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. 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 GrowthGH
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