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Chapter 18: The Endocrine System

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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

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 Endocrine System Figure 18–1

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 Classes of Hormones Figure 18–2

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
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
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 G Proteins and Hormone Activity
Figure 18–3

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)
Activated G protein: activates enzyme adenylate cyclase Adenylate cyclase: converts ATP to cyclic-AMP

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

56 G Proteins and Hormone Activity
Figure 18–3

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

58 G Proteins and Hormone Activity
Figure 18–3

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)
G protein activates enzyme phospholipase C (PLC) Enzyme triggers receptor cascade: production of diacylglycerol (DAG) and inositol triphosphate (IP3) from membrane phospholipids

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

62 Steroid Hormones Figure 18–4a

63 Steroid Hormones 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 Hypothalamus Figure 18–5

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

75 Hypothalamus (2 of 2) Acts as an endocrine organ
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 Pituitary Gland Figure 18–6

81 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: pars distalis
pars intermedia pars tuberalis

85 Anterior Lobe Figure 18–6

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

87 Median Eminence Figure 18–7

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
Releasing hormones Inhibiting hormones

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

93 Hypothalamic Regulatory Hormones
Figure 18–8b

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

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 Prolactin (PRL) Figure 18–8b

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

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

120 Hypogonadism Low production of gonadotropins In children: In adults:
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 Thyroglobulin Figure 18–10c

131 What hormones are produced by the thyroid gland?

132 Thyroxine (T4) Also called tetraiodothyronine Contains 4 iodide ions

133 Triiodothyronine (T3) 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 T4 and T3 molecules

136 Transthyretin Also called thyroid-binding prealbumin (TBPA)
Is a transport protein Attaches to most remaining T4 and T3 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 Ca2+ 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 Ca2+

151 4 Effects of PTH It stimulates osteoclasts: It inhibits osteoblasts:
accelerates mineral turnover releases Ca2+ from bone It inhibits osteoblasts: reduces rate of calcium deposition in bone

152 4 Effects of PTH It enhances reabsorption of Ca2+ at kidneys, reducing urinary loss It stimulates formation and secretion of calcitriol at kidneys

153 Calcitriol Effects complement or enhance PTH
Enhances Ca2+, PO43— 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: zona glomerulosa
zona fasciculate 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: Contains exocrine and endocrine cells
inferior border of stomach and proximal portion of small intestine Contains exocrine and endocrine cells

179 Pancreas Figure 18–15

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 Pancreatic Islets Table 18–6

186 Blood Glucose Levels When levels rise: When levels decline:
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 Accelerates glucose uptake
Accelerates glucose utilization and enhanced ATP production Stimulates glycogen formation Stimulates amino acid absorption and protein synthesis Stimulates triglyceride formation in adipose tissue

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

190 3 Effects of Glucagons Stimulates breakdown of glycogen in skeletal muscle and liver cells Stimulates breakdown of triglycerides in adipose tissue 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 Ca2+ 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 Stimulates adrenal production of aldosterone
Stimulates pituitary release of ADH Promotes thirst 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: After ovulation, follicle cells:
principle estrogen is estradiol After ovulation, follicle cells: reorganize into corpus luteum release estrogens and progestins, especially progesterone

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

211 How do hormones interact to produce coordinated physiological responses?

212 Hormone Interactions Antagonistic (opposing) effects
Synergistic (additive) effects Permissive effects: 1 hormone is necessary for another to produce effect 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
GH Thyroid hormones Insulin PTH Calcitriol Reproductive hormones

215 Growth Hormone (GH) In children: In adults:
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 T4 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: alarm phase resistance phase 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
Increased mental alertness Increased energy consumption Mobilization of energy reserves (glycogen and lipids)

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

226 7 Characteristics of Alarm Phase
Drastic reduction in digestion and urine production Increased sweat gland secretion 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
Mobilize remaining lipid and protein reserves Conserve glucose for neural tissues Elevate and stabilize blood glucose concentrations 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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