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The Endocrine System: Part A

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1 The Endocrine System: Part A
16 The Endocrine System: Part A

2 Pineal gland Hypothalamus Pituitary gland Thyroid gland
Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 16.1

3 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 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 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 Endocrine System: Overview
Other tissues and organs that produce hormones include: adipose cells thymus cells in the walls of the small intestine stomach kidneys heart

7 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 Endocrine System: Overview
Comparison of Endocrine and Nervous System

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 ENDOCRINE neurotransmitters hormones 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 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 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 Endocrine System: Overview
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.

13 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 Hormone Classification
All steroid hormones are made initially from the precursor cholesterol.

15 Steroid hormone synthesis from cholesterol
Important steroid end products: Aldosterone Cortisol DHEA Testosterone Estrone (E3) and Estraidol (E2)

16 Mechanisms of Hormone Action
Hormone action on target cells Alter plasma membrane permeability of membrane potential by opening or closing ion channels Stimulate synthesis of proteins or regulatory molecules Activate or deactivate enzyme systems Induce secretory activity Stimulate mitosis

17 Mechanisms of Hormone Action
Two mechanisms, depending on their chemical nature 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 Mechanisms Of Water-Soluble Hormone Action
Water-soluble hormones 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 Hormone (1st messenger) binds receptor. Extracellular fluid
Adenylate cyclase G protein (GS) 5 cAMP acti- vates protein kinases. Receptor GDP Inactive protein kinase Active protein kinase 2 Receptor activates G protein (GS). 3 G protein activates adenylate cyclase. Adenylate cyclase converts ATP to cAMP (2nd messenger). 4 Hormones that act via cAMP mechanisms: Triggers responses of target cell (activates enzymes, stimulates cellular secretion, opens ion channel, etc.) Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin Cytoplasm Figure 16.2

20 Water Soluble Hormones
Glucagon Insulin PTH TSH Calcitonin Epinephrine ACTH FSH LH

21 Second Messenger Systems
2 main types: cAMP (cyclic AMP) PIP2-calcium signaling mechanism Involves calcium!

22 Mechanisms of Hormone Action
Lipid-soluble hormones (steroid and thyroid hormones) Act on intracellular receptors that directly activate genes Hydrophobic molecule can pass across hydrophobic membrane

23 Mechanisms Of Steroid Hormone Action
Lipid-soluble hormones 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 Intracellular Receptors and Direct Gene Activation
Steroid hormones and thyroid hormone Diffuse into their target cells and bind with intracellular receptors Receptor-hormone complex enters the nucleus Receptor-hormone complex binds to a specific region of DNA This prompts DNA transcription to produce mRNA The mRNA directs protein synthesis

25 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 Target Cell Activation
Target cell activation depends on three factors Blood levels of the hormone Relative number of receptors on or in the target cell Affinity of binding between receptor and hormone

27 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 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 Hormones are removed from the blood by
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 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 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 Humoral stimuli (body) Neural stimuli Hormonal stimuli

32 Example: Ca2+ in the blood
Humoral Stimuli Changing blood levels of ions and nutrients directly stimulates secretion of hormones Example: Ca2+ in the blood Declining blood Ca2+ concentration stimulates the parathyroid glands to secrete PTH (parathyroid hormone) PTH causes Ca2+ concentrations to rise and the stimulus is removed

33 Capillary blood contains low concentration of Ca2+, which stimulates…
(a) Humoral Stimulus Capillary blood contains low concentration of Ca2+, which stimulates… 1 Capillary (low Ca2+ in blood) Thyroid gland (posterior view) Parathyroid glands Parathyroid glands PTH …secretion of parathyroid hormone (PTH) by parathyroid glands* 2 Figure 16.4a

34 Nerve fibers stimulate hormone release
Neural Stimuli Nerve fibers stimulate hormone release Sympathetic nervous system fibers stimulate the adrenal medulla to secrete catecholamines

35 Hormones stimulate other endocrine organs to release their hormones
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 The hypothalamus secretes hormones that…
(c) Hormonal Stimulus The hypothalamus secretes hormones that… 1 Hypothalamus …stimulate the anterior pituitary gland to secrete hormones that… 2 Pituitary gland Thyroid gland Adrenal cortex Gonad (Testis) …stimulate other endocrine glands to secrete hormones 3 Figure 16.4c

37 Pineal Gland

38 Pineal Gland

39 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 Circadian Rhythm

41 PINEAL Hypothalamus Pituitary Adrenal Ovary/ Testes Thyroid

42 Hypothalamus

43 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 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 Hypothalamic Hormones
Hormones from Hypothalamus

46 Pituitary Gland

47 Pituitary Gland 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.

48 Pituitary Gland Pituitary gland and hypothalamus are connected via a stalk, also known as the infundibulum.

49 The pituitary gland (hypophysis) has two major lobes
Posterior pituitary (lobe) (neurohypophysis) Neural tissue Neuro = nervous Anterior pituitary (lobe) (adenohypophysis) Glandular tissue Adeno = gland

