The Endocrine System/ The Autonomic Nervous System

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The Endocrine System/ The Autonomic Nervous System

  1. 1. Chapter 18: The Endocrine System
  2. 2. The Endocrine System Defined: the glands and parts of glands that secrete hormones that integrate and control the body's metabolic activity. Endocrine glands include the pituitary, thyroid, parathyroids, adrenals, pancreas, ovaries, and testes.
  3. 3. Endocrine System • Regulates long-term processes: – growth – development – reproduction • Uses chemical messengers to relay information and instructions between cells
  4. 4. What are the modes of intercellular communication used by the endocrine and nervous systems?
  5. 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. 6. Paracrine Communication • Paracrine • Uses chemical signals to transfer information from cell to cell within single tissue • Most common form of intercellular communication
  7. 7. Endocrine Communication • Endocrine cells release chemicals (hormones) into bloodstream • Alters metabolic activities of many tissues and organs simultaneously
  8. 8. Target Cells • Are specific cells that possess receptors needed to bind and “read” hormonal messages
  9. 9. Hormones • Stimulate synthesis of enzymes or structural proteins • Increase or decrease rate of synthesis • Turn existing enzyme or membrane channel “on” or “off”
  10. 10. Endocrine System • Is unable to handle crisis management • Nervous System • split-second responses
  11. 11. How do the cellular components of the endocrine system compare with those of other tissues and systems?
  12. 12. Endocrine System • Includes all endocrine cells and body tissues that produce hormones or paracrine factors
  13. 13. Endocrine Cells • Glandular secretory cells that release their secretions into extracellular fluid (blood and lymph)
  14. 14. Exocrine Cells • Secrete their products onto epithelial surfaces • Use ducts instead of circulation
  15. 15. What are the major structural classes of hormones?
  16. 16. Hormones • Can be divided into 3 groups: – amino acid derivatives – peptide hormones – lipid derivatives
  17. 17. Amino Acid Derivatives • Small molecules structurally related to amino acids • Synthesized from the amino acids tyrosine and tryptophan
  18. 18. Tyrosine Derivatives • Thyroid hormones • Compounds: – epinephrine (E) – norepinephrine (NE) – dopamine, also called catecholamines
  19. 19. Tryptophan Derivative • Melatonin: – produced by pineal gland
  20. 20. Peptide Hormones • Chains of amino acids • Synthesized as prohormones: – inactive molecules converted to active hormones before or after secretion
  21. 21. 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)
  22. 22. 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
  23. 23. 2 Classes of Lipid Derivatives • Eicosanoids: – derived from arachidonic acid • Steroid hormones: – derived from cholesterol
  24. 24. Eicosanoids • Are small molecules with five-carbon ring at one end • Are important paracrine factors • Coordinate cellular activities • Affect enzymatic processes in extracellular fluids
  25. 25. Leukotrienes • Are eicosanoids released by activated white blood cells, or leukocytes • Important in coordinating tissue responses to injury or disease
  26. 26. Prostaglandins • A second group of eicosanoids produced in most tissues of body • Are involved in coordinating local cellular activities
  27. 27. 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)
  28. 28. 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
  29. 29. Classes of Hormones Figure 18–2
  30. 30. Hormones • Circulate freely or bound to transport proteins
  31. 31. 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
  32. 32. Thyroid and Steroid Hormones • Remain in circulation much longer • Enter bloodstream: – more than 99% become attached to special transport proteins
  33. 33. Bloodstream • Contains substantial reserve of bound hormones
  34. 34. What are the general mechanisms of hormonal action?
