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© 2013 Pearson Education, Inc. Endocrine System: Overview Acts with nervous system to coordinate and integrate activity of body cells Influences metabolic.

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Presentation on theme: "© 2013 Pearson Education, Inc. Endocrine System: Overview Acts with nervous system to coordinate and integrate activity of body cells Influences metabolic."— Presentation transcript:

1 © 2013 Pearson Education, Inc. Endocrine System: Overview Acts with nervous system to coordinate and integrate activity of body cells Influences metabolic activities via hormones transported in blood Response slower but longer lasting than nervous system Endocrinology –Study of hormones and endocrine organs

2 © 2013 Pearson Education, Inc. Endocrine System: Overview Controls and integrates –Reproduction –Growth and development –Maintenance of electrolyte, water, and nutrient balance of blood –Regulation of cellular metabolism and energy balance –Mobilization of body defenses

3 © 2013 Pearson Education, Inc. Endocrine System: Overview Exocrine glands –Nonhormonal substances (sweat, saliva) –Have ducts to carry secretion to membrane surface Endocrine glands –Produce hormones –Lack ducts

4 © 2013 Pearson Education, Inc. Endocrine System: Overview Endocrine glands: pituitary, thyroid, parathyroid, adrenal, and pineal glands Hypothalamus is Neuroendocrine organ Some have exocrine and endocrine functions –Pancreas, gonads, placenta Other tissues and organs that produce hormones –Adipose cells, thymus, and cells in walls of small intestine, stomach, kidneys, and heart

5 © 2013 Pearson Education, Inc. Figure 16.1 Location of selected endocrine organs of the body. Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Adrenal glands Pancreas Gonads Testis (male) Ovary (female)

6 © 2013 Pearson Education, Inc. Chemical Messengers Hormones: long-distance chemical signals; travel in blood or lymph Autocrines: chemicals that exert effects on same cells that secrete them Paracrines: locally acting chemicals that affect cells other than those that secrete them Autocrines and paracrines are local chemical messengers; not considered part of endocrine system

7 © 2013 Pearson Education, Inc. Chemistry of Hormones Two main classes –Amino acid-based hormones Amino acid derivatives, peptides, and proteins –Steroids Synthesized from cholesterol Gonadal and adrenocortical hormones

8 © 2013 Pearson Education, Inc. Mechanisms of Hormone Action Though hormones circulate systemically only cells with receptors for that hormone affected Target cells –Tissues with receptors for specific hormone Hormones alter target cell activity

9 © 2013 Pearson Education, Inc. Mechanisms of Hormone Action Hormone action on target cells may be to –Alter plasma membrane permeability and/or membrane potential by opening or closing ion channels –Stimulate synthesis of enzymes or other proteins –Activate or deactivate enzymes –Induce secretory activity –Stimulate mitosis

10 © 2013 Pearson Education, Inc. Mechanisms of Hormone Action Hormones act at receptors in one of two ways, depending on their chemical nature and receptor location 1.Water-soluble hormones (all amino acid– based hormones except thyroid hormone) Act on plasma membrane receptors Act via G protein second messengers Cannot enter cell

11 © 2013 Pearson Education, Inc. Mechanisms of Hormone Action 2.Lipid-soluble hormones (steroid and thyroid hormones) Act on intracellular receptors that directly activate genes Can enter cell

12 © 2013 Pearson Education, Inc. Plasma Membrane Receptors and Second- messenger Systems cAMP signaling mechanism: 1.Hormone (first messenger) binds to receptor 2.Receptor activates G protein 3.G protein activates adenylate cyclase 4.Adenylate cyclase converts ATP to cAMP (second messenger) 5.cAMP activates protein kinases that phosphorylate proteins

13 © 2013 Pearson Education, Inc. Plasma Membrane Receptors and Second- messenger Systems cAMP signaling mechanism –Activated kinases phosphorylate various proteins, activating some and inactivating others –cAMP is rapidly degraded by enzyme phosphodiesterase –Intracellular enzymatic cascades have huge amplification effect

