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Chapter 18: The Endocrine System What is the importance of intercellular communication?

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1 Chapter 18: The Endocrine System What is the importance of intercellular communication?

2 Endocrine System Regulates long-term processes: ◦ growth ◦ development ◦ reproduction

3 Endocrine System Uses chemical messengers to relay information and instructions between cells

4 What are the modes of intercellular communication used by the endocrine and nervous systems?

5 Direct Communication Exchange of ions and molecules between adjacent cells across gap junctions Occurs between 2 cells of same type Highly specialized and relatively rare

6 Paracrine Communication Uses chemical signals to transfer information from cell to cell within single tissue Most common form of intercellular communication

7 Endocrine Communication Endocrine cells release chemicals (hormones) into bloodstream Alters metabolic activities of many tissues and organs simultaneously

8 Target Cells Are specific cells that possess receptors needed to bind and “read” hormonal messages

9 What is the functional significance of the differences between the two systems?

10 Endocrine System Is unable to handle split-second responses

11 Nervous System Handles crisis management

12 Synaptic Communication Releases neurotransmitter at a synapse that is very close to target cells Ideal for crisis management

13 Mechanisms of Intercellular Communication Table 18–1

14 Endocrine and Nervous Systems Are similarly organized: ◦ rely on release of chemicals ◦ share many chemical messengers ◦ are regulated primarily by negative feedback ◦ share a common goal: to preserve homeostasis

15 How do the cellular components of the endocrine system compare with those of other tissues and systems?

16 Endocrine System Includes all endocrine cells and body tissues that produce hormones or paracrine factors

17 Endocrine Cells Glandular secretory cells that release their secretions into extracellular fluid

18 Exocrine Cells Secrete their products onto epithelial surfaces

19 Figure 18–1 Endocrine System

20 What are the major structural classes of hormones?

21 Hormones Can be divided into 3 groups: ◦ amino acid derivatives ◦ peptide hormones ◦ lipid derivatives

22 Figure 18–2 Classes of Hormones

23 Amino Acid Derivatives Small molecules structurally related to amino acids Synthesized from the amino acids tyrosine and tryptophan

24 Tyrosine Derivatives Thyroid hormones Compounds: ◦ epinephrine (E) ◦ norepinephrine (NE) ◦ dopamine, also called catecholamines

25 Tryptophan Derivative Melatonin: ◦ produced by pineal gland

26 Peptide Hormones Chains of amino acids Synthesized as prohormones: ◦ inactive molecules converted to active hormones before or after secretion

27 2 Groups of Peptide Hormones Group 1: ◦ glycoproteins:  more than 200 amino acids long, with carbohydrate side chains:  thyroid-stimulating hormone (TSH)  luteinizing hormone (LH)  follicle-stimulating hormone (FSH)

28 2 Groups of Peptide Hormones Group 2: ◦ all hormones secreted by:  hypothalamus  heart  thymus  digestive tract  pancreas  posterior lobe of pituitary gland  anterior lobe of pituitary gland

29 2 Classes of Lipid Derivatives Eicosanoids: ◦ derived from arachidonic acid Steroid hormones: ◦ derived from cholesterol

30 Eicosanoids Are small molecules with five-carbon ring at one end Are important paracrine factors Coordinate cellular activities Affect enzymatic processes in extracellular fluids

31 Leukotrienes Are eicosanoids released by activated white blood cells, or leukocytes Important in coordinating tissue responses to injury or disease

32 Prostaglandins A second group of eicosanoids produced in most tissues of body Are involved in coordinating local cellular activities Sometimes converted to thromboxanes and prostacyclins

33 Steroid Hormones Are lipids structurally similar to cholesterol Released by: ◦ reproductive organs (androgens by testes, estrogens, and progestins by ovaries) ◦ adrenal glands (corticosteroids) ◦ kidneys (calcitriol)

34 Steroid Hormones Remain in circulation longer than peptide hormones Are absorbed gradually by liver Are converted to soluble form Are excreted in bile or urine

35 Hormones Circulate freely or bound to transport proteins

36 Free Hormones Remain functional for less than 1 hour: ◦ diffuse out of bloodstream:  bind to receptors on target cells ◦ are absorbed:  broken down by cells of liver or kidney ◦ are broken down by enzymes:  in plasma or interstitial fluids