  35. 35. Hormone Receptor • Is a protein molecule to which a particular molecule binds strongly • Responds to several different hormones
  36. 36. Cells • Different tissues have different combinations of receptors • Presence or absence of specific receptor determines hormonal sensitivity
  37. 37. 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)
  38. 38. Eicosanoids • Are lipid soluble • Diffuse across membrane to reach receptor proteins on inner surface of membrane (intracellular receptors)
  39. 39. Hormone • Binds to receptors in cell membrane • Cannot have direct effect on activities inside target cell • Uses intracellular intermediary to exert effects
  40. 40. Intracellular Intermediaries • First messenger: – leads to second messenger – may act as enzyme activator, inhibitor, or cofactor – results in change in rates of metabolic reactions
  41. 41. Important Second Messengers • Cyclic-AMP (cAMP): – derivative of ATP • Cyclic-GMP (cGMP): – derivative of GTP • Calcium ions
  42. 42. G Protein • Enzyme complex coupled to membrane receptor • Involved in link between first messenger and second messenger • Activated when hormone binds to receptor at membrane surface
  43. 43. G Proteins and Hormone Activity Figure 18–3
  44. 44. G Protein • Changes concentration of second messenger cyclic-AMP (cAMP) within cell • Increased cAMP level accelerates metabolic activity within cell
  45. 45. Increased cAMP Levels (1 of 2) 1. Activated G protein: – activates enzyme adenylate cyclase 2. Adenylate cyclase: – converts ATP to cyclic-AMP
  46. 46. 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
  47. 47. G Proteins and Hormone Activity Figure 18–3
  48. 48. Lower cAMP Levels 1. 2. 3. 4. Activated G protein stimulates PDE activity Inhibits adenylate cyclase activity Levels of cAMP decline cAMP breakdown accelerates; cAMP synthesis is prevented
  49. 49. G Proteins and Hormone Activity Figure 18–3
  50. 50. 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
  51. 51. 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 (IP3) from membrane phospholipids
  52. 52. Steroid Hormones • Cross cell membrane • Bind to receptors in cytoplasm or nucleus, activating or inactivating specific genes
  53. 53. Steroid Hormones Figure 18–4a
  54. 54. Steroid Hormones • Alter rate of DNA transcription in nucleus: – change patterns of protein synthesis • Directly affect metabolic activity and structure of target cell
  55. 55. Thyroid Hormones Figure 18–4b
  56. 56. Thyroid Hormones • Cross cell membrane: – primarily by transport mechanism • Bind to receptors in nucleus and on mitochondria: – activating specific genes – changing rate of transcription
  57. 57. How are endocrine organs controlled?
  58. 58. Endocrine Reflexes • Functional counterparts of neural reflexes • In most cases, controlled by negative feedback mechanisms
  59. 59. Simple Endocrine Reflex • Involves only 1 hormone • Controls hormone secretion by: – Heart (ANF) – Pancreas (insulin, glucagon) – parathyroid gland (calcitonin) – digestive tract
  60. 60. Complex Endocrine Reflex • Involves: – 1 or more intermediary steps – 2 or more hormones • Stimulating, releasing, inhibitory hormones
  61. 61. Endocrine System Figure 18–1
  62. 62. Hypothalamus Figure 18–5
  63. 63. 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
  64. 64. Hypothalamus (2 of 2) 2. Acts as an endocrine organ 3. Contains autonomic centers: – exert direct neural control over endocrine cells of adrenal medullae • Neuroendocrine response
  65. 65. Neuroendocrine Reflexes • Pathways include both neural and endocrine components
  66. 66. Complex Commands • Issued by changing: – amount of hormone secreted – pattern of hormone release • (continuous, pulsed)
  67. 67. Pulses • Hypothalamic and pituitary hormones released in sudden bursts • Frequency varies response of target cells
  68. 68. Where is the pituitary gland located, and what is its relationship to the hypothalamus?
  69. 69. Pituitary Gland Figure 18–6
  70. 70. Pituitary Gland • Also called hypophysis • Lies within sella turcica • Hangs inferior to hypothalamus: – connected by infundibulum
  71. 71. Diaphragma Sellae • Locks pituitary in position • Isolates it from cranial cavity
  72. 72. Pituitary Gland • Releases 9 important peptide hormones • Hormones bind to membrane receptors: – use cAMP as second messenger
  73. 73. Anterior Lobe • Also called adenohypophysis:
  74. 74. Median Eminence • Swelling near attachment of infundibulum • Where hypothalamic neurons release regulatory factors: – into interstitial fluids – through fenestrated capillaries
  75. 75. Median Eminence Figure 18–7
  76. 76. Portal Vessels • Blood vessels link 2 capillary networks • Entire complex is portal system
  77. 77. Hypophyseal Portal System • Ensures that regulatory factors reach intended target cells before entering general circulation
  78. 78. What are the hormones produced by the anterior lobe, and what are the functions of those hormones?
  79. 79. 2 Classes of Hypothalamic Regulatory Hormones 1. Releasing hormones 2. Inhibiting hormones
  80. 80. Hypothalamic Regulatory Hormones • Rate of secretion is controlled by negative feedback Figure 18–8a
  81. 81. Hypothalamic Regulatory Hormones Figure 18–8b
  82. 82. Releasing Hormones (RH) • Stimulate synthesis and secretion of 1 or more hormones at anterior lobe
  83. 83. Inhibiting Hormones (IH) • Prevent synthesis and secretion of hormones from anterior lobe
  84. 84. Anterior Lobe • Hormones “turn on” endocrine glands or support other organs Figure 18–8a
  85. 85. Thyroid-Stimulating Hormone (TSH) • Also called thyrotropin • Triggers release of thyroid hormones
  86. 86. Adrenocorticotropic Hormone (ACTH) • Also called corticotropin • Stimulates release of steroid hormones by adrenal cortex • Targets cells that produce glucocorticoids
  87. 87. Gonadotropins • Regulate activities of gonads (testes, ovaries) • Follicle-stimulating hormone • Luteinizing hormone
  88. 88. Follicle-Stimulating Hormone (FSH) (1 of 2) • Also called follitropin • Stimulates follicle development and estrogen secretion in females
  89. 89. 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
  90. 90. Luteinizing Hormone (LH) • Also called lutropin • Causes ovulation and progestin production in females • Causes androgen production in males
  91. 91. FSH and LH Production • Stimulated by gonadotropin-releasing hormone (GnRH) from hypothalamus: – GnRH production inhibited by estrogens, progestins, and androgens
  92. 92. Prolactin (PRL) • Also called mammotropin • Stimulates development of mammary glands and milk production • Production inhibited by prolactin-inhibiting hormone (PIH)
  93. 93. Prolactin (PRL) • Stimulates PIH release • Inhibits secretion of prolactin-releasing factors (PRF)
  94. 94. Prolactin (PRL) Figure 18–8b
  95. 95. 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)
  96. 96. Melanocyte-Stimulating Hormone (MSH) • Also called melanotropin • Stimulates melanocytes to produce melanin • Inhibited by dopamine
  97. 97. Melanocyte-Stimulating Hormone (MSH) • Secreted during: – fetal development – early childhood – pregnancy – certain diseases
  98. 98. What hormones are produced by the posterior lobe, and what are their functions?
  99. 99. Posterior Lobe • Also called neurohypophysis • Contains unmyelinated axons of hypothalamic neurons • Supraoptic and paraventricular nuclei manufacture: – antidiuretic hormone (ADH) – oxytocin (OT)
  100. 100. Antidiuretic Hormone • Decreases amount of water lost at kidneys • Elevates blood pressure • Release inhibited by alcohol
  101. 101. Oxytocin • Stimulates contractile cells in mammary glands • Stimulates smooth muscles in uterus • Secretion and milk ejection are part of neuroendocrine reflex
  102. 102. Where is the thyroid gland located, and what is its structure?
  103. 103. Thyroid Gland • Lies anterior to thyroid cartilage of larynx • Consists of 2 lobes connected by narrow isthmus
  104. 104. Thyroid Gland Figure 18–10a, b
  105. 105. Thyroid Follicles • Hollow spheres lined by cuboidal epithelium • Cells surround follicle cavity that contains viscous colloid
  106. 106. Thyroid Follicles • Surrounded by network of capillaries that: – deliver nutrients and regulatory hormones – accept secretory products and metabolic wastes
  107. 107. Thyroid Follicles Figure 18–11a, b
  108. 108. Thyroglobulin • • • • Globular protein Synthesized by follicle cells Secreted into colloid of thyroid follicles Molecules contain amino acid tyrosine
  109. 109. Thyroglobulin Figure 18–10c
  110. 110. What hormones are produced by the thyroid gland?