14 © 2013 Pearson Education, Inc. Slide 1 Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones. Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) ReceptorG proteinEnzyme2nd messenger Adenylate cyclase Extracellular fluid G protein (G s ) GDP Receptor Hormone (1st messenger) binds receptor. Receptor activates G protein (G s ). G protein activates adenylate cyclase. Adenylate cyclase converts ATP to cAMP (2nd messenger). Inactive protein kinase Triggers responses of target cell (activates enzymes, stimulates cellular secretion, opens ion channel, etc.) Active protein kinase cAMP activates protein kinases. Cytoplasm cAMP GTP ATP

15 © 2013 Pearson Education, Inc. Slide 2 Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones. Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) ReceptorG proteinEnzyme2nd messenger Hormone (1st messenger) binds receptor. 1 Extracellular fluid Receptor Cytoplasm

16 © 2013 Pearson Education, Inc. Slide 3 Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones. Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) ReceptorG proteinEnzyme2nd messenger Extracellular fluid Hormone (1st messenger) binds receptor. 1 G protein (G s ) GDP Receptor GTP Receptor activates G protein (G s ). 2 Cytoplasm

17 © 2013 Pearson Education, Inc. Slide 4 Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones. Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) ReceptorG proteinEnzyme2nd messenger Adenylate cyclase Extracellular fluid G protein (G s ) GDP Receptor Hormone (1st messenger) binds receptor. Receptor activates G protein (G s ). G protein activates adenylate cyclase. Cytoplasm GTP 1 23

18 © 2013 Pearson Education, Inc. Slide 5 Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones. Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) ReceptorG proteinEnzyme2nd messenger Adenylate cyclase Extracellular fluid G protein (G s ) GDP Receptor Hormone (1st messenger) binds receptor. Receptor activates G protein (G s ). G protein activates adenylate cyclase. Adenylate cyclase converts ATP to cAMP (2nd messenger). Cytoplasm cAMP GTP ATP 1 234

19 © 2013 Pearson Education, Inc. Slide 6 Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones. Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) ReceptorG proteinEnzyme2nd messenger Adenylate cyclase Extracellular fluid G protein (G s ) GDP Receptor Hormone (1st messenger) binds receptor. Receptor activates G protein (G s ). G protein activates adenylate cyclase. Adenylate cyclase converts ATP to cAMP (2nd messenger). Inactive protein kinase Triggers responses of target cell (activates enzymes, stimulates cellular secretion, opens ion channel, etc.) Active protein kinase cAMP activates protein kinases. Cytoplasm cAMP GTP ATP

20 © 2013 Pearson Education, Inc. Plasma Membrane Receptors and Second- messenger Systems PIP 2 -calcium signaling mechanism –Involves G protein and membrane-bound effector – phospholipase C –Phospholipase C splits PIP 2 into two second messengers – diacylglycerol (DAG) and inositol trisphosphate (IP 3 ) DAG activates protein kinase; IP 3 causes Ca 2+ release Calcium ions act as second messenger

21 © 2013 Pearson Education, Inc. Plasma Membrane Receptors and Second- messenger Systems –Ca 2+ alters enzyme activity and channels, or binds to regulatory protein calmodulin –Calcium-bound calmodulin activates enzymes that amplify cellular response

22 © 2013 Pearson Education, Inc. Other Signaling Mechanisms Cyclic guanosine monophosphate (cGMP) is second messenger for some hormones Some work without second messengers –E.g., insulin receptor is tyrosine kinase enzyme that autophosphorylates upon insulin binding docking for relay proteins that trigger cell responses

23 © 2013 Pearson Education, Inc. Intracellular Receptors and Direct Gene Activation Steroid hormones and thyroid hormone 1.Diffuse into target cells and bind with intracellular receptors 2.Receptor-hormone complex enters nucleus; binds to specific region of DNA 3.Prompts DNA transcription to produce mRNA 4.mRNA directs protein synthesis 5.Promote metabolic activities, or promote synthesis of structural proteins or proteins for export from cell