50 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 Inferior hypophyseal artery
Hypothalamic neurons synthesize oxytocin and ADH. 1 Paraventricular nucleus Hypothalamus Supraoptic nucleus Oxytocin and ADH are transported along the hypothalamic-hypophyseal tract to the posterior pituitary. 2 Optic chiasma Infundibulum (connecting stalk) Inferior hypophyseal artery Hypothalamic- hypophyseal tract Oxytocin and ADH are stored in axon terminals in the posterior pituitary. 3 Axon terminals Oxytocin and ADH are released into the blood when hypothalamic neurons fire. 4 Posterior lobe of pituitary Oxytocin ADH (a) Relationship between the posterior pituitary and the hypothalamus Figure 16.5a

52 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 Hypothalamic hormones travel through the portal
Hypothalamus When appropriately stimulated, hypothalamic neurons secrete releasing and inhibiting hormones into the primary capillary plexus. 1 Hypothalamic neuron cell bodies Superior hypophyseal artery Hypophyseal portal system Hypothalamic hormones travel through the portal veins to the anterior pituitary where they stimulate or inhibit release of hormones from the anterior pituitary. 2 • Primary capillary plexus • Hypophyseal portal veins • Secondary capillary plexus Anterior lobe of pituitary Anterior pituitary hormones are secreted into the secondary capillary plexus. 3 TSH, FSH, LH, ACTH, GH, PRL (b) Relationship between the anterior pituitary and the hypothalamus Figure 16.5b

54 Anterior Pituitary (adenohypophosis)

55 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 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 ? + + Feedback Regulation of the Anterior Pituitary: - - - -
Hypothalamus - - Short Loop Feedback ? + - Long Loop Feedback - Pituitary + Target Organ

58 Growth Hormone (GH)

59 Produced by somatotrophs
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 GH release is regulated by
Growth Hormone (GH) GH release is regulated by Growth hormone–releasing hormone (GHRH) Growth hormone–inhibiting hormone (GHIH) (somatostatin)

61 + - GH + Growth Hormone Actions: Somatostatin GHRH IGF-1 Growth
Insulin Antagonism Growth Insulin Antagonism Growth Lipolysis

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

63 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 Thyroid Stimulating Hormone (TSH)

65 Thyroid-Stimulating Hormone (Thyrotropin)
Produced by thyrotrophs of the anterior pituitary Stimulates the normal development and secretory activity of the thyroid

66 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 Hypothalamus TRH Anterior pituitary TSH Thyroid gland Thyroid hormones
Stimulates Target cells Inhibits Figure 16.7

68 Adrenocorticotrophic Hormone (ACTH)

69 Adrenocorticotropic Hormone (Corticotropin)
Secreted by corticotrophs of the anterior pituitary Stimulates the adrenal cortex to release corticosteroids

70 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 Gonadotropins (FSH, LH)

72 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 Regulation of gonadotropin release
Gonadotropins Regulation of gonadotropin release Triggered by the gonadotropin-releasing hormone (GnRH) during and after puberty Suppressed by gonadal hormones (feedback)

74 Prolactin (PRL)

75 Prolactin (PRL) Secreted by lactotrophs of the anterior pituitary Stimulates milk production

76 Regulation of PRL release
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 Posterior Pituitary (neurohypophosis)

78 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 Oxytocin

80 Oxytocin Stimulates uterine contractions during childbirth by mobilizing Ca2+ through a PIP2-Ca2+ 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 Antidiuretic Hormone (ADH)

82 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 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 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 Thyroid Gland Hormones

86 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 Figure 16.8

88 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 Major metabolic hormone
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 Actually two related compounds
Thyroid Hormone (TH) Actually two related compounds T4 (thyroxine); has 2 tyrosine molecules + 4 bound iodine atoms T3 (triiodothyronine); has 2 tyrosines + 3 bound iodine atoms Majority of circulating hormone is T % T % T3 for thyroid hormone to be built, it requires iodine

91 Transport and Regulation of TH
T4 and T3 are transported by thyroxine-binding globulins (TBGs) Both bind to target receptors, but T3 is ten times more active than T4 Peripheral tissues convert T4 to T3 T3 is more metabolically active than T4

92 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 Hypothalamus TRH Anterior pituitary TSH Thyroid gland Thyroid hormones
Stimulates Target cells Inhibits Figure 16.7

94 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 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 Figure 16.10

97 Calcitonin Produced by parafollicular (C) cells Antagonist to parathyroid hormone (PTH) Inhibits osteoclast activity and release of Ca2+ from bone matrix Ca2+ goes from blood to bone; lowers Ca2+ levels in the blood No important role in humans; removal of thyroid (and its C cells) does not affect Ca2+ homeostasis

98 Parathyroid Gland Hormones

99 chief cells secrete parathyroid hormone (PTH)
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 Ca2+ homeostasis Ca2+ moves from bone to blood; increases blood levels of Ca2+

100 Pharynx (posterior aspect) Chief cells (secrete parathyroid hormone)
gland Parathyroid glands Oxyphil cells Esophagus Trachea Capillary (a) (b) Figure 16.11

101 Parathyroid Hormone Functions
Stimulates osteoclasts to digest bone matrix Enhances reabsorption of Ca2+ and secretion of phosphate by the kidneys Promotes activation of vitamin D (by the kidneys); increases absorption of Ca2+ by intestinal mucosa Negative feedback control: rising Ca2+ in the blood inhibits PTH release

102 Parathyroid Hormone

103 1 2 3 Hypocalcemia (low blood Ca2+) stimulates
parathyroid glands to release PTH. Rising Ca2+ in blood inhibits PTH release. