12.0 The Endocrine System.pdf

1. The Endocrine System Human Anatomy & Physiology

2. Endocrine System Overview

3. • Endocrine system acts with nervous system of body cells • Influences metabolic activities via hormones transported in blood • Responses are slower but longer lasting than nervous system responses • Endocrinology: study of hormones and endocrine organs Endocrine System Overview

4. Endocrine System Controls and integrates body processes Regulation of cellular metabolism and energy balance Mobilization of body defenses Reproduction Growth and development Maintenance of electrolyte, water, and nutrient balance of blood

5. Types of Glands Exocrine glands • Produce non-hormonal substances (examples: sweat, saliva) • Have ducts to carry secretions to membrane surface Endocrine glands • Produce hormones • Lack ducts Secretions Duct Surface Gland lumen

6. Types of Glands Blood in capillaries Hormones being secreted into blood Exocrine glands • Produce non-hormonal substances (examples: sweat, saliva) • Have ducts to carry secretions to membrane surface Endocrine glands • Produce hormones • Lack ducts

7. Endocrine System Overview Pancreas Gonads (ovaries) Placenta Organs with exocrine and endocrine functions Pineal gland Adrenal glands Pituitary gland Trachea Parathyroid glands (on posterior side of thyroid) Thyroid gland Hypothalamus

8. Other tissues and organs that produce hormones: • Adipose cells • Thymic cells Endocrine System Overview Adipose cell

9. Other tissues and organs that produce hormones: • Adipose cells • Thymic cells Endocrine System Overview Duodenum Small intestine Stomach Jejunum Ileum Heart Kidneys

10. Long-distance chemical signals that travel in blood or lymph Chemicals that exert effects on the same cells that secrete them Locally acting chemicals that affect cells nearby without affecting those that secrete them Chemical Messengers Hormones Autocrines Paracrines Autocrine and paracrine hormones are not considered part of endocrine system

11. Hormone Chemical Structure

12. Hormone Chemical Structure Amino acid-based hormones Steroids • Amino acid derivatives, peptides, and proteins • Synthesized from cholesterol • Gonadal and adrenocortical hormones Two main classes of hormones: A possible third class, eicosanoids, is considered a hormone by some scientists, but most classify it as a paracrine.

13. Action of Hormones

14. Action of Hormones Target cell Target cell Hormones alter target cell activity. Blood vessel Hormone Secreting cell Receptor

15. Action of Hormones Stimulate synthesis of enzymes or other proteins Induce secretory activity Activate or deactivate enzymes Stimulate mitosis Alter plasma membrane permeability and/or membrane potential by opening or closing ion channels Hormone action on target cells may be to:

16. Action of Hormones 1. Water-soluble hormones (all amino acid-based hormones except thyroid hormone) • Act on plasma membrane receptors • Act via G protein second messengers • Cannot enter cell 2. Lipid-soluble hormones (steroid and thyroid hormones) • Act on intracellular receptors that directly activate genes • Can enter cell Hormones act in one of two ways, depending on their chemical nature and receptor location.

17. Amino acid-based hormones, except thyroid hormone, exert effects through second messenger systems. Second Messenger Systems

18. Second Messenger Systems 1. Water-soluble hormones (all amino acid-based hormones except thyroid hormone) Cyclic AMP PIP2- calcium

19. Cyclic AMP (cAMP) Signaling Mechanism 1. Water-soluble hormones (all amino acid-based hormones except thyroid hormone) Receptor Hormone Cytoplasm G protein complex (stimulatory) Adenylate cyclase AC ATP cAMP Adenosine triphosphate PKA Protein kinase Phosphorylation cascade Phosphodiesterase (stops signal transduction pathway) -AMP PDE4 PDE4i activates Amplification effect

20. PIP2-Calcium Signaling Mechanism Protein kinase C Phosphorylation of target proteins Phospholipase C G protein coupled receptor IP3/Ca2+ channel Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Protein kinase Cellular response 1. Water-soluble hormones (all amino acid-based hormones except thyroid hormone) DAG (diacylglycerol) (Inositol trisphosphate) IP3 Hormone PIP2 Calmodulin