24 © 2013 Pearson Education, Inc. Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones. Slide 1 The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 5 The receptor- hormone complex enters the nucleus. The receptor- hormone complex binds a specific DNA region. Binding initiates transcription of the gene to mRNA. The mRNA directs protein synthesis. New protein Nucleus mRNA DNA Receptor Binding region Receptor- hormone complex Receptor protein Steroid hormone Plasma membrane Extracellular fluid Cytoplasm 2 3 4

25 © 2013 Pearson Education, Inc. Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones. Slide 2 The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 Nucleus Receptor protein Steroid hormone Plasma membrane Extracellular fluid Cytoplasm Receptor- hormone complex

26 © 2013 Pearson Education, Inc. Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones. Slide 3 The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 The receptor- hormone complex enters the nucleus. Nucleus Receptor- hormone complex Receptor protein Steroid hormone Plasma membrane Extracellular fluid Cytoplasm 2

27 © 2013 Pearson Education, Inc. Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones. Slide 4 The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 The receptor- hormone complex enters the nucleus. The receptor- hormone complex binds a specific DNA region. Nucleus DNA Receptor Binding region Receptor- hormone complex Receptor protein Steroid hormone Plasma membrane Extracellular fluid Cytoplasm 2 3

28 © 2013 Pearson Education, Inc. Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones. Slide 5 The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 The receptor- hormone complex enters the nucleus. The receptor- hormone complex binds a specific DNA region. Binding initiates transcription of the gene to mRNA. Nucleus mRNA DNA Receptor Binding region Receptor- hormone complex Receptor protein Steroid hormone Plasma membrane Extracellular fluid Cytoplasm 2 3 4

29 © 2013 Pearson Education, Inc. Slide 6 Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones. The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 5 The receptor- hormone complex enters the nucleus. The receptor- hormone complex binds a specific DNA region. Binding initiates transcription of the gene to mRNA. The mRNA directs protein synthesis. New protein Nucleus mRNA DNA Receptor Binding region Receptor- hormone complex Receptor protein Steroid hormone Plasma membrane Extracellular fluid Cytoplasm 2 3 4

30 © 2013 Pearson Education, Inc. Target Cell Specificity Target cells must have specific receptors to which hormone binds, for example –ACTH receptors found only on certain cells of adrenal cortex –Thyroxin receptors are found on nearly all cells of body

31 © 2013 Pearson Education, Inc. Target Cell Activation Target cell activation depends on three factors –Blood levels of hormone –Relative number of receptors on or in target cell –Affinity of binding between receptor and hormone

32 © 2013 Pearson Education, Inc. Target Cell Activation Hormones influence number of their receptors –Up-regulationtarget cells form more receptors in response to low hormone levels –Down-regulationtarget cells lose receptors in response to high hormone levels

33 © 2013 Pearson Education, Inc. Control of Hormone Release Blood levels of hormones –Controlled by negative feedback systems –Vary only within narrow, desirable range Endocrine gland stimulated to synthesize and release hormones in response to –Humoral stimuli –Neural stimuli –Hormonal stimuli

34 © 2013 Pearson Education, Inc. Humoral Stimuli Changing blood levels of ions and nutrients directly stimulate secretion of hormones Example: Ca 2+ in blood –Declining blood Ca 2+ concentration stimulates parathyroid glands to secrete PTH (parathyroid hormone) –PTH causes Ca 2+ concentrations to rise and stimulus is removed

35 © 2013 Pearson Education, Inc. Figure 16.4a Three types of endocrine gland stimuli. Slide 1 Humoral Stimulus Hormone release caused by altered levels of certain critical ions or nutrients. Stimulus: Low concentration of Ca 2+ in capillary blood. Parathyroid glands Parathyroid glands Capillary (low Ca 2+ in blood) Thyroid gland (posterior view) PTH Response: Parathyroid glands secrete parathyroid hormone (PTH), which increases blood Ca 2+.