  111. 111. Thyroxine (T4) • Also called tetraiodothyronine • Contains 4 iodide ions
  112. 112. Triiodothyronine (T3) • Contains 3 iodide ions
  113. 113. Rate of Thyroid Hormone Release • Major factor: – TSH concentration in circulating blood Figure 18–11b
  114. 114. Thyroid-Binding Globulins (TBGs) • Transport proteins • Attach to most T4 and T3 molecules
  115. 115. Transthyretin • Also called thyroid-binding prealbumin (TBPA) • Is a transport protein • Attaches to most remaining T4 and T3 molecules
  116. 116. Unbound Thyroid Hormones • Diffuse out of bloodstream and into other tissues • Disturb equilibrium • Carrier proteins release more thyroid hormones until new equilibrium is reached
  117. 117. 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
  118. 118. What are the functions of thyroid hormones, and what are the results of abnormal levels of thyroid hormones?
  119. 119. Thyroid Hormones • Enter target cells by transport system • Affect most cells in body • Bind to receptors in: – cytoplasm – surfaces of mitochondria – nucleus
  120. 120. Calorigenic Effect • Cell consumes more energy resulting in increased heat generation
  121. 121. Thyroid Hormones • In children, essential to normal development of: – skeletal, muscular, and nervous systems
  122. 122. Thyroid Gland • Is responsible for strong, immediate, and short-lived increase in rate of cellular metabolism
  123. 123. Thyroid Gland Table 18–3
  124. 124. 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
  125. 125. C (Clear) Cells • Produce calcitonin (CT): – helps regulate concentrations of Ca2+ in body fluids
  126. 126. Where are the parathyroid glands?
  127. 127. Parathyroid Glands • Embedded in posterior surface of thyroid gland Figure 18–12
  128. 128. What is the function of the hormone produced by the parathyroid glands?
  129. 129. Parathyroid Hormone (PTH) • Produced by chief cells • In response to low concentrations of Ca2+
  130. 130. 4 Effects of PTH 1. It stimulates osteoclasts: – accelerates mineral turnover – releases Ca2+ from bone 2. It inhibits osteoblasts: – reduces rate of calcium deposition in bone 3. It enhances reabsorption of Ca2+ at kidneys, reducing urinary loss 4. It stimulates formation and secretion of calcitriol at kidneys
  131. 131. Calcitriol • Effects complement or enhance PTH • Enhances Ca2+, PO43— absorption by digestive tract
  132. 132. Parathyroid Glands • Primary regulators of blood calcium I levels in adults Figure 18–13
  133. 133. What are the location, structure, and general functions of the adrenal gland?
  134. 134. Adrenal Glands • Lie along superior border of each kidney • Subdivided into superficial adrenal cortex and an inner adrenal medulla
  135. 135. Adrenal Cortex • Subdivided into 3 regions: 1. zona glomerulosa 2. zona fasciculate 3. zona reticularis
  136. 136. What hormones are produced by the adrenal glands, and what are their functions?
  137. 137. Zona Glomerulosa • Outer region of adrenal cortex • Produces mineralocorticoids: – e.g., aldosterone
  138. 138. Aldosterone • Stimulates: – conservation of sodium ions – elimination of potassium ions • Increases sensitivity of salt receptors in taste buds
  139. 139. Aldosterone • Secretion responds to: – – – – Rise in blood Na+ drop in blood K+ concentration blood volume blood pressure
  140. 140. Zona Fasciculata • Produces glucocorticoids • Endocrine cells are larger and contain more lipids than zona glomerulosa
  141. 141. Zona Fasciculata • Secretes cortisol (hydrocortisone) with corticosterone: – liver converts cortisol to cortisone
  142. 142. Glucocorticoids • Secretion regulated by negative feedback • Have inhibitory effect on production of: – corticotropin-releasing hormone (CRH) in hypothalamus – ACTH in anterior lobe
  143. 143. Glucocorticoids • Accelerate glucose synthesis and glycogen formation • Show anti-inflammatory effects: – inhibit activities of white blood cells and other components of immune system
  144. 144. Zona Reticularis • Network of endocrine cells • Forms narrow band bordering each adrenal medulla • Produces androgens under stimulation by ACTH
  145. 145. Adrenal Medullae • Secretory activities controlled by sympathetic division of ANS • Produces epinephrine (adrenaline) and norepinephrine • Metabolic changes persist for several minutes
  146. 146. Where is the pineal gland, and what are the functions of the hormone it produces?