21. 1. Lipid-soluble steroid hormones and thyroid hormone can diffuse into target cells and bind with intracellular receptors. 2. Receptor-hormone complex enters nucleus and binds to a specific region of the DNA. Intracellular Receptors: Direct Gene Activation Lipid-soluble hormone 2. Lipid-soluble hormones (steroid and thyroid hormones) Cytoplasm Nucleus Plasma membrane Intracellular receptor

22. Intracellular Receptors: Direct Gene Activation Lipid-soluble hormone 3. Receptor-hormone complex helps initiate DNA transcription to produce mRNA. 4. mRNA is then translated into specific protein. • Proteins synthesized have various functions, e.g.: metabolic activities, structural purposes, or being exported from the cell. 2. Lipid-soluble hormones (steroid and thyroid hormones) Cytoplasm Nucleus Plasma membrane Intracellular receptor New protein

23. Hormone Release

24. Hormone Release Blood levels of hormones • Controlled by negative feedback systems • Levels vary only within narrow, desirable range • Hormone release is triggered by: • Endocrine gland stimuli • Nervous system modulation Homeostasis Correction: ↑ hormone 3 Imbalance: trigger Negative feedback 4 Hormone release 2 1

25. Endocrine Gland Stimuli Humoral stimuli Neural stimuli Hormonal stimuli Endocrine glands are stimulated to synthesize and release hormones in response to one of 3 stimuli:

26. Parathyroid Hormone (PTH) Blood vessel Ca2+ Low blood levels of Ca2+ + Changing blood levels of ions and nutrients directly stimulate secretion of hormones PTH Calcium is released into bloodstream Rising levels of Ca2+ +

27. • Nerve fibers stimulate hormone release • Example: sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines Neural Stimuli CNS (spinal cord) Medulla of adrenal gland Sympathetic fibers Capillary Hormones e.g., catecholamines

28. Hormonal Stimuli © by Lecturio Anterior pituitary + + + + + + • Hormones stimulate other endocrine organs to release their hormones. • Example: hormones of the hypothalamus Hypothalamus

29. The nervous system can make adjustments to hormone levels when needed. It can modify stimulation or inhibition of endocrine glands. The nervous system can override normal endocrine controls. Nervous System Modulation

30. Target Cell Specificity

31. Target cells must have specific receptors to which hormones bind. For example, ACTH receptors are found only on certain cells of the adrenal cortex, but thyroxin receptors are found on nearly all cells of the body. Target Cell Specificity

32. Target Cell Specificity Affinity (strength) of binding between receptor and hormone Relative number of receptors on/in target cell Blood levels of hormone Target cell activation depends on 3 factors:

33. Target Cell Specificity The amount of hormone can influence the number of receptors for that hormone • Up-regulation: target cells form more receptors in response to low hormone levels • Down-regulation: target cells lose receptors in response to high hormone levels • Desensitizes the target cells to prevent them from overreacting to persistently high levels of hormone Up-regulation Down-regulation Hormone Target cell Hormone receptor Time Time Hormone Target cell Hormone receptor

34. Hormone Circulation Blood vessel Free hormone Endocrine cell Hormones circulate in the blood either free or bound. • Steroids and thyroid hormone are attached to plasma proteins. • All others circulate without carriers. Bound to carrier proteins

35. Hormone Circulation Blood vessel Free hormone Endocrine cell Concentration of circulating hormone reflects: • Rate of release • Speed at which it is inactivated and removed from the body Bound to carrier proteins

36. Degrading enzymes Liver Kidneys Hormone Circulation Hormones can be removed from the blood by:

37. Half-life is the time required for the level of hormone in blood level to decrease by half. It varies anywhere from a fraction of a minute to a week, depending on the hormone. Half-life of Hormone Activity

38. Onset of Hormone Activity Hormones have different response times: • Some responses are immediate. • Some, especially steroids, can take hours to days. • Some are inactive until they enter target cells.

