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PowerPoint ® Lecture Slides prepared by Janice Meeking, Mount Royal College C H A P T E R Copyright © 2010 Pearson Education, Inc. 16 The Endocrine System:

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Presentation on theme: "PowerPoint ® Lecture Slides prepared by Janice Meeking, Mount Royal College C H A P T E R Copyright © 2010 Pearson Education, Inc. 16 The Endocrine System:"— Presentation transcript:

1 PowerPoint ® Lecture Slides prepared by Janice Meeking, Mount Royal College C H A P T E R Copyright © 2010 Pearson Education, Inc. 16 The Endocrine System: Part A

2 Copyright © 2010 Pearson Education, Inc. Figure 16.1 Pineal gland Hypothalamus Pituitary gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Thyroid gland Adrenal glands Pancreas Ovary (female) Testis (male)

3 Copyright © 2010 Pearson Education, Inc. Endocrine System: Overview Endo = within Crine = to secrete Endocrine glands are ductless glands, secrete into blood stream Exocrine glands are glands with ducts, secrete out of the body (generally) Endocrine glands: pancreas, pineal, hypothalamus, pituitary, thyroid, parathyroid, and adrenal glands, and ovaries and testes

4 Copyright © 2010 Pearson Education, Inc. Endocrine System: Overview Definition: ductless glands and tissues that secrete hormones which influence metabolic activities Hormones are long distance chemical signals that travel in blood and lymph

5 Copyright © 2010 Pearson Education, Inc. Endocrine System: Overview Hormones Regulate growth and development Regulate cellular metabolism and energy balance Regulate reproduction Mobilize the immune system Maintain balance of electrolytes, water, and nutrients in the blood

6 Copyright © 2010 Pearson Education, Inc. Other tissues and organs that produce hormones include: adipose cells thymus cells in the walls of the small intestine stomach kidneys heart Endocrine System: Overview

7 Copyright © 2010 Pearson Education, Inc. Endocrine System: Overview Some organs produce both endocrine (hormones) and exocrine products (secretions into ducts) e.g., pancreas and gonads Some glands have both nervous and endocrine function e.g., the hypothalamus and adrenal glands

8 Copyright © 2010 Pearson Education, Inc. Endocrine System: Overview Comparison of Endocrine and Nervous System

9 Copyright © 2010 Pearson Education, Inc. Together, they coordinate functions of all body systems. - Both send chemical signals - Both affect specific target organs or tissues - Both work to maintain Homeostasis in the body NERVOUS SYSTEM VS. ENDOCRINE SYSTEM NERVOUS neurotransmitters hormones ENDOCRINE muscle contractions and glandular secretions metabolic activities of cells acts in milliseconds acts in seconds to minutes to hours to days to months brief effects long-lasting effects

10 Copyright © 2010 Pearson Education, Inc. Nervous System vs. Endocrine System Together the nervous and endocrine systems coordinate functions of all body systems. The nervous system controls homeostasis through nerve impulses (action potentials) conducted along axons of neurons. In contrast, the endocrine system releases its hormones into the bloodstream. The circulating blood then delivers hormones to virtually all cells throughout the body. Certain parts of the nervous system stimulate or inhibit the release of hormones. Hormones in turn may promote or inhibit the generation of nerve impulses. (Nervous and Endocrine interact!)

11 Copyright © 2010 Pearson Education, Inc. Nervous System Modulation The nervous system can override normal endocrine controls For example, control of blood glucose levels Normally the endocrine system maintains blood glucose Under stress, the body needs more glucose The hypothalamus and the sympathetic nervous system are activated to supply ample glucose

12 Copyright © 2010 Pearson Education, Inc. Endocrine action: the hormone is distributed in blood and binds to distant target cells. Paracrine action: the hormone acts locally by diffusing from its source to target cells in the neighborhood. Autocrine action: the hormone acts on the same cell that produced it. Endocrine System: Overview

13 Copyright © 2010 Pearson Education, Inc. Classes of Hormones Two main classes 1.Amino acid-based hormones Amines, thyroxine (T4), peptides, and proteins Insulin! 2.Steroids Synthesized from cholesterol Gonadal and adrenocortical hormones

14 Copyright © 2010 Pearson Education, Inc. Hormone Classification All steroid hormones are made initially from the precursor cholesterol.

15 Copyright © 2010 Pearson Education, Inc. Steroid hormone synthesis from cholesterol Important steroid end products: Aldosterone Cortisol DHEA Testosterone Estrone (E3) and Estraidol (E2)

16 Copyright © 2010 Pearson Education, Inc. Mechanisms of Hormone Action Hormone action on target cells 1.Alter plasma membrane permeability of membrane potential by opening or closing ion channels 2.Stimulate synthesis of proteins or regulatory molecules 3.Activate or deactivate enzyme systems 4.Induce secretory activity 5.Stimulate mitosis

17 Copyright © 2010 Pearson Education, Inc. Mechanisms of Hormone Action Two mechanisms, depending on their chemical nature 1.Water-soluble hormones (all amino acid–based hormones except thyroid hormone) Act on plasma membrane receptors Cannot enter the target cells (hydrophilic molecules trying to pass through a hydrophobic membrane) Use second messenger systems to get message to target cell

18 Copyright © 2010 Pearson Education, Inc. Water-soluble hormones Mechanisms Of Water-Soluble Hormone Action catecholamine, peptide, and protein hormones target cells use membrane-bound receptors first messenger vs. second messenger G protein  adenylate cyclase  cyclic AMP  protein kinase phosphodiesterase 5’-AMP (inactive) phosphodiesterase adenylate cyclase hormone nucleus cAMP receptor G protein protein kinase altered cell function ATP converted to