37 Thyroid and Steroid Hormones Remain in circulation much longer Enter bloodstream: ◦ more than 99% become attached to special transport proteins

38 Bloodstream Contains substantial reserve of bound hormones

39 What are the general mechanisms of hormonal action?

40 Hormone Receptor Is a protein molecule to which a particular molecule binds strongly Responds to several different hormones

41 Cells Different tissues have different combinations of receptors Presence or absence of specific receptor determines hormonal sensitivity

42 Catecholamines and Peptide Hormones Are not lipid soluble Unable to penetrate cell membrane Bind to receptor proteins at outer surface of cell membrane (extracellular receptors)

43 Eicosanoids Are lipid soluble Diffuse across membrane to reach receptor proteins on inner surface of membrane (intracellular receptors)

44 Hormone Binds to receptors in cell membrane Cannot have direct effect on activities inside target cell Uses intracellular intermediary to exert effects

45 Intracellular Intermediaries First messenger: ◦ leads to second messenger ◦ may act as enzyme activator, inhibitor, or cofactor ◦ results in change in rates of metabolic reactions

46 Important Second Messengers Cyclic-AMP (cAMP): ◦ derivative of ATP Cyclic-GMP (cGMP): ◦ derivative of GTP Calcium ions

47 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

48 Receptor Cascade A single hormone promotes release of more than 1 type of second messenger

49 Down-regulation Presence of a hormone triggers decrease in number of hormone receptors When levels of particular hormone are high, cells become less sensitive

50 Up-regulation Absence of a hormone triggers increase in number of hormone receptors When levels of particular hormone are low, cells become more sensitive

51 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

52 Figure 18–3 G Proteins and Hormone Activity

53 G Protein Changes concentration of second messenger cyclic-AMP (cAMP) within cell Increased cAMP level accelerates metabolic activity within cell

54 Increased cAMP Levels (1 of 2) 1. Activated G protein: ◦ activates enzyme adenylate cyclase 2. Adenylate cyclase: ◦ converts ATP to cyclic-AMP

55 Increased cAMP Levels (2 of 2) 3. Cyclic-AMP (second messenger): ◦ activates kinase 4. Activated kinases affect target cell: ◦ depends on nature of proteins affected

56 Figure 18–3 G Proteins and Hormone Activity

57 Lower cAMP Levels 1. Activated G protein stimulates PDE activity 2. Inhibits adenylate cyclase activity 3. Levels of cAMP decline 4. cAMP breakdown accelerates; cAMP synthesis is prevented

58 Figure 18–3 G Proteins and Hormone Activity

59 G Proteins and Calcium Ions (1 of 2) Activated G proteins trigger: ◦ opening of calcium ion channels in membrane ◦ release of calcium ions from intracellular stores

60 G Proteins and Calcium Ions (2 of 2) 1. G protein activates enzyme phospholipase C (PLC) 2. Enzyme triggers receptor cascade: ◦ production of diacylglycerol (DAG) and inositol triphosphate (IP 3 ) from membrane phospholipids

61 Steroid Hormones Cross cell membrane Bind to receptors in cytoplasm or nucleus, activating or inactivating specific genes

62 Figure 18–4a Steroid Hormones

63 Alter rate of DNA transcription in nucleus: ◦ change patterns of protein synthesis Directly affect metabolic activity and structure of target cell

64 Thyroid Hormones Figure 18–4b

65 Thyroid Hormones Cross cell membrane: ◦ primarily by transport mechanism Bind to receptors in nucleus and on mitochondria: ◦ activating specific genes ◦ changing rate of transcription

66 KEY CONCEPT (1 of 2) Hormones coordinate cell, tissue, and organ activities Circulate in extracellular fluid and bind to specific receptors

67 KEY CONCEPT (2 of 2) Hormones modify cellular activities by: ◦ altering membrane permeability ◦ activating or inactivating key enzymes ◦ changing genetic activity

68 How are endocrine organs controlled?

69 Endocrine Reflexes Functional counterparts of neural reflexes In most cases, controlled by negative feedback mechanisms

70 Endocrine Reflex Triggers Humoral stimuli: ◦ changes in composition of extracellular fluid Hormonal stimuli: ◦ arrival or removal of specific hormone Neural stimuli: ◦ arrival of neurotransmitters at neuroglandular junctions

