymes or structural proteins
      • Increase or decrease rate of synthesis
      • Turn existing enzyme or membrane channel “on” or “off”
    :)
  • 9. Homeostasis and Intercellular Communication :)
  • 10. Homeostasis and Intercellular Communication :)
  • 11. Hormones
    • Can be divided into three groups
      • Amino acid derivatives
      • Peptide hormones
      • Lipid derivatives
    • Circulate freely or bound to transport proteins
    :)
  • 12. Hormones
    • Figure 18–2 A Structural Classification of Hormones
    :)
  • 13. Secretion and Distribution of Hormones
    • Free Hormones
      • Remain functional for less than 1 hour
        • Diffuse out of bloodstream:
          • bind to receptors on target cells
        • Are broken down and absorbed:
          • by cells of liver or kidney
        • Are broken down by enzymes:
          • in plasma or interstitial fluids
    :)
  • 14. Secretion and Distribution of Hormones
    • Thyroid and Steroid Hormones
      • Remain in circulation much longer
      • Enter bloodstream
        • More than 99% become attached to special transport proteins
        • Bloodstream contains substantial reserve of bound hormones
    :)
  • 15. Mechanisms of Hormone Action
    • Hormone Receptor
      • Is a protein molecule to which a particular molecule binds strongly
      • Responds to several different hormones
      • Different tissues have different combinations of receptors
      • Presence or absence of specific receptor determines hormonal sensitivity
    :)
  • 16. Mechanisms of Hormone Action
    • Hormones and Plasma Membrane Receptors
      • Catecholamines and peptide hormones
        • Are not lipid soluble
        • Unable to penetrate plasma membrane
        • Bind to receptor proteins at outer surface of plasma membrane (extracellular receptors)
    :)
  • 17. Mechanisms of Hormone Action
    • Hormones and Plasma Membrane Receptors
      • Bind to receptors in plasma membrane
      • Cannot have direct effect on activities inside target cell
      • Use intracellular intermediary to exert effects
        • First messenger:
          • leads to second messenger
          • may act as enzyme activator, inhibitor, or cofactor
          • results in change in rates of metabolic reactions
    :)
  • 18. Mechanisms of Hormone Action
    • Important Second Messengers
      • Cyclic-AMP (cAMP)
        • Derivative of ATP
      • Cyclic-GMP (cGMP)
        • Derivative of GTP
      • Calcium ions
    :)
  • 19. Mechanisms of Hormone Action
    • The Process of Amplification
      • Is the binding of a small number of hormone molecules to membrane receptors
      • Leads to thousands of second messengers in cell
      • Magnifies effect of hormone on target cell
    :)
  • 20. Mechanisms of Hormone Action
    • Down-regulation
      • Presence of a hormone triggers decrease in number of hormone receptors
      • When levels of particular hormone are high, cells become less sensitive
    • Up-regulation
      • Absence of a hormone triggers increase in number of hormone receptors
      • When levels of particular hormone are low, cells become more sensitive
    :)
  • 21. Mechanisms of Hormone Action
    • Hormones and Plasma Membrane Receptors
      • G Protein
        • Enzyme complex coupled to membrane receptor
        • Involved in link between first messenger and second messenger
        • Binds GTP
        • Activated when hormone binds to receptor at membrane surface and changes concentration of second messenger cyclic-AMP (cAMP) within cell:
          • increased cAMP level accelerates metabolic activity within cell
    :)
  • 22. Mechanisms of Hormone Action
    • Figure 18–3 G Proteins and Hormone Activity.
    :)
  • 23. Mechanisms of Hormone Action
    • Figure 18–3 G Proteins and Hormone Activity.
    :)
  • 24. Mechanisms of Hormone Action
    • G Proteins and Calcium Ions
      • Activated G proteins trigger
        • opening of calcium ion channels in membrane
        • release of calcium ions from intracellular stores
        • G protein activates enzyme phospholipase C (PLC)
        • Enzyme triggers receptor cascade:
          • production of diacylglycerol (DAG) and inositol triphosphate (IP 3 ) from membrane phospholipids
    :)
  • 25. Mechanisms of Hormone Action
    • Figure 18–3 G Proteins and Hormone Activity.
    :)
  • 26. Mechanisms of Hormone Action
    • Hormones and Intracellular Receptors
      • Alter rate of DNA transcription in nucleus
        • Change patterns of protein synthesis
      • Directly affect metabolic activity and structure of target cell
      • Includes steroids and thyroid hormones
    :)
  • 27. Mechanisms of Hormone Action
    • Figure 18–4a Effects of Intracellular Hormone Binding.