  147. 147. Pineal Gland • Lies in posterior portion of roof of third ventricle • Contains pinealocytes: – synthesize hormone melatonin
  148. 148. Functions of Melatonin • Inhibiting reproductive functions • Protecting against damage by free radicals • *Setting circadian rhythms – (your 24 hr cycle)
  149. 149. Where is the pancreas, and what is its structure?
  150. 150. Pancreas • Lies between: – inferior border of stomach – and proximal portion of small intestine • Contains exocrine and endocrine cells
  151. 151. Pancreas Figure 18–15
  152. 152. Endocrine Pancreas • Cells form clusters: – pancreatic islets, or islets of Langerhans
  153. 153. What hormones are produced by the pancreas, and what are their functions?
  154. 154. 4 Types of Cells in Pancreatic Islets • Alpha cells: – produce glucagon • Beta cells: – secrete insulin
  155. 155. 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
  156. 156. Insulin • Is a peptide hormone released by beta cells • Affects target cells
  157. 157. 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
  158. 158. Glucagons • Released by alpha cells • Mobilize energy reserves • Affects target cells
  159. 159. 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
  160. 160. What are the functions of hormones produced by the kidneys, heart, thymus, testes, ovaries, and adipose tissue?
  161. 161. Intestines • Produce hormones important to coordination of digestive activities
  162. 162. Kidneys • Produce the hormones calcitriol and erythropoietin • Produce the enzyme (hormone?) renin
  163. 163. Calcitriol • Stimulates calcium and phosphate ion absorption along digestive tract Figure 18–17a
  164. 164. Effects of Calcitriol on Calcium Metabolism • Stimulates formation and differentiation of osteoprogenitor cells and osteoclasts • Stimulates bone resorption by osteoclasts
  165. 165. Effects of Calcitriol on Calcium Metabolism • Stimulates Ca2+ reabsorption at kidneys • Suppresses parathyroid hormone (PTH) production
  166. 166. Erythropoietin (EPO) • Stimulates red blood cell production by bone marrow: – increased RBCs elevate blood volume
  167. 167. Renin • Converts angiotensinogen to angiotensin I in liver • Angiotensin I is converted to angiotensin II (in lungs via ACE)
  168. 168. Angiotensin II 1. Stimulates adrenal production of aldosterone 2. Stimulates pituitary release of ADH 3. Promotes thirst 4. Elevates blood pressure
  169. 169. The Renin–Angiotensin System Figure 18–17b
  170. 170. Heart • Produces atrial natriuretic peptides (ANP and BNP): – when blood volume becomes excessive
  171. 171. Natriuretic Peptide • Action opposes angiotensin II • Resulting in reduction in blood volume and blood pressure
  172. 172. Thymus • Produces thymosin hormones: – that helps develop and maintain normal immune defenses – Promotes T cell maturation
  173. 173. Testes • Produce androgens in interstitial cells: – testosterone: • is most important male hormone • Secrete inhibin in sustentacular cells: – support differentiation and physical maturation of sperm
  174. 174. Ovaries • Produce estrogens: – principle estrogen is estradiol • After ovulation, follicle cells: – reorganize into corpus luteum – release estrogens and progestins, especially progesterone
  175. 175. Adipose Tissue Secretions 1. Leptin: – feedback control for appetite – controls normal levels of GnRH, gonadotropin synthesis 2. Resistin: – reduces insulin sensitivity
  176. 176. Chapter 16 Autonomic Nervous System
  177. 177. Autonomic Nervous System (ANS) • Operates without conscious instruction • Part of peripheral nervous system • Coordinates systems functions: – cardiovascular – respiratory – digestive – urinary – reproductive
  178. 178. Visceral Motor Neurons • In brain stem and spinal cord, are known as preganglionic neurons • (Ganglia- clusters of neuronal cell bodies and their dendrites)
  179. 179. Preganglionic Fibers • Axons of preganglionic neurons • Leave CNS and synapse on ganglionic neurons
  180. 180. Autonomic Ganglia • Peripheral ganglia • Contain many ganglionic neurons • Ganglionic neurons innervate visceral (pertaining to the internal organs) effectors: – cardiac muscle – smooth muscle – glands – adipose tissues
  181. 181. Postganglionic Fibers • Axons of ganglionic neurons • Begin at autonomic ganglia: – extend to peripheral target organs
  182. 182. What are the divisions and functions of the ANS?