39. Duration of Hormone Activity The duration of the response is usually limited. • It ranges from 10 seconds to several hours. • Effects may disappear rapidly as blood levels drop, but some may persist for hours at low blood levels.

40. Permissiveness Synergism • One hormone cannot exert its effects without another hormone being present. • Example: Reproductive hormones need thyroid hormone to have effect. • More than one hormone produces the same effects on a target cell, causing amplification. • Example: Glucagon and epinephrine both cause the liver to release glucose. Interaction of Hormones at Target Cells Multiple hormones may act on the same target at the same time. Antagonism • One or more hormones oppose the action of another hormone. • Example: Insulin decreases blood glucose levels while glucagon increases blood glucose levels.

41. The Hypothalamus

42. The Hypothalamus and Pituitary Gland Pituitary gland Hypothalamus • The hypothalamus is connected to the pituitary gland (hypophysis) via a stalk called the infundibulum. • The pituitary secretes at least 8 major hormones. Infundibulum Thalamus

43. The Hypothalamus and Pituitary Gland Hypothalamus Infundibulum Thalamus Posterior pituitary: composed of neural tissue that secretes neurohormones Anterior pituitary

44. The Hypothalamus and Pituitary Gland Anterior pituitary Hypothalamus Infundibulum + Posterior lobe = Neurohypophysis Thalamus Posterior pituitary

45. The Hypothalamus and Pituitary Gland Hypothalamus Infundibulum + Posterior lobe = Neurohypophysis Thalamus Posterior pituitary Anterior pituitary (adenohypophysis): consists of glandular tissue

46. The Hypothalamus and Pituitary Gland Pituitary gland • The hypothalamus is connected to the pituitary gland (hypophysis) via a stalk called the infundibulum. • The pituitary secretes at least 8 major hormones. Hypothalamus

47. Posterior Pituitary-hypothalamic Relationships Capillary plexus Hypothalamo- hypophyseal tract Posterior pituitary gland The posterior lobe is neural tissue derived from a downgrowth of the brain. Hormones are stored in axon terminals in the posterior pituitary and are released into the blood when neurons fire. • Paraventricular neurons produce oxytocin (OT) • Supraoptic neurons produce antidiuretic hormone (ADH) ADH release OT release Hypothalamus Infundibulum Pituitary gland ADH release OT release

48. Posterior Pituitary-hypothalamic Relationships Hypothalamo- hypophyseal tract Antidiuretic hormone (ADH) Oxytocin (OT) Hypothalamus Infundibulum Pituitary gland Neurons of supraoptic nucleus: ADH production Neurons of paraventricular nucleus: OT production Posterior pituitary (neural tissue) Axon terminals

49. Posterior Pituitary and Hypothalamic Hormones Paraventricular neurons produce oxytocin (OT) Supraoptic neurons produce antidiuretic hormone (ADH) Posterior pituitary consists of axon terminals of neurons from hypothalamic neurons:

50. Oxytocin Effects • Stimulates uterine contractions during childbirth • Triggers milk ejection • Acts as neurotransmitter in the brain (PIP2-calcium second messenger system) Both positive feedback mechanisms More oxytocin needed Uterine contractions 3 Posterior pituitary Positive feedback 4 Oxytocin release 2 1

51. Antidiuretic Hormone (ADH) Osmoreceptor cells in hypothalamus monitor solute concentration Posterior pituitary: release of ADH Kidney tubules reabsorb more water and prevent urine formation Inhibited by: alcohol, diuretics High concentrations cause vasoconstriction (ADH = vasopressin) + Triggered by: • Solute concentration = too high • Pain • Low blood pressure • Drugs +

52. Anterior Pituitary-hypothalamic Relationships Posterior pituitary gland The hypothalamus secretes releasing and inhibiting hormones to the anterior pituitary to regulate hormone secretion. Hypothalamus Infundibulum Pituitary gland Anterior pituitary gland