71 Simple Endocrine Reflex Involves only 1 hormone Controls hormone secretion by: ◦ heart ◦ pancreas ◦ parathyroid gland ◦ digestive tract

72 Complex Endocrine Reflex Involves: ◦ 1 or more intermediary steps ◦ 2 or more hormones

73 Figure 18–5 Hypothalamus

74 Hypothalamus (1 of 2) Integrates activities of nervous and endocrine systems in 3 ways: 1. Secretes regulatory hormones: ◦ special hormones control endocrine cells in pituitary gland

75 Hypothalamus (2 of 2) 2. Acts as an endocrine organ 3. Contains autonomic centers: ◦ exert direct neural control over endocrine cells of adrenal medullae

76 Neuroendocrine Reflexes Pathways include both neural and endocrine components

77 Complex Commands Issued by changing: ◦ amount of hormone secreted ◦ pattern of hormone release

78 Pulses Hypothalamic and pituitary hormones released in sudden bursts Frequency varies response of target cells

79 Where is the pituitary gland located, and what is its relationship to the hypothalamus?

80 Figure 18–6 Pituitary Gland

81 Pituitary Gland Pituitary Gland Also called hypophysis Lies within sella turcica Hangs inferior to hypothalamus: ◦ connected by infundibulum

82 Diaphragma Sellae Locks pituitary in position Isolates it from cranial cavity

83 Pituitary Gland Releases 9 important peptide hormones Hormones bind to membrane receptors: ◦ use cAMP as second messenger

84 Anterior Lobe Also called adenohypophysis: 1.pars distalis 2.pars intermedia 3.pars tuberalis

85 Figure 18–6 Anterior Lobe

86 Median Eminence Swelling near attachment of infundibulum Where hypothalamic neurons release regulatory factors: ◦ into interstitial fluids ◦ through fenestrated capillaries

87 Figure 18–7 Median Eminence

88 Portal Vessels Blood vessels link 2 capillary networks Entire complex is portal system

89 Hypophyseal Portal System Ensures that regulatory factors reach intended target cells before entering general circulation

90 What are the hormones produced by the anterior lobe, and what are the functions of those hormones?

91 2 Classes of Hypothalamic Regulatory Hormones 1. Releasing hormones 2. Inhibiting hormones

92 Figure 18–8a Hypothalamic Regulatory Hormones Rate of secretion is controlled by negative feedback

93 Figure 18–8b Hypothalamic Regulatory Hormones

94 Releasing Hormones (RH) Stimulate synthesis and secretion of 1 or more hormones at anterior lobe

95 Inhibiting Hormones (IH) Prevent synthesis and secretion of hormones from anterior lobe

96 Figure 18–8a Anterior Lobe Hormones “turn on” endocrine glands or support other organs

97 Thyroid-Stimulating Hormone (TSH) Also called thyrotropin Triggers release of thyroid hormones

98 Adrenocorticotropic Hormone (ACTH) Also called corticotropin Stimulates release of steroid hormones by adrenal cortex Targets cells that produce glucocorticoids

99 Gonadotropins Regulate activities of gonads (testes, ovaries) Follicle-stimulating hormone Luteinizing hormone

100 Follicle-Stimulating Hormone (FSH) (1 of 2) Also called follitropin Stimulates follicle development and estrogen secretion in females

101 Follicle-Stimulating Hormone (FSH) (2 of 2) Stimulates sustentacular cells in males: ◦ promotes physical maturation of sperm Production inhibited by inhibin: ◦ peptide hormone released by testes and ovaries

102 Luteinizing Hormone (LH) Also called lutropin Causes ovulation and progestin production in females Causes androgen production in males

103 FSH and LH Production Stimulated by gonadotropin-releasing hormone (GnRH) from hypothalamus: ◦ GnRH production inhibited by estrogens, progestins, and androgens

104 Prolactin (PRL) Also called mammotropin Stimulates development of mammary glands and milk production Production inhibited by prolactin- inhibiting hormone (PIH)

105 Prolactin (PRL) Stimulates PIH release Inhibits secretion of prolactin-releasing factors (PRF)

106 Figure 18–8b Prolactin (PRL)

107 Growth Hormone (GH) Also called somatotropin Stimulates cell growth and replication Production regulated by: ◦ growth hormone–releasing hormone (GH– RH) ◦ growth hormone–inhibiting hormone (GH– IH)