36 © 2013 Pearson Education, Inc. Figure 16.4a Three types of endocrine gland stimuli. Slide 2 Humoral Stimulus Hormone release caused by altered levels of certain critical ions or nutrients. Parathyroid glands Parathyroid glands Capillary (low Ca 2+ in blood) Thyroid gland (posterior view)

37 © 2013 Pearson Education, Inc. Figure 16.4a Three types of endocrine gland stimuli. Slide 3 Humoral Stimulus Hormone release caused by altered levels of certain critical ions or nutrients. Stimulus: Low concentration of Ca 2+ in capillary blood. Parathyroid glands Parathyroid glands Capillary (low Ca 2+ in blood) Thyroid gland (posterior view) PTH Response: Parathyroid glands secrete parathyroid hormone (PTH), which increases blood Ca 2+.

38 © 2013 Pearson Education, Inc. Neural Stimuli Nerve fibers stimulate hormone release –Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines

39 © 2013 Pearson Education, Inc. Figure 16.4b Three types of endocrine gland stimuli. Slide 1 Neural Stimulus Hormone release caused by neural input. Stimulus: Action potentials in preganglionic sympathetic fibers to adrenal medulla. CNS (spinal cord) Preganglionic sympathetic fibers Medulla of adrenal gland Capillary Response: Adrenal medulla cells secrete epinephrine and norepinephrine.

40 © 2013 Pearson Education, Inc. Figure 16.4b Three types of endocrine gland stimuli. Slide 2 Neural Stimulus Hormone release caused by neural input. CNS (spinal cord) Preganglionic sympathetic fibers Medulla of adrenal gland Capillary

41 © 2013 Pearson Education, Inc. Figure 16.4b Three types of endocrine gland stimuli. Slide 3 Neural Stimulus Hormone release caused by neural input. Stimulus: Action potentials in preganglionic sympathetic fibers to adrenal medulla. CNS (spinal cord) Preganglionic sympathetic fibers Medulla of adrenal gland Capillary Response: Adrenal medulla cells secrete epinephrine and norepinephrine.

42 © 2013 Pearson Education, Inc. Hormonal Stimuli Hormones stimulate other endocrine organs to release their hormones –Hypothalamic hormones stimulate release of most anterior pituitary hormones –Anterior pituitary hormones stimulate targets to secrete still more hormones –Hypothalamic-pituitary-target endocrine organ feedback loop: hormones from final target organs inhibit release of anterior pituitary hormones

43 © 2013 Pearson Education, Inc. Figure 16.4c Three types of endocrine gland stimuli. Slide 1 Hormonal Stimulus Hormone release caused by another hormone (a tropic hormone). Stimulus: Hormones from hypothalamus. Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (Testis) Hypothalamus Response: Anterior pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones.

44 © 2013 Pearson Education, Inc. Figure 16.4c Three types of endocrine gland stimuli. Slide 2 Hormonal Stimulus Hormone release caused by another hormone (a tropic hormone). Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (Testis) Hypothalamus

45 © 2013 Pearson Education, Inc. Figure 16.4c Three types of endocrine gland stimuli. Slide 3 Hormonal Stimulus Hormone release caused by another hormone (a tropic hormone). Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (Testis) Hypothalamus

46 © 2013 Pearson Education, Inc. Figure 16.4c Three types of endocrine gland stimuli. Slide 4 Hormonal Stimulus Hormone release caused by another hormone (a tropic hormone). Stimulus: Hormones from hypothalamus. Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (Testis) Hypothalamus Response: Anterior pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones.