53. The hypothalamus secretes releasing and inhibiting hormones to the anterior pituitary to regulate hormone secretion. Pituitary-hypothalamic Relationships

54. Anterior Pituitary Hormones All 6 hormones are peptide hormones. LH FSH TSH PRL GH ACTH • Luteinizing hormone (LH) • Follicle-stimulating hormone (FSH) • Thyroid-stimulating hormone (TSH) • Prolactin (PRL) • Growth hormone (GH) • Adrenocorticotropic hormone (ACTH)

55. Anterior Pituitary Hormones All but growth hormone (GH) activate target cells via cAMP second messenger system. LH FSH TSH PRL GH ACTH • Luteinizing hormone (LH) • Follicle-stimulating hormone (FSH) • Thyroid-stimulating hormone (TSH) • Prolactin (PRL) • Growth hormone (GH) • Adrenocorticotropic hormone (ACTH)

56. Anterior Pituitary Hormones All but 2 are tropic hormones (tropins) that regulate the secretion of other hormones. LH FSH TSH PRL GH ACTH • Luteinizing hormone (LH) • Follicle-stimulating hormone (FSH) • Thyroid-stimulating hormone (TSH) • Prolactin (PRL) • Growth hormone (GH) • Adrenocorticotropic hormone (ACTH)

57. GH is also called somatotropin as it is produced by somatotropic cells. It has direct actions on metabolism and indirect growth-promoting actions. Growth Hormone (GH)

58. Growth Hormone (GH) Fatty acids • Tropic hormone, also called somatotropin • Origin: somatotropic cells • Function: direct actions on metabolism and indirect growth-promoting actions Direct actions on metabolism Indirect actions on growth • Glucose-sparing actions decrease rate of cellular glucose uptake and metabolism (anti-insulin effects) • Triggers liver to break down glycogen into glucose • Increases blood levels of fatty acids for use as fuel and encourages cellular protein synthesis

59. Growth Hormone (GH) Direct actions on metabolism Indirect actions on growth • GH triggers liver, skeletal muscle, and bone to produce insulin-like growth factors (IGFs) • IGFs stimulate cellular uptake of nutrients to: • Synthesize DNA and proteins needed for cell division • Form of collagen • Deposit of bone matrix • GH stimulates most cells to enlarge and divide (major targets: bone and skeletal muscle) • Tropic hormone, also called somatotropin • Origin: somatotropic cells • Function: direct actions on metabolism and indirect growth-promoting actions IGF-1 release

60. Growth Hormone (GH) Regulation of Secretion GH release or inhibition is chiefly regulated by hypothalamic hormones on somatotropic cells. Hypothalamus GHRH Pituitary GH + GHIH/SST GH IGF-I Liver + Stomach Ghrelin GH in blood Glucose (hypoglycemia) Amino acids

61. Negative Feedback Loop for TSH Stimulates Inhibits Thyroid gland Thyroid hormones Target cells Anterior pituitary TSH (Thyrotropin) Hypothalamus ↑ Thyroid hormones GHIH TRH (Thyrotropin-releasing hormone)

62. • Also called corticotropin • Origin: corticotropic cells • Precursor: pro- opiomelanocortin • Function: stimulates adrenal cortex to release corticosteroids Adrenocorticotropic Hormone (ACTH) Anterior pituitary Adrenal cortex ACTH Corticosteroid Hypothalamus CRH

63. • Internal and external factors that alter release of CRH include fever, hypoglycemia, and stressors Adrenocorticotropic Hormone (ACTH) Anterior pituitary Adrenal cortex ACTH Corticosteroid Hypothalamus CRH

64. Gonadotropins (FSH and LH) Male testes Female ovaries + Anterior pituitary Hypothalamus GnRH LH, FSH Sex hormones + Testosterone Estradiol progesterone + + LH and FSH both absent from blood in prepubertal boys and girls