108 Melanocyte-Stimulating Hormone (MSH) Also called melanotropin Stimulates melanocytes to produce melanin Inhibited by dopamine

109 Melanocyte-Stimulating Hormone (MSH) Secreted by pars intermedia during: ◦ fetal development ◦ early childhood ◦ pregnancy ◦ certain diseases

110 KEY CONCEPT (1 of 4) Hypothalamus produces regulatory factors that adjust activities of anterior lobe of pituitary gland, which produces 7 hormones

111 KEY CONCEPT (2 of 4) Most hormones control other endocrine organs, including thyroid gland, adrenal gland, and gonads

112 KEY CONCEPT (3 of 4) Anterior lobe produces growth hormone, which stimulates cell growth and protein synthesis

113 KEY CONCEPT (4 of 4) Posterior lobe of pituitary gland releases 2 hormones produced in hypothalamus: ◦ ADH restricts water loss and promotes thirst ◦ oxytocin stimulates smooth muscle contractions in:  mammary glands  uterus  prostate gland

114 What hormones are produced by the posterior lobe, and what are their functions?

115 Posterior Lobe Also called neurohypophysis Contains unmyelinated axons of hypothalamic neurons Supraoptic and paraventricular nuclei manufacture: ◦ antidiuretic hormone (ADH) ◦ oxytocin (OT)

116 Antidiuretic Hormone Decreases amount of water lost at kidneys Elevates blood pressure Release inhibited by alcohol

117 Oxytocin Stimulates contractile cells in mammary glands Stimulates smooth muscles in uterus Secretion and milk ejection are part of neuroendocrine reflex

118 Table 18–2 Summary: The Hormones of the Pituitary Gland

119 What are the results of abnormal levels of pituitary hormone production?

120 Hypogonadism Low production of gonadotropins In children: ◦ will not undergo sexual maturation In adults: ◦ cannot produce functional sperm or oocytes

121 Diabetogenic Effect Elevation of blood glucose levels by GH

122 Diabetes Insipidus Inadequate amounts of ADH released from posterior lobe Impairs water conservation at kidneys

123 Where is the thyroid gland located, and what is its structure?

124 Thyroid Gland Lies anterior to thyroid cartilage of larynx Consists of 2 lobes connected by narrow isthmus

125 Thyroid Gland Figure 18–10a, b

126 Thyroid Follicles Hollow spheres lined by cuboidal epithelium Cells surround follicle cavity that contains viscous colloid

127 Thyroid Follicles Surrounded by network of capillaries that: ◦ deliver nutrients and regulatory hormones ◦ accept secretory products and metabolic wastes

128 Thyroid Follicles Figure 18–11a, b

129 Thyroglobulin Globular protein Synthesized by follicle cells Secreted into colloid of thyroid follicles Molecules contain amino acid tyrosine

130 Figure 18–10c Thyroglobulin

131 What hormones are produced by the thyroid gland?

132 Thyroxine (T 4 ) Also called tetraiodothyronine Contains 4 iodide ions

133 Triiodothyronine (T 3 ) Contains 3 iodide ions

134 Rate of Thyroid Hormone Release Major factor: ◦ TSH concentration in circulating blood Figure 18–11b

135 Thyroid-Binding Globulins (TBGs) Transport proteins Attach to most T 4 and T 3 molecules

136 Transthyretin Also called thyroid-binding prealbumin (TBPA) Is a transport protein Attaches to most remaining T 4 and T 3 molecules

137 Unbound Thyroid Hormones Diffuse out of bloodstream and into other tissues Disturb equilibrium Carrier proteins release more thyroid hormones until new equilibrium is reached

138 Thyroid-Stimulating Hormone (TSH) Absence causes thyroid follicles to become inactive: ◦ neither synthesis nor secretion occur Binds to membrane receptors Activates key enzymes in thyroid hormone production

139 What are the functions of thyroid hormones, and what are the results of abnormal levels of thyroid hormones?

140 Thyroid Hormones Enter target cells by transport system Affect most cells in body Bind to receptors in: ◦ cytoplasm ◦ surfaces of mitochondria ◦ nucleus