    :)
  • 28. Mechanisms of Hormone Action
    • Figure 18–4b Effects of Intracellular Hormone Binding.
    :)
  • 29. Endocrine Reflexes
    • Endocrine Reflexes
      • Functional counterparts of neural reflexes
      • In most cases, controlled by negative feedback mechanisms
        • Stimulus triggers production of hormone whose effects reduce intensity of the stimulus
    :)
  • 30. Endocrine Reflexes
    • Endocrine reflexes can be triggered by
      • Humoral stimuli
        • Changes in composition of extracellular fluid
      • Hormonal stimuli
        • Arrival or removal of specific hormone
      • Neural stimuli
        • Arrival of neurotransmitters at neuroglandular junctions
    :)
  • 31. Endocrine Reflexes
    • Simple Endocrine Reflex
      • Involves only one hormone
      • Controls hormone secretion by the heart, pancreas, parathyroid gland, and digestive tract
    • Complex Endocrine Reflex
      • Involves
        • One or more intermediary steps
        • Two or more hormones
        • The hypothalamus
    :)
  • 32. Endocrine Reflexes
    • Figure 18–5 Three Mechanisms of Hypothalamic Control over Endocrine Function.
    :)
  • 33. Endocrine Reflexes
    • Neuroendocrine Reflexes
      • Pathways include both neural and endocrine components
    • Complex Commands
      • Issued by changing
        • Amount of hormone secreted
        • Pattern of hormone release:
          • hypothalamic and pituitary hormones released in sudden bursts
          • frequency changes response of target cells
    :)
  • 34. The Pituitary Gland
    • Also called hypophysis
    • Lies within sella turcica
      • Diaphragma sellae
        • A dural sheet that locks pituitary in position
        • Isolates it from cranial cavity
    • Hangs inferior to hypothalamus
      • Connected by infundibulum
    :)
  • 35. Pituitary Gland
    • Releases nine important peptide hormones
    • Hormones bind to membrane receptors
      • Use cAMP as second messenger
    :)
  • 36. Pituitary Gland
    • Figure 18–6a The Anatomy and Orientation of the Pituitary Gland.
    :)
  • 37. Pituitary Gland
    • Figure 18–6b The Anatomy and Orientation of the Pituitary Gland.
    :)
  • 38. Pituitary Gland
    • Median Eminence
      • Swelling near attachment of infundibulum
      • Where hypothalamic neurons release regulatory factors
        • Into interstitial fluids
        • Through fenestrated capillaries
    :)
  • 39. Pituitary Gland
    • Portal Vessels
      • Blood vessels link two capillary networks
      • Entire complex is portal system
        • Ensures that regulatory factors reach intended target cells before entering general circulation
    :)
  • 40. Pituitary Gland
    • Figure 18–7 The Hypophyseal Portal System and the Blood Supply to the Pituitary Gland.
    :)
  • 41. Pituitary Gland
    • Two Classes of Hypothalamic Regulatory Hormones
      • Releasing hormones (RH)
        • Stimulate synthesis and secretion of one or more hormones at anterior lobe
      • Inhibiting hormones (IH)
        • Prevent synthesis and secretion of hormones from the anterior lobe
    • Rate of secretion is controlled by negative feedback
    :)
  • 42. Pituitary Gland
    • Anterior lobe (also called adenohypophysis )
      • Hormones “turn on” endocrine glands or support other organs
      • Can be subdivided into three regions:
        • Pars distalis
        • Pars intermedia
        • Pars tuberalis
    :)
  • 43. Pituitary Gland
    • Figure 18–8a Feedback Control of Endocrine Secretion
    :)
  • 44. Pituitary Gland
    • Figure 18–8b Feedback Control of Endocrine Secretion.
    :)
  • 45. Pituitary Gland
    • Figure 18–9 Pituitary Hormones and Their Targets.
    :)
  • 46. Pituitary Gland :)
  • 47. Pituitary Gland
    • Posterior lobe (also called neurohypophysis)
      • Contains unmyelinated axons of hypothalamic neurons
      • Supraoptic and paraventricular nuclei manufacture
        • Antidiuretic hormone (ADH)
        • Oxytocin (OXT)
    :)
  • 48. Pituitary Gland
    • Figure 18–9 Pituitary Hormones and Their Targets.