47 © 2013 Pearson Education, Inc. Nervous System Modulation Nervous system modifies stimulation of endocrine glands and their negative feedback mechanisms –Example: under severe stress, hypothalamus and sympathetic nervous system activated body glucose levels rise Nervous system can override normal endocrine controls

48 © 2013 Pearson Education, Inc. Hormones in the Blood Hormones circulate in blood either free or bound –Steroids and thyroid hormone are attached to plasma proteins –All others circulate without carriers Concentration of circulating hormone reflects –Rate of release –Speed of inactivation and removal from body

49 © 2013 Pearson Education, Inc. Hormones in the Blood Hormones removed from blood by –Degrading enzymes –Kidneys –Liver Half-lifetime required for hormone's blood level to decrease by half –Varies from fraction of minute to a week

50 © 2013 Pearson Education, Inc. Onset of Hormone Activity Some responses ~ immediate Some, especially steroid, hours to days Some must be activated in target cells

51 © 2013 Pearson Education, Inc. Duration of Hormone Activity Limited –Ranges from 10 seconds to several hours –Effects may disappear as blood levels drop –Some persist at low blood levels

52 © 2013 Pearson Education, Inc. Interaction of Hormones at Target Cells Multiple hormones may act on same target at same time –Permissiveness: one hormone cannot exert its effects without another hormone being present –Synergism: more than one hormone produces same effects on target cell amplification –Antagonism: one or more hormones oppose(s) action of another hormone

53 © 2013 Pearson Education, Inc. The Pituitary Gland and Hypothalamus Pituitary gland (hypophysis) has two major lobes –Posterior pituitary (lobe) Neural tissue –Anterior pituitary (lobe) (adenohypophysis) Glandular tissue

54 © 2013 Pearson Education, Inc. Pituitary-hypothalamic Relationships Posterior pituitary (lobe) –Downgrowth of hypothalamic neural tissue –Neural connection to hypothalamus (hypothalamic-hypophyseal tract) –Nuclei of hypothalamus synthesize neurohormones oxytocin and antidiuretic hormone (ADH) –Neurohormones are transported to and stored in posterior pituitary

55 © 2013 Pearson Education, Inc. Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). Slide 1 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). Oxytocin and ADH are stored in axon terminals in the posterior pituitary. When hypothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood Oxytocin ADH Posterior lobe of pituitary Optic chiasma Infundibulum (connecting stalk) Hypothalamic- hypophyseal tract Axon terminals Posterior lobe of pituitary Paraventricular nucleus Hypothalamus Supraoptic nucleus Inferior hypophyseal artery Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary.

56 © 2013 Pearson Education, Inc. Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). Slide 2 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). 1 Posterior lobe of pituitary Optic chiasma Infundibulum (connecting stalk) Axon terminals Paraventricular nucleus Hypothalamus Supraoptic nucleus Inferior hypophyseal artery Hypothalamic- hypophyseal tract Posterior lobe of pituitary

57 © 2013 Pearson Education, Inc. Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). Slide 3 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). 1 2 Posterior lobe of pituitary Optic chiasma Infundibulum (connecting stalk) Axon terminals Paraventricular nucleus Hypothalamus Supraoptic nucleus Inferior hypophyseal artery Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary. Hypothalamic- hypophyseal tract Posterior lobe of pituitary

58 © 2013 Pearson Education, Inc. Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). Slide 4 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). Oxytocin and ADH are stored in axon terminals in the posterior pituitary Posterior lobe of pituitary Optic chiasma Infundibulum (connecting stalk) Axon terminals Paraventricular nucleus Hypothalamus Supraoptic nucleus Inferior hypophyseal artery Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary. Hypothalamic- hypophyseal tract Posterior lobe of pituitary

59 © 2013 Pearson Education, Inc. Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). Slide 5 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). Oxytocin and ADH are stored in axon terminals in the posterior pituitary. When hypothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood Oxytocin ADH Posterior lobe of pituitary Optic chiasma Infundibulum (connecting stalk) Axon terminals Paraventricular nucleus Hypothalamus Supraoptic nucleus Inferior hypophyseal artery Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary. Hypothalamic- hypophyseal tract Posterior lobe of pituitary

60 © 2013 Pearson Education, Inc. Pituitary-hypothalamic Relationships Anterior Lobe: –Originates as out-pocketing of oral mucosa –Vascular connection to hypothalamus Hypophyseal portal system –Primary capillary plexus –Hypophyseal portal veins –Secondary capillary plexus –Carries releasing and inhibiting hormones to anterior pituitary to regulate hormone secretion

61 © 2013 Pearson Education, Inc. Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2). Slide 1 Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary. In response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. This in turn empties into the general circulation. GH, TSH, ACTH, FSH, LH, PRL Anterior lobe of pituitary When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. Hypophyseal portal system Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus Superior hypophyseal artery Anterior lobe of pituitary Hypothalamus Hypothalamic neurons synthesize GHRH, GHIH, TRH, CRH, GnRH, PIH. A portal system is two capillary plexuses (beds) connected by veins

62 © 2013 Pearson Education, Inc. Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2). Slide 2 GH, TSH, ACTH, FSH, LH, PRL Anterior lobe of pituitary When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. Hypophyseal portal system Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus Superior hypophyseal artery Anterior lobe of pituitary Hypothalamus Hypothalamic neurons synthesize GHRH, GHIH, TRH, CRH, GnRH, PIH. A portal system is two capillary plexuses (beds) connected by veins. 1

63 © 2013 Pearson Education, Inc. Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2). Slide 3 Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary. GH, TSH, ACTH, FSH, LH, PRL Anterior lobe of pituitary When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. Hypophyseal portal system Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus Superior hypophyseal artery Anterior lobe of pituitary Hypothalamus Hypothalamic neurons synthesize GHRH, GHIH, TRH, CRH, GnRH, PIH. A portal system is two capillary plexuses (beds) connected by veins. 1 2

64 © 2013 Pearson Education, Inc. Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2). Slide 4 Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary. In response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. This in turn empties into the general circulation. GH, TSH, ACTH, FSH, LH, PRL Anterior lobe of pituitary When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. Hypophyseal portal system Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus Superior hypophyseal artery Anterior lobe of pituitary Hypothalamus Hypothalamic neurons synthesize GHRH, GHIH, TRH, CRH, GnRH, PIH. A portal system is two capillary plexuses (beds) connected by veins

65 © 2013 Pearson Education, Inc. Posterior Pituitary and Hypothalamic Hormones Oxytocin and ADH –Each composed of nine amino acids –Almost identical – differ in two amino acids

66 © 2013 Pearson Education, Inc. Oxytocin Strong stimulant of uterine contraction Released during childbirth Hormonal trigger for milk ejection Acts as neurotransmitter in brain

67 © 2013 Pearson Education, Inc. ADH (Vasopressin) Inhibits or prevents urine formation Regulates water balance Targets kidney tubules reabsorb more water Release also triggered by pain, low blood pressure, and drugs Inhibited by alcohol, diuretics High concentrations vasoconstriction

68 © 2013 Pearson Education, Inc. ADH Diabetes insipidus –ADH deficiency due to hypothalamus or posterior pituitary damage –Must keep well-hydrated Syndrome of inappropriate ADH secretion (SIADH) –Retention of fluid, headache, disorientation –Fluid restriction; blood sodium level monitoring

69 © 2013 Pearson Education, Inc. Anterior Pituitary Hormones Growth hormone (GH) Thyroid-stimulating hormone (TSH) or thyrotropin Adrenocorticotropic hormone (ACTH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Prolactin (PRL)

70 © 2013 Pearson Education, Inc. Anterior Pituitary Hormones All are proteins All except GH activate cyclic AMP second- messenger systems at their targets TSH, ACTH, FSH, and LH are all tropic hormones (regulate secretory action of other endocrine glands)

71 © 2013 Pearson Education, Inc. Growth Hormone (GH, or Somatotropin) Produced by somatotropic cells Direct actions on metabolism –Increases blood levels of fatty acids; encourages use of fatty acids for fuel; protein synthesis –Decreases rate of glucose uptake and metabolism – conserving glucose – Glycogen breakdown and glucose release to blood (anti-insulin effect)