141 Calorigenic Effect Cell consumes more energy resulting in increased heat generation

142 Thyroid Hormones In children, essential to normal development of: ◦ skeletal, muscular, and nervous systems

143 Thyroid Gland Is responsible for strong, immediate, and short-lived increase in rate of cellular metabolism

144 Thyroid Gland Table 18–3

145 Iodide Ions Are actively transported into thyroid follicle cells: ◦ stimulated by TSH Reserves in thyroid follicles Excess removed from blood at kidneys Deficiency limits rate of thyroid hormone production

146 C (Clear) Cells Produce calcitonin (CT): ◦ helps regulate concentrations of Ca 2+ in body fluids

147 Where are the parathyroid glands?

148 Parathyroid Glands Embedded in posterior surface of thyroid gland Figure 18–12

149 What is the function of the hormone produced by the parathyroid glands?

150 Parathyroid Hormone (PTH) Produced by chief cells In response to low concentrations of Ca 2+

151 4 Effects of PTH 1. It stimulates osteoclasts: ◦ accelerates mineral turnover ◦ releases Ca 2+ from bone 2. It inhibits osteoblasts: ◦ reduces rate of calcium deposition in bone

152 4 Effects of PTH 3. It enhances reabsorption of Ca 2+ at kidneys, reducing urinary loss 4. It stimulates formation and secretion of calcitriol at kidneys

153 Calcitriol Effects complement or enhance PTH Enhances Ca 2+, PO 4 3— absorption by digestive tract

154 Parathyroid Glands Primary regulators of blood calcium I levels in adults Figure 18–13

155 Parathyroid Glands Table 18–4

156 KEY CONCEPT Thyroid gland produces: ◦ hormones that adjust tissue metabolic rates ◦ a hormone that usually plays minor role in calcium ion homeostasis by opposing action of parathyroid hormone

157 What are the location, structure, and general functions of the adrenal gland?

158 Adrenal Glands Lie along superior border of each kidney Subdivided into superficial adrenal cortex and an inner adrenal medulla

159 Adrenal Glands Figure 18–14

160 Adrenal Cortex Stores lipids, especially cholesterol and fatty acids Manufactures steroid hormones: ◦ adrenocortical steroids (corticosteroids)

161 Adrenal Cortex Subdivided into 3 regions: 1.zona glomerulosa 2.zona fasciculate 3.zona reticularis

162 Adrenal Cortex Table 18–5

163 What hormones are produced by the adrenal glands, and what are their functions?

164 Zona Glomerulosa Outer region of adrenal cortex Produces mineralocorticoids: ◦ e.g., aldosterone

165 Aldosterone Stimulates: ◦ conservation of sodium ions ◦ elimination of potassium ions Increases sensitivity of salt receptors in taste buds

166 Aldosterone Secretion responds to: ◦ drop in blood Na +, blood volume, or blood pressure ◦ rise in blood K + concentration

167 Zona Fasciculata Produces glucocorticoids Endocrine cells are larger and contain more lipids than zona glomerulosa

168 Zona Fasciculata Secretes cortisol (hydrocortisone) with corticosterone: ◦ liver converts cortisol to cortisone

169 Glucocorticoids Secretion regulated by negative feedback Have inhibitory effect on production of: ◦ corticotropin-releasing hormone (CRH) in hypothalamus ◦ ACTH in anterior lobe

170 Glucocorticoids Accelerate glucose synthesis and glycogen formation Show anti-inflammatory effects: ◦ inhibit activities of white blood cells and other components of immune system

171 Zona Reticularis Network of endocrine cells Forms narrow band bordering each adrenal medulla Produces androgens under stimulation by ACTH

172 Adrenal Medullae Secretory activities controlled by sympathetic division of ANS Produces epinephrine (adrenaline) and norepinephrine Metabolic changes persist for several minutes

173 KEY CONCEPT Adrenal glands produce hormones that adjust metabolic activities at specific sites Affects either pattern of nutrient utilization, mineral ion balance, or rate of energy consumption by active tissues

174 Where is the pineal gland, and what are the functions of the hormone it produces?

175 Pineal Gland Lies in posterior portion of roof of third ventricle Contains pinealocytes: ◦ synthesize hormone melatonin

176 Functions of Melatonin Inhibiting reproductive functions Protecting against damage by free radicals Setting circadian rhythms