19 Copyright © 2010 Pearson Education, Inc. Figure 16.2 Hormone (1st messenger) binds receptor. Receptor activates G protein (G S ). G protein activates adenylate cyclase. cAMP acti- vates protein kinases. Adenylate cyclase converts ATP to cAMP (2nd messenger). Receptor G protein (G S ) Adenylate cyclase Triggers responses of target cell (activates enzymes, stimulates cellular secretion, opens ion channel, etc.) Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Inactive protein kinase Extracellular fluid Cytoplasm Active protein kinase GDP Glucagon PTH TSH Calcitonin

20 Copyright © 2010 Pearson Education, Inc. Water Soluble Hormones Glucagon Insulin PTH TSH Calcitonin Epinephrine ACTH FSH LH

21 Copyright © 2010 Pearson Education, Inc. Second Messenger Systems 2 main types: cAMP (cyclic AMP) PIP 2 -calcium signaling mechanism Involves calcium!

22 Copyright © 2010 Pearson Education, Inc. Mechanisms of Hormone Action 2.Lipid-soluble hormones (steroid and thyroid hormones) Act on intracellular receptors that directly activate genes Hydrophobic molecule can pass across hydrophobic membrane

23 Copyright © 2010 Pearson Education, Inc. Lipid-soluble hormones Mechanisms Of Steroid Hormone Action steroid and thyroid hormones target cells use intracellular receptors hormone-receptor complexes altered gene expression hormone target cell nucleus DNA receptor diffusion hormone target cell protein mRNA hormone binds to receptor, which translocates to gene diffusion

24 Copyright © 2010 Pearson Education, Inc. Intracellular Receptors and Direct Gene Activation Steroid hormones and thyroid hormone 1.Diffuse into their target cells and bind with intracellular receptors 2.Receptor-hormone complex enters the nucleus 3.Receptor-hormone complex binds to a specific region of DNA 4.This prompts DNA transcription to produce mRNA 5.The mRNA directs protein synthesis

25 Copyright © 2010 Pearson Education, Inc. Target Cell Specificity Target cells must have specific receptors for the hormones to bind to the cell ACTH receptors are only found on certain cells of the adrenal cortex Thyroxine (T4) receptors are found on nearly all cells of the body

26 Copyright © 2010 Pearson Education, Inc. Target Cell Activation Target cell activation depends on three factors 1.Blood levels of the hormone 2.Relative number of receptors on or in the target cell 3.Affinity of binding between receptor and hormone

27 Copyright © 2010 Pearson Education, Inc. Target Cell Activation Hormones influence the number of their receptors Up-regulation—target cells form more receptors in response to the hormone Down-regulation—target cells lose receptors in response to the hormone

28 Copyright © 2010 Pearson Education, Inc. Hormones in the Blood Hormones circulate in the blood either free or bound Steroids and thyroid hormone are attached to plasma proteins (hydrophobic molecules need escorts through a hydrophilic environment) All others circulate without carriers (they are water soluble) The concentration of a circulating hormone reflects: Rate of release Speed of inactivation and removal from the body

29 Copyright © 2010 Pearson Education, Inc. Hormones in the Blood Hormones are removed from the blood by Degrading enzymes Kidneys Liver Half-life—the time required for a substance’s blood level to decrease by half Water soluble hormones have the shortest half life

30 Copyright © 2010 Pearson Education, Inc. Interaction of Hormones at Target Cells Multiple hormones may interact in several ways Permissiveness: one hormone cannot exert its effects without another hormone being present Synergism: more than one hormone produces the same effects on a target cell Antagonism: one or more hormones opposes the action of another hormone

31 Copyright © 2010 Pearson Education, Inc. Control of Hormone Release Blood levels of hormones Are controlled by negative feedback systems Vary only within a narrow desirable range Hormones are synthesized and released in response to 1.Humoral stimuli (body) 2.Neural stimuli 3.Hormonal stimuli

32 Copyright © 2010 Pearson Education, Inc. Humoral Stimuli Changing blood levels of ions and nutrients directly stimulates secretion of hormones Example: Ca 2+ in the blood Declining blood Ca 2+ concentration stimulates the parathyroid glands to secrete PTH (parathyroid hormone) PTH causes Ca 2+ concentrations to rise and the stimulus is removed

33 Copyright © 2010 Pearson Education, Inc. Figure 16.4a (a) Humoral Stimulus Capillary (low Ca 2+ in blood) Parathyroid glands Thyroid gland (posterior view) PTH Parathyroid glands 1 Capillary blood contains low concentration of Ca 2+, which stimulates… 2 …secretion of parathyroid hormone (PTH) by parathyroid glands*

34 Copyright © 2010 Pearson Education, Inc. Neural Stimuli Nerve fibers stimulate hormone release Sympathetic nervous system fibers stimulate the adrenal medulla to secrete catecholamines

35 Copyright © 2010 Pearson Education, Inc. Hormonal Stimuli Hormones stimulate other endocrine organs to release their hormones Hypothalamic hormones stimulate the 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 the final target organs inhibit the release of the anterior pituitary hormones

36 Copyright © 2010 Pearson Education, Inc. Figure 16.4c (c) Hormonal Stimulus Hypothalamus Thyroid gland Adrenal cortex Gonad (Testis) Pituitary gland 1 The hypothalamus secretes hormones that… 2 …stimulate the anterior pituitary gland to secrete hormones that… 3 …stimulate other endocrine glands to secrete hormones

37 Copyright © 2010 Pearson Education, Inc. Pineal Gland

38 Copyright © 2010 Pearson Education, Inc. Pineal Gland

39 Copyright © 2010 Pearson Education, Inc. Pineal Gland Small gland hanging from the roof of the third ventricle Pinealocytes secrete melatonin, derived from serotonin Melatonin may affect Timing of sexual maturation and puberty Day/night cycles Physiological processes that show rhythmic variations (body temperature, sleep, appetite)

40 Copyright © 2010 Pearson Education, Inc. Circadian Rhythm

41 Copyright © 2010 Pearson Education, Inc. Adrenal Ovary/ TestesThyroid Pituitary Hypothalamus PINEAL

42 Copyright © 2010 Pearson Education, Inc. Hypothalamus

43 Copyright © 2010 Pearson Education, Inc. Hypothalamus In the lower central part of the brain The main link between the endocrine and the nervous systems. Nerve cells in the hypothalamus control the pituitary gland by producing chemicals that either stimulate or suppress hormone secretions from the pituitary.