65. • Origin: prolactin cells of anterior pituitary • Function: stimulates milk production in females role in males not well understood Prolactin (PRL) Hypothalamus Pituitary Breast TRH Dopamine/PIH PRL Breast milk production + • Mechanical stimulus • Increased estrogen levels (suckling)

66. Prolactin (PRL) Increased estrogen levels stimulate PRL Reason behind breast swelling and tenderness during menstrual cycle Rising blood levels toward end of pregnancy Suckling stimulates PRL release and promotes continued milk production

67. Thyroid Gland

68. Isthmus: median mass connecting two lateral lobes Thyroid Gland Location and Structure Follicles: hollow sphere of epithelial follicular cells that produce glycoprotein thyroglobulin Butterfly-shaped gland in anterior neck on the trachea, just inferior to larynx, that consists of:

69. Thyroid Gland Location and Structure Colloid: fluid of follicle lumen containing thyroglobulin plus iodine; precursor to thyroid hormone Parafollicular cells: produce hormone calcitonin Butterfly-shaped gland in anterior neck on the trachea, just inferior to larynx, that consists of:

70. Location and Structure PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46700.html, CC BY 4.0, cropped Parafollicular cell Colloid-containing follicle Follicle cells (cuboidal epithelium)

71. Thyroid Hormone (TH) T4 (thyroxine) T3 (triiodothyronine) Both are iodine-containing amine hormones.

72. Thyroid Hormone (TH) Target cell T4 T3 T3 T3 T3 Gene transcription Increases basal metabolic rate and heat production calorigenic DNA Receptor

73. Thyroid Hormone (TH) Regulates tissue growth and development Maintains blood pressure Critical for normal skeletal and nervous system development and reproductive capabilities Increases adrenergic receptors in blood vessels

74. Synthesis of Thyroid Hormone (TH) Follicular cell Colloid Blood vessel

75. Iodide Thyroglobulin Lumen Iodine (oxidized iodide) MIT DIT T4 T3 Lysosome T4 T3 Golgi apparatus Synthesis of Thyroid Hormone (TH) Bloodstream ER Thyroxine-binding globulins (TBGs) Tyrosine (part of thyroglobulin)

76. T4 and T3 are transported by thyroxine-binding globulins (TBGs). • Both bind to target receptors, but T3 is 10 times more active than T4. • Peripheral tissues have enzymes needed to convert T4 to T3. • Enzymes remove one iodine atom from thyroxine. Thyroid Hormone (TH) Transport and Regulation

77. Negative Feedback Control Hypothalamus Anterior pituitary Thyroid gland TSH T3 + T4 ↑ TH levels GHIH Dopamine ↑ Cortisol ↑ Iodide ↓ TH levels TRH + + + + +

78. • Produced by parafollicular (C) cells in response to high Ca2+ levels • Antagonist to parathyroid hormone (PTH) Calcitonin Parafollicular cell Colloid-containing follicle Follicle cells (cuboidal epithelium)

79. No known physiological role in humans at normal physiological levels, but at higher-than-normal doses: • Inhibits osteoclast activity and prevents release of Ca2+ from bone matrix • Stimulates Ca2+ uptake and incorporation into bone matrix Calcitonin Parafollicular cell Colloid-containing follicle Follicle cells (cuboidal epithelium)

80. Calcitonin Thyroid gland Intestine Bone Kidney Blood vessel Ca2+ Calcitonin Inhibits Ca2+ reabsorption in the kidney (excreted in the urine) Promotes deposition of Ca2+ into bones (inhibits osteoblasts and stimulates osteoclasts) Lowers Ca2+ levels in the blood Inhibits Ca2+ absorption by the intestines

81. Parathyroid Gland

82. • 4 - 8 tiny yellow-brown glands embedded in a posterior surface of the thyroid. • Contain oxyphil cells (function not clear) and parathyroid cells, which secrete parathyroid hormone (PTH), or parathormone Parathyroid Gland Hyoid bone Thyroid cartilage Cricoid cartilage Right parathyroid glands Left parathyroid glands