177 Where is the pancreas, and what is its structure?

178 Pancreas Lies between: ◦ inferior border of stomach ◦ and proximal portion of small intestine Contains exocrine and endocrine cells

179 Figure 18–15 Pancreas

180 Endocrine Pancreas Cells form clusters: ◦ pancreatic islets, or islets of Langerhans

181 What hormones are produced by the pancreas, and what are their functions?

182 4 Types of Cells in Pancreatic Islets Alpha cells: ◦ produce glucagon Beta cells: ◦ secrete insulin

183 4 Types of Cells in Pancreatic Islets Delta cells: ◦ produce peptide hormone identical to GH-IH F cells: ◦ secrete pancreatic polypeptide (PP)

184 Pancreatic Islets Figure 18–16

185 Table 18–6 Pancreatic Islets

186 Blood Glucose Levels When levels rise: ◦ beta cells secrete insulin, stimulates transport of glucose across cell membranes When levels decline: ◦ alpha cells secrete glucagons, stimulates glucose release by liver

187 Insulin Is a peptide hormone released by beta cells Affects target cells

188 5 Effects of Insulin 1. Accelerates glucose uptake 2. Accelerates glucose utilization and enhanced ATP production 3. Stimulates glycogen formation 4. Stimulates amino acid absorption and protein synthesis 5. Stimulates triglyceride formation in adipose tissue

189 Glucagons Released by alpha cells Mobilize energy reserves Affects target cells

190 3 Effects of Glucagons 1. Stimulates breakdown of glycogen in skeletal muscle and liver cells 2. Stimulates breakdown of triglycerides in adipose tissue 3. Stimulates production of glucose in liver

191 KEY CONCEPT (1 of 3) Pancreatic islets release insulin and glucagons

192 KEY CONCEPT (2 of 3) Insulin is released when blood glucose levels rise Stimulates glucose transport into, and utilization by, peripheral tissues

193 KEY CONCEPT (3 of 3) Glucagon released when blood glucose levels decline Stimulates glycogen breakdown, glucose synthesis, and fatty acid release

194 What are the functions of hormones produced by the kidneys, heart, thymus, testes, ovaries, and adipose tissue?

195 Hormones Produced by Specific Organs Table 18–7

196 Intestines Produce hormones important to coordination of digestive activities

197 Kidneys Produce the hormones calcitriol and erythropoietin Produce the enzyme renin

198 Calcitriol Stimulates calcium and phosphate ion absorption along digestive tract Figure 18–17a

199 Effects of Calcitriol on Calcium Metabolism Stimulates formation and differentiation of osteoprogenitor cells and osteoclasts Stimulates bone resorption by osteoclasts

200 Effects of Calcitriol on Calcium Metabolism Stimulates Ca 2+ reabsorption at kidneys Suppresses parathyroid hormone (PTH) production

201 Erythropoietin (EPO) Stimulates red blood cell production by bone marrow: ◦ increased RBCs elevate blood volume

202 Renin Converts angiotensinogen to angiotensin I Angiotensin I is converted to angiotensin II

203 Angiotensin II 1. Stimulates adrenal production of aldosterone 2. Stimulates pituitary release of ADH 3. Promotes thirst 4. Elevates blood pressure

204 The Renin–Angiotensin System Figure 18–17b

205 Heart Produces natriuretic peptides (ANP and BNP): ◦ when blood volume becomes excessive

206 Natriuretic Peptide Action opposes angiotensin II Resulting in reduction in blood volume and blood pressure

207 Thymus Produces thymosin hormones: ◦ that helps develop and maintain normal immune defenses

208 Testes Produce androgens in interstitial cells: ◦ testosterone:  is most important male hormone Secrete inhibin in sustentacular cells: ◦ support differentiation and physical maturation of sperm

209 Ovaries Produce estrogens: ◦ principle estrogen is estradiol After ovulation, follicle cells: ◦ reorganize into corpus luteum ◦ release estrogens and progestins, especially progesterone

210 Adipose Tissue Secretions 1. Leptin: ◦ feedback control for appetite ◦ controls normal levels of GnRH, gonadotropin synthesis 2. Resistin: ◦ reduces insulin sensitivity

211 How do hormones interact to produce coordinated physiological responses?

212 Hormone Interactions 1. Antagonistic (opposing) effects 2. Synergistic (additive) effects 3. Permissive effects: ◦ 1 hormone is necessary for another to produce effect 4. Integrative effects: ◦ hormones produce different and complementary results