    :)
  • 49. Pituitary Gland :)
  • 50. The Thyroid Gland
    • Lies anterior to thyroid cartilage of larynx
    • Consists of two lobes connected by narrow isthmus
      • Thyroid follicles
        • Hollow spheres lined by cuboidal epithelium
        • Cells surround follicle cavity that contains viscous colloid
        • Surrounded by network of capillaries that
          • deliver nutrients and regulatory hormones
          • accept secretory products and metabolic wastes
    :)
  • 51. The Thyroid Gland
    • Thyroglobulin (Globular Protein)
      • Synthesized by follicle cells
      • Secreted into colloid of thyroid follicles
      • Molecules contain the amino acid tyrosine
    • Thyroxine (T 4 )
      • Also called tetraiodothyronine
      • Contains four iodide ions
    • Triiodothyronine (T 3 )
      • Contains three iodide ions
    :)
  • 52. The Thyroid Gland
    • Figure 18–10a The Thyroid Gland.
    :)
  • 53. The Thyroid Gland
    • Figure 18–10b-c The Thyroid Gland.
    :)
  • 54. The Thyroid Gland
    • Figure 18–11a The Thyroid Follicles: Synthesis, Storage, and Secretion of Thyroid Hormones.
    :)
  • 55. The Thyroid Gland
    • Figure 18–11b The Thyroid Follicles: The Regulation of Thyroid Secretion.
    :)
  • 56. The Thyroid Gland
    • Thyroid-Stimulating Hormone (TSH)
      • Absence causes thyroid follicles to become inactive
        • Neither synthesis nor secretion occurs
      • Binds to membrane receptors
      • Activates key enzymes in thyroid hormone production
    :)
  • 57. The Thyroid Gland
    • Thyroid Hormones
      • Enter target cells by transport system
      • Affect most cells in body
      • Bind to receptors in
        • Cytoplasm
        • Surfaces of mitochondria
        • Nucleus
      • In children, essential to normal development of
        • Skeletal, muscular, and nervous systems
    :)
  • 58. The Thyroid Gland
    • Calorigenic Effect
      • Cell consumes more energy resulting in increased heat generation
      • Is responsible for strong, immediate, and short-lived increase in rate of cellular metabolism
    :)
  • 59. The Thyroid Gland :)
  • 60. The Thyroid Gland
    • C (Clear) Cells of the Thyroid Gland
      • Produce calcitonin (CT)
        • Helps regulate concentrations of Ca 2+ in body fluids
    :)
  • 61. Parathyroid Glands
    • Embedded in posterior surface of thyroid gland
    • Parathyroid hormone (PTH)
      • Produced by chief cells
      • In response to low concentrations of Ca 2+
    :) Figure 18–12
  • 62. Parathyroid Glands
    • Figure 18–12 The Parathyroid Glands.
    :)
  • 63. Parathyroid Glands
    • Four Effects of PTH
      • It stimulates osteoclasts
        • Accelerates mineral turnover and releases Ca 2+ from bone
      • It inhibits osteoblasts
        • Reduces rate of calcium deposition in bone
      • It enhances reabsorption of Ca 2+ at kidneys, reducing urinary loss
      • It stimulates formation and secretion of calcitriol at kidneys
        • Effects complement or enhance PTH
        • Enhances Ca 2+ , PO 4 3- absorption by digestive tract
    :) Figure 18–12
  • 64. Parathyroid Glands
    • Figure 18–13 The Homeostatic Regulation of Calcium Ion Concentrations.