44 Copyright © 2010 Pearson Education, Inc. Hypothalamic Hormones GnRH (gonadotrophic releasing hormone) SS (somatostatin) PRF (prolactin releasing factor) PIH (prolactin releasing inhibiting hormone) TRH (thyrotrophin releasing hormone) CRH (corticotrophin releasing hormone) GHRH (growth hormone releasing hormone)

45 Copyright © 2010 Pearson Education, Inc. Hypothalamic Hormones Hormones from Hypothalamus

46 Copyright © 2010 Pearson Education, Inc. Pituitary Gland

47 Copyright © 2010 Pearson Education, Inc. Size of a pea Located at the base of the brain, and the most important part of the entire endocrine system. AKA: The master gland because it makes hormones that control other endocrine glands. The production of hormones and secretions can be affected by emotions and seasons change. Pituitary Gland

48 Copyright © 2010 Pearson Education, Inc. Pituitary Gland Pituitary gland and hypothalamus are connected via a stalk, also known as the infundibulum.

49 Copyright © 2010 Pearson Education, Inc. Pituitary Gland The pituitary gland (hypophysis) has two major lobes 1.Posterior pituitary (lobe) (neurohypophysis) Neural tissue Neuro = nervous 2.Anterior pituitary (lobe) (adenohypophysis) Glandular tissue Adeno = gland

50 Copyright © 2010 Pearson Education, Inc. Pituitary-Hypothalamic Relationships Posterior lobe A downgrowth of hypothalamic neural tissue Neural connection to the hypothalamus (hypothalamic-hypophyseal tract) Nuclei of the hypothalamus synthesize the neurohormones oxytocin and antidiuretic hormone (ADH) Neurohormones are transported to the posterior pituitary

51 Copyright © 2010 Pearson Education, Inc. Figure 16.5a Hypothalamic neurons synthesize oxytocin and ADH. Oxytocin and ADH are transported along the hypothalamic-hypophyseal tract to the posterior pituitary. Oxytocin and ADH are stored in axon terminals in the posterior pituitary. Oxytocin and ADH are released into the blood when hypothalamic neurons fire. Paraventricular nucleus Supraoptic nucleus Optic chiasma Hypothalamus Inferior hypophyseal artery Oxytocin ADH Infundibulum (connecting stalk) Hypothalamic- hypophyseal tract Axon terminals Posterior lobe of pituitary (a) Relationship between the posterior pituitary and the hypothalamus

52 Copyright © 2010 Pearson Education, Inc. Pituitary-Hypothalamic Relationships Anterior Lobe: Originates as an out-pocketing of the oral mucosa Anterior pituitary hormones travel through the blood to get from the hypothalamus to the pituitary; posterior pituitary hormones travel directly down neurons connecting the hypothalamus and pituitary Blood route = Hypophyseal portal system

53 Copyright © 2010 Pearson Education, Inc. Figure 16.5b When appropriately stimulated, hypothalamic neurons secrete releasing and inhibiting hormones into the primary capillary plexus. Hypothalamic hormones travel through the portal veins to the anterior pituitary where they stimulate or inhibit release of hormones from the anterior pituitary. Anterior pituitary hormones are secreted into the secondary capillary plexus. Hypothalamus Hypothalamic neuron cell bodies Hypophyseal portal system Superior hypophyseal artery (b) Relationship between the anterior pituitary and the hypothalamus Anterior lobe of pituitary TSH, FSH, LH, ACTH, GH, PRL Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus

54 Copyright © 2010 Pearson Education, Inc. Anterior Pituitary (adenohypophosis)

55 Copyright © 2010 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)

56 Copyright © 2010 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 the secretory action of other endocrine glands)

57 Copyright © 2010 Pearson Education, Inc. Target Organ Hypothalamus ? Short Loop Feedback Pituitary Long Loop Feedback Feedback Regulation of the Anterior Pituitary:

58 Copyright © 2010 Pearson Education, Inc. Growth Hormone (GH)

59 Copyright © 2010 Pearson Education, Inc. Growth Hormone (GH) Produced by somatotrophs Stimulates most cells, but targets bone and skeletal muscle Promotes protein synthesis and encourages use of fats for fuel (lipolysis or breakdown of fats) Most effects are mediated indirectly by insulin- like growth factors (IGFs) elevates blood glucose by decreasing glucose uptake and encouraging glycogen breakdown (anti-insulin effect of GH)

60 Copyright © 2010 Pearson Education, Inc. Growth Hormone (GH) GH release is regulated by Growth hormone–releasing hormone (GHRH) Growth hormone–inhibiting hormone (GHIH) (somatostatin)

61 Copyright © 2010 Pearson Education, Inc. Growth Hormone Actions: GH GHRHSomatostatin IGF-1 Insulin Antagonism Growth Lipolysis Growth Insulin Antagonism - + +