213 What hormones are of special importance to normal growth, and what are their roles?

214 Hormones Important to Growth 1. GH 2. Thyroid hormones 3. Insulin 4. PTH 5. Calcitriol 6. Reproductive hormones

215 Growth Hormone (GH) In children: ◦ supports muscular and skeletal development In adults: ◦ maintains normal blood glucose concentrations ◦ mobilizes lipid reserves

216 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

217 Insulin Allows passage of glucose and amino acids across cell membranes

218 Parathyroid Hormone (PTH) and Calcitriol Promote absorption of calcium salts for deposition in bone Inadequate levels causes weak and flexible bones

219 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

220 What is general adaptation syndrome?

221 General Adaptation Syndrome (GAS) Also called stress response How bodies respond to stress-causing factors Figure 18–18

222 General Adaptation Syndrome (GAS) Is divided into 3 phases: 1.alarm phase 2.resistance phase 3.exhaustion phase

223 Alarm Phase Is an immediate response to stress Is directed by ANS Energy reserves mobilized (glucose) “Fight or flight” responses Dominant hormone is epinephrine

224 7 Characteristics of Alarm Phase 1. Increased mental alertness 2. Increased energy consumption 3. Mobilization of energy reserves (glycogen and lipids)

225 7 Characteristics of Alarm Phase 4. Circulation changes: ◦ increased blood flow to skeletal muscles ◦ decreased blood flow to skin, kidneys, and digestive organs

226 7 Characteristics of Alarm Phase 5. Drastic reduction in digestion and urine production 6. Increased sweat gland secretion 7. Increases in blood pressure, heart rate, and respiratory rate

227 Resistance Phase Entered if stress lasts longer than few hours Dominant hormones are glucocorticoids Energy demands remain high Glycogen reserves nearly exhausted after several hours of stress

228 Effects of Resistance Phase 1. Mobilize remaining lipid and protein reserves 2. Conserve glucose for neural tissues 3. Elevate and stabilize blood glucose concentrations 4. Conserve salts, water, and loss of K +, H +

229 Exhaustion Phase Begins when homeostatic regulation breaks down Failure of 1 or more organ systems will prove fatal Mineral imbalance

230 What are the effects of hormones on behavior?

231 Hormone Changes Can alter intellectual capabilities, memory, learning, and emotional states Affect behavior when endocrine glands are oversecreting or undersecreting

232 Aging Causes few functional changes Decline in concentration of: ◦ growth hormone ◦ reproductive hormones

233 Endocrine System Provides long-term regulation and adjustments of homeostatic mechanisms: ◦ fluid and electrolyte balance ◦ cell and tissue metabolism ◦ growth and development ◦ reproductive functions ◦ assists nervous system response to stressful stimuli through general adaptation syndrome

234 Interactions between Endocrine and Other Systems Figure 18–19

235 Primary Disorders Problems within endocrine organ because of: ◦ metabolic factor ◦ physical damage ◦ congenital problems

236 Secondary Disorders Problems in other organs or target tissues Often involve hypothalamus or pituitary gland

237 SUMMARY (1 of 9) Paracrine communication Endocrine communication

238 SUMMARY (2 of 9) Classes of hormones: ◦ amino acid derivatives ◦ peptide hormones ◦ lipid derivatives, including steroid hormones and eicosanoids

239 SUMMARY (3 of 9) Secretion and distribution of hormones Endocrine reflexes Hypothalamus regulation of the endocrine system

240 SUMMARY (4 of 9) The pituitary gland: ◦ the anterior lobe ◦ the posterior lobe

241 SUMMARY (5 of 9) Releasing hormones Inhibiting hormones

242 SUMMARY (6 of 9) The thyroid gland: ◦ thyroid follicles ◦ thyroid hormones

243 SUMMARY (7 of 9) The parathyroid glands The adrenal glands: ◦ the adrenal cortex ◦ the adrenal medulla

244 SUMMARY (8 of 9) The pineal gland The pancreas: ◦ the pancreatic islets ◦ insulin and glucagons

245 SUMMARY (9 of 9) Endocrine tissues in other systems Hormonal interaction Role of hormones in growth Hormonal response to stress Effects of hormones on behavior Effects of aging on hormone production


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