83. • 4 - 8 tiny yellow-brown glands embedded in the posterior aspect of thyroid • Contain oxyphil cells (function not clear) and parathyroid cells, which secrete parathyroid hormone (PTH) Parathyroid Gland Oxyphil cells Blood vessel Parathyroid (chief) cell

84. • PTH is the most important hormone in Ca2+ homeostasis • Secreted in response to low blood levels of Ca2+ • Inhibited by rising levels of Ca2+ • Target organs: skeleton, kidneys, and intestine Parathyroid Hormone (PTH) Oxyphil cells Blood vessel Parathyroid (chief) cell

85. Parathyroid Hormone (PTH) Parathyroid glands (located on the back of the thyroid gland) Intestine Bone Kidney Blood vessel Ca2+ Ca2+ Ca2+ Rising levels of Ca2+ Low blood levels of Ca2+ PTH Vitamin D PTH + +

86. Functions of Parathyroid Hormone (PTH) Parathyroid glands (located on the back of the thyroid gland) Intestine Bone Kidney Blood vessel Ca2+ Ca2+ Ca2+ PTH Vitamin D PTH

87. Adrenal Gland

88. Adrenal Gland Adrenal gland Adrenal cortex 3 layers of glandular tissue that synthesize and secrete several different hormones Nervous tissue that is part of sympathetic nervous system Paired, pyramid-shaped organs atop kidneys (suprarenal glands) Adrenal medulla Superior surface of kidney

89. • Produces over 24 different hormones collectively called corticosteroids. • Steroid hormones are not stored in cells. • The rate of release depends on the rate of synthesis. Adrenal Cortex Adrenal gland Superior surface of kidney Adrenal cortex Adrenal medulla

90. Adrenal Cortex PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46684.html, CC BY 4.0, cropped Adrenal medulla Three layers of cortical cells produce different corticosteroids. Zona glomerulosa Mineralocorticoids Zona fasciculata Glucocorticoids Zona reticularis Gonadocorticoids

91. Adrenal Cortex Mineralocorticoids K+ (potassium) • Sets resting membrane potential of cells Na+ (sodium) • Affects ECF volume, blood volume, blood pressure, and levels of other ions (K+, H+, HCO3 , and Cl ) Function: regulate electrolyte concentrations in ECF primarily Na+ (sodium) and K+ (potassium)

92. Adrenal Cortex Mineralocorticoids Aldosterone ↑ Na+ reabsorption ↑ K+ elimination by kidneys Results in increased blood volume and blood pressure

93. Effects of aldosterone are short-lived. It stimulates synthesis and activation of Na+/K+ ATPase transport pumps, where Na+ is exchanged for K+. Adrenal Cortex Mineralocorticoids

94. Adrenal Cortex Mineralocorticoids Aldosterone NKA 3 Na+ 2 K+ Aldosterone effects within the cell Synthesis and activation of the ATPase Sodium-potassium pump

95. Aldosterone Secretion Renin- angiotensin- aldosterone mechanism Plasma concentration of K+ ACTH Atrial natriuretic peptide Factors that regulate aldosterone secretion:

96. Factors that Regulate Aldosterone Secretion: RAAM ↓ Blood pressure Renin Angiotensinogen (plasma protein) Angiotensin II ↑ Aldosterone secretion Release Cleaves off parts of Triggers cascade

97. Factors that Regulate Aldosterone Secretion ↑ Aldosterone secretion ↑ Aldosterone secretion ACTH ↓ Aldosterone secretion High blood pressure ↑ K+ plasma concentration

98. Adrenal Cortex Glucocorticoids Glucocorticoids Maintain blood pressure by increasing action of vasoconstrictors Keep blood glucose levels constant Influence metabolism of most cells and help us resist stressors

99. Adrenal Cortex Glucocorticoids Glucocorticoids Cortisol (hydrocortisone) Corticosterone Cortisone Only glucocorticoid in significant amounts in humans

100. Adrenal Cortex Regulation of Secretion CRH ACTH Stress Metabolic effects Cortisol HPA axis Anterior pituitary Hypothalamus Adrenal gland Kidney + + + + + +