62 Copyright © 2010 Pearson Education, Inc. Figure 16.6 Growth hormone Feedback Inhibits GHRH release Stimulates GHIH release Inhibits GH synthesis and release Anterior pituitary Liver and other tissues Indirect actions (growth- promoting) Direct actions (metabolic, anti-insulin) Insulin-like growth factors (IGFs) Extraskeletal SkeletalFat Carbohydrate metabolism 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 Effects Produce Hypothalamus secretes growth hormone—releasing hormone (GHRH), and somatostatin (GHIH) Initial stimulus Physiological response Result Increases, stimulates Reduces, inhibits

63 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of Growth Hormone Hypersecretion In children results in gigantism Bone added on before growth plates close, person is very very tall/large In adults results in acromegaly Bone added after growth plates close, person accumulates extra bone, especially at feet, hands, face Hyposecretion In children results in pituitary dwarfism Not enough growth hormone to fully grow

64 Copyright © 2010 Pearson Education, Inc. Thyroid Stimulating Hormone (TSH)

65 Copyright © 2010 Pearson Education, Inc. Thyroid-Stimulating Hormone (Thyrotropin) Produced by thyrotrophs of the anterior pituitary Stimulates the normal development and secretory activity of the thyroid

66 Copyright © 2010 Pearson Education, Inc. Thyroid-Stimulating Hormone (Thyrotropin) Regulation of TSH release Stimulated by thyrotropin-releasing hormone (TRH) Inhibited by rising blood levels of thyroid hormones that act on the pituitary and hypothalamus

67 Copyright © 2010 Pearson Education, Inc. Figure 16.7 Hypothalamus Anterior pituitary Thyroid gland Thyroid hormones TSH TRH Target cells Stimulates Inhibits

68 Copyright © 2010 Pearson Education, Inc. Adrenocorticotrophic Hormone (ACTH)

69 Copyright © 2010 Pearson Education, Inc. Adrenocorticotropic Hormone (Corticotropin) Secreted by corticotrophs of the anterior pituitary Stimulates the adrenal cortex to release corticosteroids

70 Copyright © 2010 Pearson Education, Inc. Adrenocorticotropic Hormone (Corticotropin) Regulation of ACTH release Triggered by hypothalamic corticotropin- releasing hormone (CRH) in a daily rhythm Internal and external factors such as fever, hypoglycemia, and stressors can alter the release of CRH

71 Copyright © 2010 Pearson Education, Inc. Gonadotropins (FSH, LH)

72 Copyright © 2010 Pearson Education, Inc. Gonadotropins Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Secreted by gonadotrophs of the anterior pituitary FSH stimulates gamete (egg or sperm) production LH promotes production of gonadal hormones Absent from the blood in prepubertal boys and girls

73 Copyright © 2010 Pearson Education, Inc. Gonadotropins Regulation of gonadotropin release Triggered by the gonadotropin-releasing hormone (GnRH) during and after puberty Suppressed by gonadal hormones (feedback)

74 Copyright © 2010 Pearson Education, Inc. Prolactin (PRL)

75 Copyright © 2010 Pearson Education, Inc. Prolactin (PRL) Secreted by lactotrophs of the anterior pituitary Stimulates milk production

76 Copyright © 2010 Pearson Education, Inc. Prolactin (PRL) Regulation of PRL release Primarily controlled by prolactin-inhibiting hormone (PIH) (dopamine) Blood levels rise toward the end of pregnancy Suckling stimulates PRH release and promotes continued milk production

77 Copyright © 2010 Pearson Education, Inc. Posterior Pituitary (neurohypophosis)

78 Copyright © 2010 Pearson Education, Inc. The Posterior Pituitary Contains axons of hypothalamic neurons Stores antidiuretic hormone (ADH) and oxytocin ADH and oxytocin are released in response to nerve impulses Both use PIP-calcium second-messenger mechanism at their targets

79 Copyright © 2010 Pearson Education, Inc. Oxytocin

80 Copyright © 2010 Pearson Education, Inc. Oxytocin Stimulates uterine contractions during childbirth by mobilizing Ca 2+ through a PIP 2 - Ca 2+ second-messenger system Also triggers milk ejection (“letdown” reflex) in women producing milk Plays a role in sexual arousal and orgasm in males and females

81 Copyright © 2010 Pearson Education, Inc. Antidiuretic Hormone (ADH)

82 Copyright © 2010 Pearson Education, Inc. Antidiuretic Hormone (ADH) Hypothalamic osmoreceptors respond to changes in the solute concentration of the blood If solute concentration is high Osmoreceptors depolarize and transmit impulses to hypothalamic neurons ADH is synthesized and released, inhibiting urine formation

83 Copyright © 2010 Pearson Education, Inc. Antidiuretic Hormone (ADH) If solute concentration is low ADH is not released, allowing water loss Alcohol inhibits ADH release and causes copious urine output ADH’s job is to conserve water

84 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of ADH ADH deficiency—diabetes insipidus; huge output of urine and intense thirst ADH hypersecretion (after neurosurgery, trauma, or secreted by cancer cells)— syndrome of inappropriate ADH secretion (SIADH)

85 Copyright © 2010 Pearson Education, Inc. Thyroid Gland Hormones

86 Copyright © 2010 Pearson Education, Inc. The thyroid, shaped like a butterfly, produces thyroxine (T4) and triiodothyronine (T3). These control the rate at which cells burn fuels from food to produce energy. Thyroid hormones are important because they participate in the growth and development of kids’ and teens’ bones and the nervous system. Attached to the thyroid are the four parathyroids, which, with the help of calcitonin, control the calcium level. Thyroid

87 Copyright © 2010 Pearson Education, Inc. Figure 16.8

88 Copyright © 2010 Pearson Education, Inc. Thyroid Gland Consists of two lateral lobes connected by a median mass called the isthmus Composed of follicles that produce the glycoprotein thyroglobulin Colloid (thyroglobulin + iodine) fills the lumen of the follicles and is the precursor of thyroid hormone Parafollicular cells produce the hormone calcitonin