72 © 2013 Pearson Education, Inc. Growth Hormone (GH, or Somatotropin) Indirect actions on growth Mediates growth via growth-promoting proteins – insulin-like growth factors (IGFs) IGFs stimulate –Uptake of nutrients DNA and proteins –Formation of collagen and deposition of bone matrix Major targetsbone and skeletal muscle

73 © 2013 Pearson Education, Inc. Growth Hormone (GH) GH release chiefly regulated by hypothalamic hormones –Growth hormone–releasing hormone (GHRH) Stimulates release –Growth hormone–inhibiting hormone (GHIH) (somatostatin) Inhibits release Ghrelin (hunger hormone) also stimulates release

74 © 2013 Pearson Education, Inc. Homeostatic Imbalances of Growth Hormone Hypersecretion –In children results in gigantism –In adults results in acromegaly Hyposecretion –In children results in pituitary dwarfism

75 © 2013 Pearson Education, Inc. Figure 16.6 Growth-promoting and metabolic actions of growth hormone (GH). Hypothalamus secretes growth hormone–releasing hormone (GHRH), and GHIH (somatostatin) Anterior pituitary Inhibits GHRH release Stimulates GHIH release Inhibits GH synthesis and release Feedback Indirect actions (growth- promoting) Liver and other tissues Insulin-like growth factors (IGFs) Produce Effects Skeletal Extraskeletal Fat metabolism Carbohydrate metabolism Direct actions (metabolic, anti-insulin) Effects Growth hormone (GH) Increased cartilage formation and skeletal growth Increased protein synthesis, and cell growth and proliferation Increased fat breakdown and release Increased blood glucose and other anti-insulin effects Increases, stimulates Initial stimulus Reduces, inhibits Physiological response Result

76 © 2013 Pearson Education, Inc. Figure 16.7 Disorders of pituitary growth hormone.

77 © 2013 Pearson Education, Inc. Thyroid-stimulating Hormone (Thyrotropin) Produced by thyrotropic cells of anterior pituitary Stimulates normal development and secretory activity of thyroid Release triggered by thyrotropin-releasing hormone from hypothalamus Inhibited by rising blood levels of thyroid hormones that act on pituitary and hypothalamus

78 © 2013 Pearson Education, Inc. Hypothalamus TRH Anterior pituitary TSH Thyroid gland Thyroid hormones Target cells Stimulates Figure 16.8 Regulation of thyroid hormone secretion. Inhibits

79 © 2013 Pearson Education, Inc. Adrenocorticotropic Hormone (Corticotropin) Secreted by corticotropic cells of anterior pituitary Stimulates adrenal cortex to release corticosteroids

80 © 2013 Pearson Education, Inc. Adrenocorticotropic Hormone (Corticotropin) Regulation of ACTH release –Triggered by hypothalamic corticotropin- releasing hormone (CRH) in daily rhythm –Internal and external factors such as fever, hypoglycemia, and stressors can alter release of CRH

81 © 2013 Pearson Education, Inc. Gonadotropins Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Secreted by gonadotrophs of anterior pituitary FSH stimulates gamete (egg or sperm) production LH promotes production of gonadal hormones Absent from the blood in prepubertal boys and girls

82 © 2013 Pearson Education, Inc. Gonadotropins Regulation of gonadotropin release –Triggered by gonadotropin-releasing hormone (GnRH) during and after puberty –Suppressed by gonadal hormones (feedback)

83 © 2013 Pearson Education, Inc. Prolactin (PRL) Secreted by prolactin cells of anterior pituitary Stimulates milk production Role in males not well understood

84 © 2013 Pearson Education, Inc. Prolactin (PRL) Regulation of PRL release –Primarily controlled by prolactin-inhibiting hormone (PIH) (dopamine) Blood levels rise toward end of pregnancy Suckling stimulates PRL release and promotes continued milk production Hypersecretion causes inappropriate lactation, lack of menses, infertility in females, and impotence in males


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