101. Adrenal Cortex Actions of Cortisol Formation of glucose from fats and proteins Rise in blood pressure Enhances vasoconstriction Gluconeogenesis Metabolic effects Cortisol

102. Adrenal Cortex Actions of Cortisol • Depress cartilage and bone formation • Inhibit inflammation by decreasing release of inflammatory chemicals • Depress immune system • Disrupt normal cardiovascular, neural, and gastrointestinal functions Excessive levels of glucocorticoids

103. Glucocorticoid drugs can control symptoms of many inflammatory diseases (arthritis, allergies) but can also cause undesirable effects. Adrenal Cortex Actions of Cortisol

104. Adrenal Cortex Gonadocorticoids Adrenal cortex Weak androgens (male sex hormones) are converted to testosterone in tissue cells, some to estrogens. May contribute to: • Onset of puberty and appearance of secondary sex characteristics • Sex drive in women • Source of estrogens in postmenopausal women

105. Medullary chromaffin cells synthesize catecholamines: epinephrine (80%) and norepinephrine (20%) Adrenal Medulla Effects of catecholamines • Vasoconstriction • Increased heart rate • Increased blood glucose levels • Blood diverted to brain, heart, and skeletal muscle 20% 80%

106. Adrenal Medulla © by Lecturio Both hormones have basically same effects, but: Epinephrine is more a stimulator of metabolic activities (Example: bronchial dilation, and blood flow to skeletal muscles and heart). Norepinephrine has more of an influence on peripheral vasoconstriction and blood pressure. Responses to stressors are brief, unlike adrenal cortical hormones. Adrenal medulla

107. Pineal Gland

108. The pineal gland is a small gland that is hanging from the roof of the third ventricle. Pinealocytes secrete melatonin, derived from serotonin. Pineal Gland

109. Pineal Gland Pineal gland Pinealocytes secrete melatonin. Third ventricle

110. Pineal Gland Day/night cycles Timing of sexual maturation and puberty Production of antioxidant and detoxification molecules in cells Physiological processes that show rhythmic variations (body temperature, sleep, appetite) Melatonin may affect:

111. Other Endocrine Organs

112. The pancreas is a triangular gland located partially behind the stomach. It has both exocrine and endocrine cells. Other Endocrine Organs Pancreas

113. Other Endocrine Organs Pancreas © by Lecturio Lobules Head Body Tail Pancreatic duct Common bile duct Duodenal papilla

114. Pancreas Acinar cells (exocrine) produce enzyme-rich juice for digestion Pancreatic islets (islets of Langerhans) contain endocrine cells Alpha () cells Beta () cells Produce glucagon (hyperglycemic hormone) Produce insulin (hypoglycemic hormone)

115. Pancreatic Islets PhilSchatz, Anatomie, https://philschatz.com/anatomy-book/contents/m46685.html, CC BY 4.0, cropped The alpha and beta cells appear as little islands among the acinar cells. Alpha cells Beta cells Exocrine acinus

116. Extremely potent hyperglycemic agent • Triggered by decreased blood glucose levels, rising amino acid levels, or sympathetic nervous system Pancreatic Islets Glucagon PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46685.html, CC BY 4.0, edited Splenic artery Glucagon release: alpha cells of pancreas release glucagon

117. Raises blood glucose levels by targeting liver to: • Break down glycogen into glucose (glycogenolysis) • Synthesize glucose from lactic acid and other noncarbohydrates (gluconeogenesis) • Release glucose into the blood Pancreatic Islets Glucagon PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46685.html, CC BY 4.0, edited Glucagon release: alpha cells of pancreas release glucagon Splenic artery

118. Pancreatic Islets Glucagon Beta cell Glucagon Hypoglycemia, GIP, amino acids Alpha cell Brain • Food intake ↓ • Appetite ↓ • Satiety ↑ Pancreas • Insulin secretion ↑ Liver • Glucose production ↑ • Glucose breakdown ↓ • Lipid breakdown ↑ • Lipid production ↓ • Ketone body production ↑ • Amino acid breakdown ↓ Brown adipose tissue • Resting energy expenditure ↑ Heart • Heart rate (↑) • Contractility (↑)