89 Copyright © 2010 Pearson Education, Inc. Thyroid Hormone Major metabolic hormone Increases metabolic rate and heat production (calorigenic effect) Plays a role in Maintenance of blood pressure Regulation of tissue growth Development of skeletal and nervous systems Reproductive capabilities

90 Copyright © 2010 Pearson Education, Inc. Thyroid Hormone (TH) Actually two related compounds T 4 (thyroxine); has 2 tyrosine molecules + 4 bound iodine atoms T 3 (triiodothyronine); has 2 tyrosines + 3 bound iodine atoms Majority of circulating hormone is T % T 4 1.5% T 3 for thyroid hormone to be built, it requires iodine

91 Copyright © 2010 Pearson Education, Inc. Transport and Regulation of TH T 4 and T 3 are transported by thyroxine-binding globulins (TBGs) Both bind to target receptors, but T 3 is ten times more active than T 4 Peripheral tissues convert T 4 to T 3 T 3 is more metabolically active than T 4

92 Copyright © 2010 Pearson Education, Inc. Transport and Regulation of TH Negative feedback regulation of TH release Rising TH levels provide negative feedback inhibition on release of TSH Hypothalamic thyrotropin-releasing hormone (TRH) can overcome the negative feedback during pregnancy or exposure to cold

93 Copyright © 2010 Pearson Education, Inc. Figure 16.7 Hypothalamus Anterior pituitary Thyroid gland Thyroid hormones TSH TRH Target cells Stimulates Inhibits

94 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of TH Hyposecretion in adults Hypothyroidism; very common, often the adrenals need to be supported and the thyroid will correct Sxs: weight gain, fatigue, hair brittle and dry/loss, constipation, depression, cold intolerance (all signs the metabolism is slow) endemic goiter if due to lack of iodine myxedema: very, very scary; end stage of hypothyroidism; dangerously low levels over a long period of time Bags under eyes very puffy, thyroid may be puffy, severe fatigue; person on the verge of collapse, can get fluid in lungs and fall into a coma

95 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of TH Hyposecretion in infants—cretinism Hypersecretion—Graves’ disease Opposite of hypothyroidism Racing heart/palpitations, anxiety, jitteriness, sweating, pupil dilation, weight loss Over long term, get bulging eyes Can see these effects in someone who has been rxed too much thyroid hormone

96 Copyright © 2010 Pearson Education, Inc. Figure 16.10

97 Copyright © 2010 Pearson Education, Inc. Calcitonin Produced by parafollicular (C) cells Antagonist to parathyroid hormone (PTH) Inhibits osteoclast activity and release of Ca 2+ from bone matrix Ca 2+ goes from blood to bone; lowers Ca 2+ levels in the blood No important role in humans; removal of thyroid (and its C cells) does not affect Ca 2+ homeostasis

98 Copyright © 2010 Pearson Education, Inc. Parathyroid Gland Hormones

99 Copyright © 2010 Pearson Education, Inc. Parathyroid Glands Four to eight tiny glands embedded in the posterior aspect of the thyroid chief cells secrete parathyroid hormone (PTH) PTH—most important hormone in Ca 2+ homeostasis Ca 2+ moves from bone to blood; increases blood levels of Ca 2+

100 Copyright © 2010 Pearson Education, Inc. Figure (b) Capillary Chief cells (secrete parathyroid hormone) Oxyphil cells Pharynx (posterior aspect) Thyroid gland Parathyroid glands Trachea Esophagus (a)

101 Copyright © 2010 Pearson Education, Inc. Parathyroid Hormone Functions Stimulates osteoclasts to digest bone matrix Enhances reabsorption of Ca 2+ and secretion of phosphate by the kidneys Promotes activation of vitamin D (by the kidneys); increases absorption of Ca 2+ by intestinal mucosa Negative feedback control: rising Ca 2+ in the blood inhibits PTH release

102 Copyright © 2010 Pearson Education, Inc. Parathyroid Hormone

103 Copyright © 2010 Pearson Education, Inc. Figure Intestine Kidney Bloodstream Hypocalcemia (low blood Ca 2+ ) stimulates parathyroid glands to release PTH. Rising Ca 2+ in blood inhibits PTH release. 1 PTH activates osteoclasts: Ca 2+ and PO 4 3S released into blood. 2 PTH increases Ca 2+ reabsorption in kidney tubules. 3 PTH promotes kidney’s activation of vitamin D, which increases Ca 2+ absorption from food. Bone Ca 2+ ions PTH Molecules

104 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of PTH Hyperparathyroidism due to tumor Bones soften and deform Elevated Ca 2+ depresses the nervous system and contributes to formation of kidney stones Hypoparathyroidism following gland trauma or removal Results in tetany, respiratory paralysis, and death

105 Copyright © 2010 Pearson Education, Inc. Adrenal Gland Hormones

106 Copyright © 2010 Pearson Education, Inc. Adrenal (Suprarenal) Glands Paired, pyramid-shaped organs atop the kidneys Structurally and functionally, they are two glands in one Adrenal medulla—nervous tissue; part of the sympathetic nervous system (short term stress) Adrenal cortex—three layers of glandular tissue that synthesize and secrete corticosteroids (long term stress)

107 Copyright © 2010 Pearson Education, Inc. Adrenal Cortex Three layers and the corticosteroids produced Zona glomerulosa—mineralocorticoids Zona fasciculata—glucocorticoids Zona reticularis—sex hormones, or gonadocorticoids G: Salt F: Sugar R: Sex

108 Copyright © 2010 Pearson Education, Inc. Figure 16.13a Cortex Kidney Medulla Adrenal gland Capsule Zona glomerulosa Zona fasciculata Zona reticularis Adrenal medulla (a) Drawing of the histology of the adrenal cortex and a portion of the adrenal medulla Medulla Cortex