    :)
  • 65. Parathyroid Glands :)
  • 66. Suprarenal (Adrenal) Glands
    • Lie along superior border of each kidney
    • Subdivided into
      • Superficial suprarenal cortex
        • Stores lipids, especially cholesterol and fatty acids
        • Manufactures steroid hormones: adrenocortical steroids (corticosteroids)
      • Inner suprarenal medulla
        • Secretory activities controlled by sympathetic division of ANS
        • Produces epinephrine (adrenaline) and norepinephrine
        • Metabolic changes persist for several minutes
    :)
  • 67. Suprarenal (Adrenal) Glands
    • Suprarenal Cortex
      • Subdivided into three regions:
        • Zona glomerulosa
        • Zona fasciculata
        • Zona reticularis
    :)
  • 68. Suprarenal Glands
    • Zona Glomerulosa
      • Outer region of suprarenal cortex
      • Produces mineralocorticoids
        • For example, aldosterone:
          • stimulates conservation of sodium ions and elimination of potassium ions
          • increases sensitivity of salt receptors in taste buds
        • Secretion responds to:
          • drop in blood Na + , blood volume, or blood pressure
          • rise in blood K + concentration
    :)
  • 69. Suprarenal Glands
    • Zona Fasciculata
      • Produces glucocorticoids
      • For example, cortisol (hydrocortisone) with corticosterone
        • Liver converts cortisol to cortisone
      • Secretion regulated by negative feedback
      • Has inhibitory effect on production of
        • Corticotropin-releasing hormone (CRH) in hypothalamus
        • ACTH in adenohypophysis
    :)
  • 70. Suprarenal Glands
    • Zona Fasciculata (cont’d)
      • Accelerates glucose synthesis and glycogen formation
      • Shows anti-inflammatory effects
        • Inhibits activities of white blood cells and other components of immune system
    :)
  • 71. Suprarenal Glands
    • Zona Reticularis
      • Network of endocrine cells
      • Forms narrow band bordering each suprarenal medulla
      • Produces androgens under stimulation by ACTH
    :)
  • 72. Suprarenal Glands
    • Figure 18–14a The Suprarenal Gland.
    :)
  • 73. Suprarenal Glands
    • Figure 18–14b-c The Suprarenal Gland.
    :)
  • 74. Suprarenal Glands
    • Suprarenal Medulla
      • Contains two types of secretory cells
        • One produces epinephrine (adrenaline)
          • 75 to 80% of medullary secretions
        • The other produces norepinephrine (noradrenaline)
          • 20 to 25% of medullary secretions
    :)
  • 75. Suprarenal Glands :)
  • 76. Pineal Gland
    • Lies in posterior portion of roof of third ventricle
    • Contains pinealocytes
      • Synthesize hormone melatonin
    :)
  • 77. Pineal Gland
    • Functions of Melatonin
      • Inhibiting reproductive functions
      • Protecting against damage by free radicals
      • Setting circadian rhythms
    :)
  • 78. Pancreas
    • Lies between
      • Inferior border of stomach
      • And proximal portion of small intestine
    • Contains exocrine and endocrine cells
    :)
  • 79. Pancreas
    • Endocrine Pancreas
      • Consists of cells that form clusters known as pancreatic islets , or islets of Langerhans
        • Alpha cells produce glucagon
        • Beta cells produce insulin
        • Delta cells produce peptide hormone identical to GH-IH
        • F cells secrete pancreatic polypeptide (PP)
    :)
  • 80. Pancreas
    • Figure 18–15 The Endocrine Pancreas
    :)
  • 81. Pancreas
    • Figure 18–15 The Endocrine Pancreas
    :)
  • 82. Pancreas
    • Blood Glucose Levels
      • When levels rise
        • Beta cells secrete insulin, stimulating transport of glucose across plasma membranes
      • When levels decline
        • Alpha cells release glucagon, stimulating glucose release by liver
    :)
  • 83. Pancreas
    • Figure 18–16 The Regulation of Blood Glucose Concentrations
    :)
  • 84. Pancreas
    • Insulin
      • Is a peptide hormone released by beta cells
      • Affects target cells
        • Accelerates glucose uptake
        • Accelerates glucose utilization and enhances ATP production
        • Stimulates glycogen formation
        • Stimulates amino acid absorption and protein synthesis
        • Stimulates triglyceride formation in adipose tissue
    :)
  • 85. Pancreas
    • Glucagon
      • Released by alpha cells
      • Mobilizes energy reserves
      • Affects target cells
        • Stimulates breakdown of glycogen in skeletal muscle and liver cells
        • Stimulates breakdown of triglycerides in adipose tissue
        • Stimulates production of glucose in liver
    :)
  • 86. Pancreas :)
  • 87. Pancreas :)
  • 88. Endocrine Tissues of Other Systems
    • Many organs of other body systems have secondary endocrine functions
      • Intestines (digestive system)
      • Kidneys (urinary system)
      • Heart (cardiovascular system)
      • Thymus (lymphoid system and immunity)