119. • Secreted when blood glucose levels increase • Synthesized as proinsulin that is then modified Pancreatic Islets Insulin PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46685.html, CC BY 4.0, edited Splenic artery Insulin release: beta cells of pancreas release insulin

120. Pancreatic Islets Insulin Beta cell Insulin Enhances membrane transport of glucose into fat and muscle cells Inhibits conversion of amino acids or fats to glucose Smooth ER Rough ER Inhibits breakdown of glycogen to glucose Liver Mitochondria

121. Pancreatic Islets Insulin Beta cell Insulin Plays a role in neuronal development, learning, and memory Binding to tyrosine kinase enzyme receptor triggers cell to increase glucose uptake

122. Insulin also triggers cells to: • Catalyze oxidation of glucose for ATP production: first priority • Polymerize glucose to form glycogen • Convert glucose to fat (particularly in adipose tissue) Pancreatic Islets Insulin PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46685.html, CC BY 4.0, edited Insulin release: beta cells of pancreas release insulin Splenic artery

123. Pancreatic Islets Insulin Beta cell Insulin Catalyze oxidation of glucose for ATP production: first priority Convert glucose to fat (particularly in adipose tissue) Polymerize glucose to form glycogen

124. Pancreatic Islets Insulin Factors that influence insulin release Elevated blood glucose levels: primary stimulus Rising blood levels of amino acids and fatty acids Hormones glucagon, epinephrine, growth hormone, thyroxine, glucocorticoids Somatostatin and sympathetic nervous system inhibit insulin release Release of acetylcholine by parasympathetic nerve fibers

125. The Gonads and Placenta • Maturation of reproductive organs • Appearance of secondary sexual characteristics • With progesterone, causes breast development and cyclic changes in uterine mucosa • Initiates maturation of male reproductive organs • Causes appearance of male secondary sexual characteristics and sex drive • Necessary for normal sperm production • Maintains reproductive organs in functional state Progesterone Testosterone Estrogen Estrogen Progesterone Gonads Ovaries (female) Testes (male)

126. The Placenta secretes estrogens, progesterone, and human chorionic gonadotropin (hCG) Placenta

127. Most endocrine organs operate well until old age, however: • ↓ GH (muscle atrophy) • ↓ TH (lower basal metabolic rates) • = PTH (lack of estrogen in older women makes them more vulnerable to bone-demineralizing effects of PTH) • ↓ Glucose tolerance • Ovaries: become unresponsive to gonadotropins (estrogen deficiency) • ↓ Testosterone (effect is not usually seen until very old age) Endocrine Function throughout Life

128. In a Nutshell  The endocrine system acts with the nervous system. It coordinates and integrates the activity of body cells.  Hormones act by binding to specific target cells and altering cell activity.  There are several endocrine glands throughout the body, which secrete specific hormones and target specific cells.

129. In a Nutshell  The pituitary gland secretes 8 different hormones: 2 posterior pituitary hormones and 6 anterior pituitary hormones.  The thyroid gland secretes thyroid hormone (metabolic regulator).  The parathyroid secretes parathyroid hormone (Ca2+ levels).

130. In a Nutshell  The adrenal gland secretes hormones responsible for several different body activities (regulation of blood pressure and stress response).  The pineal gland secretes the hormone melatonin (circadian rhythm).  Other organs in the body with endocrine function include the pancreas, gonads, and placenta.

12.0 The Endocrine System.pdf

12.0 The Endocrine System.pdf

Recomendados

Más contenido relacionado

Similar a 12.0 The Endocrine System.pdf

Similar a 12.0 The Endocrine System.pdf(20)

Más de RexBlancoNuez

Más de RexBlancoNuez(9)

Último

Último(20)

12.0 The Endocrine System.pdf