109 Copyright © 2010 Pearson Education, Inc. Mineralocorticoids: Zona Glomerulosa Regulate electrolytes (primarily Na + and K + ) in ECF Importance of Na + : affects ECF volume, blood volume, blood pressure, levels of other ions Importance of K + : sets RMP of cells Aldosterone is the most potent mineralocorticoid Stimulates Na + reabsorption and water retention by the kidneys

110 Copyright © 2010 Pearson Education, Inc. Hormones of the Adrenal Cortex

111 Copyright © 2010 Pearson Education, Inc. Mechanisms of Aldosterone Secretion 1.Renin-angiotensin mechanism: decreased blood pressure stimulates kidneys to release renin, triggers formation of angiotensin II, a potent stimulator of aldosterone release 2.Plasma concentration of K + : Increased K + directly influences the zona glomerulosa cells to release aldosterone 3.ACTH: causes small increases of aldosterone during stress 4.Atrial natriuretic peptide (ANP): blocks renin and aldosterone secretion, to decrease blood pressure

112 Copyright © 2010 Pearson Education, Inc. Figure Primary regulatorsOther factors Blood volume and/or blood pressure Angiotensin II Blood pressure and/or blood volume K + in blood Direct stimulating effect Renin Initiates cascade that produces Kidney Hypo- thalamus Heart CRH Anterior pituitary Zona glomerulosa of adrenal cortex Enhanced secretion of aldosterone Targets kidney tubules Absorption of Na + and water; increased K + excretion Blood volume and/or blood pressure Inhibitory effect Stress ACTH Atrial natriuretic peptide (ANP)

113 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of Aldosterone Aldosteronism—hypersecretion due to adrenal tumors Hypertension and edema due to excessive Na + Excretion of K + leading to abnormal function of neurons and muscle

114 Copyright © 2010 Pearson Education, Inc. Glucocorticoids (Cortisol): Zona Fasiculata Keep blood sugar levels relatively constant Maintain blood pressure by increasing the action of vasoconstrictors

115 Copyright © 2010 Pearson Education, Inc. Glucocorticoids (Cortisol) Cortisol is the most significant glucocorticoid Released in response to ACTH, patterns of eating and activity, and stress Prime metabolic effect is gluconeogenesis— formation of glucose from fats and proteins Promotes rises in blood glucose, fatty acids, and amino acids

116 Copyright © 2010 Pearson Education, Inc. Glucocorticoids: Cortisol Should be high at beginning of day and taper off; many people (especially students) have disrupted cortisol rhythms; stress hormone Cortisol suppresses the immune system If cortisol is high, more likely to get sick Same happens if taking corticosteriods (like prednisone or putting hydrocortisone cream on eczema)

117 Copyright © 2010 Pearson Education, Inc. Hormones of the Adrenal Cortex

118 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of Glucocorticoids Hypersecretion—Cushing’s syndrome Depresses cartilage and bone formation Inhibits inflammation Depresses the immune system Promotes changes in cardiovascular, neural, and gastrointestinal function Signs: Abdominal weight gain, thin skin, moon face, red cheeks, purple stripes, buffalo hump, Na/K levels in a bad ratio in labs Hyposecretion—Addison’s disease Also involves deficits in mineralocorticoids Decrease in glucose and Na + levels Weight loss, severe dehydration, and hypotension, tan skin

119 Copyright © 2010 Pearson Education, Inc. Figure 16.15

120 Copyright © 2010 Pearson Education, Inc. Hyper-adrenocorticism Cushing’s syndrome 3rd - 6th decade, 4 to1 females causes pharmocologic pituitary adenoma 75-90% adrenal adenoma, carcinoma ectopic ACTH treatment based on cause

121 Copyright © 2010 Pearson Education, Inc. Depressed secretion of glucocorticoids and mineralocorticoids S & S Weight loss Glucose and sodium in blood are low Rising blood levels of K + Dehydration and hypotension

122 Copyright © 2010 Pearson Education, Inc. Gonadocorticoids

123 Copyright © 2010 Pearson Education, Inc. Gonadocorticoids (Sex Hormones) Most are androgens (male sex hormones) that are converted to testosterone in tissue cells or estrogens in females DHEA is also produced, which is the precursor for androgens May contribute to The onset of puberty The appearance of secondary sex characteristics Sex drive

124 Copyright © 2010 Pearson Education, Inc. DHEA and Androgen production

125 Copyright © 2010 Pearson Education, Inc. Adrenal Medulla Nervous system tissue Chromaffin cells secrete epinephrine (80%) and norepinephrine (20%) These hormones cause Blood glucose levels to rise Blood vessels to constrict The heart to beat faster Blood to be diverted to the brain, heart, and skeletal muscle

126 Copyright © 2010 Pearson Education, Inc. Adrenal Medulla Epinephrine stimulates metabolic activities, bronchial dilation, and blood flow to skeletal muscles and the heart Norepinephrine influences peripheral vasoconstriction and blood pressure Both stimulate the fight or flight response or short term stress response

127 Copyright © 2010 Pearson Education, Inc. Figure Short-term stressMore prolonged stress Stress Hypothalamus CRH (corticotropin- releasing hormone) Corticotroph cells of anterior pituitary To target in blood Adrenal cortex (secretes steroid hormones) Glucocorticoids Mineralocorticoids ACTH Catecholamines (epinephrine and norepinephrine) Short-term stress response 1. Increased heart rate 2. Increased blood pressure 3. Liver converts glycogen to glucose and releases glucose to blood 4. Dilation of bronchioles 5. Changes in blood flow patterns leading to decreased digestive system activity and reduced urine output 6. Increased metabolic rate Long-term stress response 1. Retention of sodium and water by kidneys 2. Increased blood volume and blood pressure 1. Proteins and fats converted to glucose or broken down for energy 2. Increased blood glucose 3. Suppression of immune system Adrenal medulla (secretes amino acid- based hormones) Preganglionic sympathetic fibers Spinal cord Nerve impulses

128 Copyright © 2010 Pearson Education, Inc. Major Events in the General Stress Response

129 Copyright © 2010 Pearson Education, Inc. Pancreas Hormones

130 Copyright © 2010 Pearson Education, Inc. Pancreas

131 Copyright © 2010 Pearson Education, Inc. Pancreas Triangular gland behind the stomach Has both exocrine and endocrine cells Acinar cells (exocrine) produce an enzyme-rich juice for digestion Pancreatic islets (islets of Langerhans) contain endocrine cells Alpha (  ) cells produce glucagon (a hyperglycemic hormone) Beta (  ) cells produce insulin (a hypoglycemic hormone)

132 Copyright © 2010 Pearson Education, Inc. Figure Pancreatic islet (of Langerhans) (Glucagon- producing) cells (Insulin- producing) cells Pancreatic acinar cells (exocrine)

133 Copyright © 2010 Pearson Education, Inc. Glucagon Major target is the liver, where it promotes Glycogenolysis—breakdown of glycogen to glucose Gluconeogenesis—synthesis of glucose from lactic acid and noncarbohydrates Release of glucose into the blood; increases blood glucose levels

134 Copyright © 2010 Pearson Education, Inc. Insulin Effects of insulin Lowers blood glucose levels Enhances membrane transport of glucose into fat and muscle cells Participates in neuronal development and learning and memory Inhibits glycogenolysis and gluconeogenesis

135 Copyright © 2010 Pearson Education, Inc. Figure Liver Tissue cells Stimulates glucose uptake by cells Stimulates glycogen formation Pancreas Insulin Blood glucose falls to normal range. Stimulates glycogen breakdown Blood glucose rises to normal range. Glucagon Stimulus Blood glucose level Stimulus Blood glucose level Glycogen Glucose Glycogen Glucose

136 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of Insulin Diabetes mellitus (DM) Type I (juvenile) Due to hyposecretion of insulin Autoimmune cause (autoantibodies destroy beta cells of pancreas) Will initially cause weight loss Type II (adult onset) Due to hypoactivity of insulin; the cells may have become resistant to insulin from constant stimulation, or less sensitive (less receptors for insulin) Tendency toward obesity, unhealthy diet and lifestyle

137 Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of Insulin Three cardinal signs of DM Polyuria—huge urine output Body trying to get rid of excess glucose Polydipsia—excessive thirst Body trying to dilute high glucose in the blood Polyphagia—excessive hunger and food consumption Cells are starving because insulin is not transporting sugar into cells Hyperinsulinism: Excessive insulin secretion; results in hypoglycemia, disorientation, unconsciousness

138 Copyright © 2010 Pearson Education, Inc. Table 16.4

139 Copyright © 2010 Pearson Education, Inc. Gonadal Hormones

140 Copyright © 2010 Pearson Education, Inc. Ovaries and Placenta Gonads produce steroid sex hormones Ovaries produce estrogens and progesterone responsible for: Maturation of female reproductive organs Appearance of female secondary sexual characteristics Breast development and cyclic changes in the uterine mucosa The placenta secretes estrogens, progesterone, and human chorionic gonadotropin (hCG)

141 Copyright © 2010 Pearson Education, Inc. Testes Testes produce testosterone that Initiates maturation of male reproductive organs Causes appearance of male secondary sexual characteristics and sex drive Is necessary for normal sperm production Maintains reproductive organs in their functional state

142 Copyright © 2010 Pearson Education, Inc. Other Hormone Producing Tissues

143 Copyright © 2010 Pearson Education, Inc. Other Hormone-Producing Structures Heart Atrial natriuretic peptide (ANP) reduces blood pressure, blood volume, and blood Na + concentration Gastrointestinal tract enteroendocrine cells Gastrin from stomach stimulates release of HCl Secretin from SI stimulates liver and pancreas Cholecystokinin from SI stimulates pancreas, gallbladder, and hepatopancreatic sphincter

144 Copyright © 2010 Pearson Education, Inc. Other Hormone-Producing Structures Kidneys Erythropoietin signals production of red blood cells Renin initiates the renin-angiotensin mechanism Skin Cholecalciferol, the precursor of vitamin D Adipose tissue Leptin is involved in appetite control, and stimulates increased energy expenditure

145 Copyright © 2010 Pearson Education, Inc. Other Hormone-Producing Structures Skeleton (osteoblasts) Osteocalcin prods pancreatic beta cells to divide and secrete more insulin, improving glucose handling and reducing body fat Thymus Thymulin, thymopoietins, and thymosins are involved in normal the development of the T lymphocytes in the immune response

146 Copyright © 2010 Pearson Education, Inc. Developmental Aspects

147 Copyright © 2010 Pearson Education, Inc. Developmental Aspects Hormone-producing glands arise from all three germ layers Exposure to pesticides, industrial chemicals, arsenic, dioxin, BPA, plastics, and soil and water pollutants disrupts hormone function Sex hormones, thyroid hormone, and glucocorticoids are vulnerable to the effects of pollutants Interference with glucocorticoids may help explain high cancer rates in certain areas

148 Copyright © 2010 Pearson Education, Inc. Developmental Aspects Ovaries undergo significant changes with age and become unresponsive to gonadotropins; problems associated with estrogen deficiency begin to occur Testosterone also diminishes with age, but effect is not usually seen until very old age

149 Copyright © 2010 Pearson Education, Inc. Developmental Aspects GH levels decline with age and this accounts for muscle atrophy with age TH declines with age, contributing to lower basal metabolic rates PTH levels remain fairly constant with age, but lack of estrogen in older women makes them more vulnerable to bone-demineralizing effects of PTH

150 Copyright © 2010 Pearson Education, Inc. QUESTIONS TO TEST WHAT YOU NOW KNOW!!!

151 Copyright © 2010 Pearson Education, Inc. A major difference between neurotransmitters and hormones is that hormones are secreted ____________. A.directly onto their target cell B.into the cerebrospinal fluid C.into ducts D.into the blood

152 Copyright © 2010 Pearson Education, Inc. A major determinant of a hormone’s mechanism of action is __________. A.whether the hormonal molecule is hydrophobic or hydrophilic B.its size C.whether it is rapid acting or slow acting D.if it activates gene activity or not

153 Copyright © 2010 Pearson Education, Inc. Receptors for steroid hormones are commonly located _________. A.inside the target cell B.on the plasma membrane of the target cell C.in the blood plasma D.in the extracellular fluid

154 Copyright © 2010 Pearson Education, Inc. Interaction with a membrane-bound receptor will transmit the hormonal message via __________. A.depolarization B.direct gene activation C.a second messenger D.endocytosis

155 Copyright © 2010 Pearson Education, Inc. Which of the following molecules act as second messengers? A.cAMP B.Ca 2+ C.Na+ D.A and B

156 Copyright © 2010 Pearson Education, Inc. It’s possible for a steroid hormone and a protein hormone to affect the same intracellular protein because: A.the steroid hormone may direct the synthesis of the protein. B.the protein hormone may activate the protein. C.the protein hormone may direct the synthesis of the protein. D.of all of the above.

157 Copyright © 2010 Pearson Education, Inc. In order for a hormone to activate a target cell, the target cell must possess _______. A.a receptor B.a second messenger C.the hormone D.a chaperone

158 Copyright © 2010 Pearson Education, Inc. The most common form of endocrine malfunction is __________. A.failure of the gland to produce the hormone B.insensitivity of the target cell to the hormone C.overproduction of the hormone by the gland D.All of the above are common disorders.

159 Copyright © 2010 Pearson Education, Inc. When the pancreas releases insulin in direct response to blood glucose, this is an example of ________ stimulation. A.humoral B.neural C.hormonal D.negative feedback

160 Copyright © 2010 Pearson Education, Inc. When two people kiss, their neurohypophyses releases oxytocin. This is an example of __________ stimulation. A.humoral B.neural C.hormonal D.negative feedback

161 Copyright © 2010 Pearson Education, Inc. When the ovaries secrete estrogen in response to the hormone GnRH, this is an example of __________ stimulation. A.humoral B.neural C.hormonal D.negative feedback

162 Copyright © 2010 Pearson Education, Inc. Blood levels of hormone are kept within very narrow ranges by _________ mechanisms. A.humoral B.neural C.hormonal D.negative feedback

163 Copyright © 2010 Pearson Education, Inc. Hormones secreted into the hypophyseal portal system are delivered directly to the ________. A.neurohypophysis B.adenohypophysis C.median eminence D.infundibulum

164 Copyright © 2010 Pearson Education, Inc. A patient is displaying high volumes of urine output and severe dehydration. The most likely cause is _________. A.hyposecretion of oxytocin B.hypersecretion of oxytocin C.hyposecretion of ADH D.hypersecretion of ADH

165 Copyright © 2010 Pearson Education, Inc. Common secretion(s) of the thyroid gland is (are) _________. A.calcitonin B.Triiodothyronine (T 3 ) C.Thyroxine (T 4 ) D.all of the above

166 Copyright © 2010 Pearson Education, Inc. A patient is losing weight rapidly, sweating profusely, and is always anxious. The patient may be suffering from _______. A.hypothyroidism B.cretinism C.hyperthyroidism D.hypersecretion of calcitonin

167 Copyright © 2010 Pearson Education, Inc. Two hormones govern calcium regulation. ________ acts to elevate blood calcium levels, whereas ________ lowers blood calcium levels. A.PTH; calcitonin B.Thyroid hormones; calmodulin C.Calcitonin; PTH D.Calcitonin; thyroid hormone

168 Copyright © 2010 Pearson Education, Inc. __________ is the adrenal hormone responsible for maintaining appropriate blood sodium levels. A.Cortisol B.DHEA C.Aldosterone D.Epinephrine

169 Copyright © 2010 Pearson Education, Inc. _________ trigger(s) secretion of aldosterone. A.Increased K + B.Angiotensin II C.ANP D.Both a and b

170 Copyright © 2010 Pearson Education, Inc. During times of stress, elevated levels of _______ often occur, which explains why we get a cold during final exam time. A.cortisol B.aldosterone C.ACTH D.androgens

171 Copyright © 2010 Pearson Education, Inc. Along with the sympathetic nervous system, the _________ is the other primary mediator of acute stress. A.adrenal medulla B.adrenal cortex C.zona glomerulosa D.zona reticularis

172 Copyright © 2010 Pearson Education, Inc. The secretion of ________ helps regulate our circadian rhythms. A.estrogen B.testosterone C.thyroid hormones D.melatonin

173 Copyright © 2010 Pearson Education, Inc. The thymus secretes the hormone(s) ______________. A.thymopoietin B.thymosin C.thymic factor D.all of the above

174 Copyright © 2010 Pearson Education, Inc. Which of the following structures produces a hormone responsible for stimulating red blood cell production? A.Stomach B.Heart C.Kidney D.Skin

175 Copyright © 2010 Pearson Education, Inc. Which of the following structures produces a precursor to hormonal vitamin D, important for Ca 2+ regulation? A.Stomach B.Heart C.Kidney D.Skin


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