      • Gonads (reproductive system)
    :)
  • 89. Endocrine Tissues of Other Systems
    • Intestines
      • Produce hormones important to coordination of digestive activities
    • Kidneys
      • Produce the hormones calcitriol and erythropoietin
      • Produce the enzyme renin
    :)
  • 90. Endocrine Tissues of Other Systems
    • Figure 18–17a Endocrine Functions of the Kidneys: The Production of Calcitriol
    :)
  • 91. Endocrine Tissues of Other Systems
    • Figure 18–17b Endocrine Functions of the Kidneys: Overview of the Renin-angiotensin System
    :)
  • 92. Endocrine Tissues of Other Systems
    • Heart
      • Produces natriuretic peptides ( ANP and BNP )
        • When blood volume becomes excessive
        • Action opposes angiotensin II
        • Resulting in reduction in blood volume and blood pressure
    • Thymus
      • Produces thymosins (blend of thymic hormones)
        • That help develop and maintain normal immune defenses
    :)
  • 93. Endocrine Tissues of Other Systems :)
  • 94. Endocrine Tissues of Other Systems
    • Testes (Gonads)
      • Produce androgens in interstitial cells
        • Testosterone is the most important male hormone
      • Secrete inhibin in nurse (sustentacular) cells
        • Support differentiation and physical maturation of sperm
    :)
  • 95. Endocrine Tissues of Other Systems
    • Ovaries (Gonads)
      • Produce estrogens
        • Principle estrogen is estradiol
      • After ovulation, follicle cells
        • Reorganize into corpus luteum
        • Release estrogens and progestins , especially progesterone
    :)
  • 96. Endocrine Tissues of Other Systems :)
  • 97. Endocrine Tissues of Other Systems
    • Adipose Tissue Secretions
      • Leptin
        • Feedback control for appetite
        • Controls normal levels of GnRH, gonadotropin synthesis
      • Resistin
        • Reduces insulin sensitivity
    :)
  • 98. Hormone Interactions
    • Antagonistic (opposing) effects
    • Synergistic (additive) effects
    • Permissive effects: one hormone is necessary for another to produce effect
    • Integrative effects: hormones produce different and complementary results
    :)
  • 99. Hormone Interactions
    • Hormones Important to Growth
      • GH
      • Thyroid hormones
      • Insulin
      • PTH
      • Calcitriol
      • Reproductive hormones
    :)
  • 100. Hormone Interactions
    • Growth Hormone (GH)
      • In children
        • Supports muscular and skeletal development
      • In adults
        • Maintains normal blood glucose concentrations
        • Mobilizes lipid reserves
    :)
  • 101. Hormone Interactions
    • Thyroid Hormones
      • If absent during fetal development or for first year
        • Nervous system fails to develop normally
        • Mental retardation results
      • If T 4 concentrations decline before puberty
        • Normal skeletal development will not continue
    :)
  • 102. Hormone Interactions
    • Insulin
      • Allows passage of glucose and amino acids across plasma membranes
    • Parathyroid Hormone (PTH) and Calcitriol
      • Promote absorption of calcium salts for deposition in bone
      • Inadequate levels causes weak and flexible bones
    :)
  • 103. Hormone Interactions
    • Reproductive Hormones
      • Androgens in males, estrogens in females
      • Stimulate cell growth and differentiation in target tissues
      • Produce gender-related differences in
        • Skeletal proportions
        • Secondary sex characteristics
    :)
  • 104. Hormone Interactions :)
  • 105. Hormone Interactions :)
  • 106. Hormone Interactions
    • General Adaptation Syndrome (GAS)
      • Also called stress response
      • How body responds to stress-causing factors
      • Is divided into three phases:
        • Alarm phase
        • Resistance phase
        • Exhaustion phase
    :) Figure 18–18
  • 107. Hormone Interactions
    • Figure 18–18 The General Adaptation Syndrome.
    :)
  • 108. Hormone Interactions
    • Figure 18–18 The General Adaptation Syndrome.
    :)
  • 109. Hormone Interactions
    • Figure 18–18 The General Adaptation Syndrome.
    :)
  • 110. Hormone Interactions
    • Hormone Changes
      • Can alter intellectual capabilities, memory, learning, and emotional states
      • Affect behavior when endocrine glands are over-secreting or under-secreting
    • Aging
      • Causes few functional changes
      • Decline in concentration of
        • Growth hormone
        • Reproductive hormones
    :)
  • 111. Hormone Interactions
    • Figure 18–19 Functional Relationships between the Endocrine System and Other Systems
    :)
  • 112. Hormone Interactions
    • Figure 18–19 Functional Relationships between the Endocrine System and Other Systems
    :)
  • 113. Hormone Interactions
    • Figure 18–19 Functional Relationships between the Endocrine System and Other Systems
    :)