  183. 183. Sympathetic Division • “Kicks in” only during exertion, stress, or emergency Parasympathetic Division • Controls during resting conditions
  184. 184. Divisions of the ANS • 2 divisions may work together or independently:
  185. 185. Sympathetic Division • Preganglionic fibers (thoracic and superior lumbar) synapse in ganglia near spinal cord • Preganglionic fibers are short • Postganglionic fibers are long
  186. 186. Sympathetic Chain • • • • • 3 cervical ganglia 10–12 thoracic ganglia 4–5 lumbar ganglia 4–5 sacral ganglia 1 coccygeal ganglion
  187. 187. 7 Responses to Increased Sympathetic Activity (Fight or Flight) 1. Heightened mental alertness 2. Increased metabolic rate 3.Reduced digestive and urinary functions 4.Energy reserves activated 1. 5. Increased respiratory rate and respiratory passageways dilate 5. 6. Increased heart rate and blood pressure 6. 7. Sweat glands activated
  188. 188. Parasympathetic Division • Preganglionic fibers originate in brain stem and sacral segments of spinal cord • Synapse in ganglia close to (or within) target organs • Preganglionic fibers are long • Postganglionic fibers are short
  189. 189. Parasympathetic-Rest and Repose or Breed, Feed, & Read • Parasympathetic division stimulates visceral activity • Conserves energy and promotes sedentary activities
  190. 190. Pattern of Responses to Increased Levels of Parasympathetic Activity • Decreased: – metabolic rate – heart rate and blood pressure • Increased: – salivary and digestive glands secretion – motility and blood flow in digestive tract – Urination and defecation stimulation
  191. 191. ANS: Sympathetic Division Figure 16–3
  192. 192. Structure of the Sympathetic Division • Preganglionic neurons located between segments T1 and L2 of spinal cord • Ganglionic neurons in ganglia near vertebral column
  193. 193. Ganglionic Neurons • Occur in 3 locations: – sympathetic chain ganglia – collateral ganglia – adrenal medullae Figure 16–4
  194. 194. Collateral ganglia
  195. 195. The Adrenal Medullae Figure 16–4c
  196. 196. The Adrenal Medullae Modified Sympathetic Ganglion • At the center of each adrenal gland in area known as adrenal medulla • Very short axons • When stimulated, release neurotransmitters into bloodstream (not at synapse) • Functions as hormones affect target cells throughout body
  197. 197. What are the mechanisms of neurotransmitter release in the sympathetic division?
  198. 198. Neuroendocrine Cells of Adrenal Medullae • Secrete hormones epinephrine (E) and norepinephrine (NE)
  199. 199. Epinephrine • Also called adrenaline • Is 75–80% of secretory output • Remaining is noradrenaline (NE)
  200. 200. Distribution • Bloodstream carries hormones through body • Causing changes in metabolic activities of different cells
  201. 201. Differences from Sympathetic Postganglionic Fiber Stimulation • Cells not innervated by sympathetic postganglionic fibers • Effects last longer: – hormones continue to diffuse out of bloodstream
  202. 202. Sympathetic Division • Can change activities of tissues and organs by: – releasing NE at peripheral synapses – distributing E and NE throughout body in bloodstream
  203. 203. Crisis Mode • Entire division responds (sympathetic activation) • Are controlled by sympathetic centers in hypothalamus • Effects are not limited to peripheral tissues • Alters CNS activity as well
  204. 204. Cholinergic Synapses • Use ACh as transmitter • Excitatory effect on ganglionic neurons
  205. 205. Adrenergic Neurons • Use NE as neurotransmitter
  206. 206. NE Released by Varicosities • Affects targets until reabsorbed or inactivated • 50–80% of NE is reabsorbed by varicosities: – is reused or broken down by MAO • The rest diffuses out or is broken down by COMT
  207. 207. Duration of Effects on Postsynaptic Membrane • NE persist for a few seconds • ACh only for 20 msec
  208. 208. Effects of Sympathetic Stimulation • Primarily from interactions of NE and E with adrenergic membrane receptors
  209. 209. 2 Classes of Sympathetic Receptors • Alpha receptors • Beta receptors
  210. 210. Norepinephrine • Stimulates alpha receptors to greater degree than beta receptors
  211. 211. Epinephrine • Stimulates both classes of receptors
  212. 212. Localized Sympathetic Activity • Involves release of NE at varicosities • Primarily affects alpha receptors near active varicosities
  213. 213. Generalized Sympathetic Activation • Release of Epinephrine by adrenal medulla • Affect alpha and beta receptors throughout body
  214. 214. Alpha and Beta Receptors • G proteins
  215. 215. What are the effects of sympathetic neurotransmitters on target organs and tissues?
  216. 216. Stimulation of Alpha (a) Receptors • Activates enzymes on inside of cell membrane
  217. 217. Alpha Receptors • Alpha-1 (a1) • Alpha-2 (a2)
  218. 218. Beta Receptors • Two types: – Beta-1 (b1) – Beta-2 (b2)
  219. 219. Beta-1 (b1) • Increases metabolic activity
  220. 220. Beta-2 (b2) • Causes inhibition • Triggers relaxation of smooth muscles along respiratory tract
  221. 221. Beta-3 (b3) • Is found in adipose tissue • Leads to lipolysis, the breakdown of triglycerides in adipocytes • Releases fatty acids into circulation
  222. 222. Sympathetic Postganglionic Fibers • Mostly adrenergic (release NE) • A few cholinergic (release ACh) • Innervate sweat glands of skin and blood vessels of skeletal muscles and brain • Stimulate sweat gland secretion and dilates blood vessels
  223. 223. ACh • Released by parasympathetic division • Body wall and skeletal muscles are not innervated by parasympathetic division • Both NE and ACh needed to regulate visceral functions
  224. 224. What are the structures and functions of the parasympathetic division of the autonomic nervous system?
  225. 225. ANS: The Parasympathetic Division Figure 16–7
  226. 226. Autonomic Nuclei • Are contained in the mesencephalon, pons, and medulla oblongata: – associated with cranial nerves III, VII, IX, X • In lateral gray horns of spinal segments S2–S4
  227. 227. Ganglionic Neurons in Peripheral Ganglia • Preganglionic fiber synapses on 6–8 ganglionic neurons: – terminal ganglion: • near target organ • usually paired – intramural ganglion: • embedded in tissues of target organ • interconnected masses • clusters of ganglion cells
  228. 228. Pattern of Parasympathetic Division • All ganglionic neurons in same ganglion • Postganglionic fibers influence same target organ • Effects of parasympathetic stimulation more specific and localized
  229. 229. What are the mechanisms of neurotransmitter release in the parasympathetic division?
  230. 230. Parasympathetic Preganglionic Fibers • Leave brain as components of cranial nerves: – III (oculomotor) – VII (facial) – IX (glossopharyngeal) – X (vagus)
  231. 231. Parasympathetic Innervation Figure 16–8
  232. 232. Vagus Nerve • Preganglionic parasympathetic innervation to structures in: – neck – thoracic and abdominopelvic cavity – distal portion of large intestine
  233. 233. Vagus Nerve • Provides 75% of all parasympathetic outflow • Branches intermingle with fibers of sympathetic division
  234. 234. Sacral Segments of Spinal Cord • Preganglionic fibers carry sacral parasympathetic output • Do not join ventral roots of spinal nerves
  235. 235. Pelvic Nerves • Innervate intramural ganglia in walls of: – kidneys – urinary bladder – portions of large intestine – sex organs
  236. 236. What are the effects of parasympathetic neurotransmitters on target organs and tissues?
  237. 237. Parasympathetic Activation • Centers on relaxation, food processing, and energy absorption • Localized effects, last a few seconds at most
  238. 238. 10 Effects of Parasympathetic Activation 1. Constriction of pupils: – restricts light entering eyes 2. Secretion by digestive glands: – exocrine and endocrine
  239. 239. 10 Effects of Parasympathetic Activation 3. Secretion of hormones 4. Changes in blood flow and glandular activity: – associated with sexual arousal
  240. 240. 10 Effects of Parasympathetic Activation 5. Increases smooth muscle activity: – along digestive tract 6. Defecation: – stimulation and coordination
  241. 241. 10 Effects of Parasympathetic Activation 7. Contraction of urinary bladder: – during urination 8. Constriction of respiratory passageways
  242. 242. 10 Effects of Parasympathetic Activation 9. Reduction in heart rate: – and force of contraction 10. Sexual arousal: – stimulation of sexual glands
  243. 243. Anabolic System • Stimulation increases nutrient content of blood • Cells absorb nutrients
  244. 244. Parasympathetic Neurons • All release ACh as neurotransmitter • Effects vary widely
  245. 245. ACh • Inactivated by by enzyme acetylcholinersterase (AChE) at synapse • Ach is also inactivated by pseudocholinesterase in surrounding tissues
  246. 246. 2 Types of ACh Receptors on Postsynaptic Membranes • Nicotinic receptors • Muscarinic receptors
  247. 247. Nicotinic Receptors • On surfaces of ganglion cells (sympathetic and parasympathetic) • At neuromuscular junctions of somatic nervous system
  248. 248. Action of Nicotinic Receptors • Exposure to ACh causes excitation of ganglionic neuron or muscle fiber • Open chemically gated channels in postsynaptic membrane
  249. 249. Dangerous Environmental Toxins • Muscarine: – binds to muscarinic receptors – targets parasympathetic neuromuscular or neuroglandular junctions
  250. 250. Summary: Parasympathetic Division • Ganglionic neurons located in or next to target organs
  251. 251. Summary: Parasympathetic Division • Innervates areas served by: – cranial nerves – organs in thoracic – organs in abdominopelvic cavities
  252. 252. Summary: Parasympathetic Division • All neurons are cholinergic: – ganglionic neurons have nicotinic receptors, excited by ACh – muscarinic receptors at neuromuscular or neuroglandular junctions produce either excitation or inhibition
  253. 253. Summary: Parasympathetic Division • Effects of stimulation are brief and restricted to specific organs and sites
  254. 254. Comparing Sympathetic and Parasympathetic Divisions • Sympathetic: – widespread impact – reaches organs and tissues throughout body • Parasympathetic: – innervates only specific visceral structures
  255. 255. Differences between Sympathetic and Parasympathetic Divisions Figure 16–9
  256. 256. What is the relationship between the two divisions of the autonomic nervous system, and the significance of dual innervation?
  257. 257. Dual Innervation • Most vital organs receive instructions from both sympathetic and parasympathetic divisions • 2 divisions commonly have opposing effects
  258. 258. Anatomy of Dual Innervation • Parasympathetic postganglionic fibers accompany cranial nerves to peripheral destinations • Sympathetic innervation reaches same structures by traveling directly from superior cervical ganglia of sympathetic chain
  259. 259. Structure: Autonomic Plexuses • Nerve networks in the thoracic and abdominopelvic cavities: – are formed by mingled sympathetic postganglionic fibers and parasympathetic preganglionic fibers • Travel with blood and lymphatic vessels that supply visceral organs
  260. 260. 6 Autonomic Plexuses 1. 2. 3. 4. 5. 6. Cardiac plexus Pulmonary plexus Esophageal plexus Celiac plexus Inferior mesenteric plexus Hypogastric plexus
  261. 261. Why is autonomic tone important?
  262. 262. Autonomic Tone • Is an important aspect of ANS function: – if nerve is inactive under normal conditions, can only increase activity – if nerve maintains background level of activity, can increase or decrease activity
  263. 263. Autonomic Tone and Dual Innervation • Significant where dual innervation occurs: – 2 divisions have opposing effects • More important when dual innervation does not occur

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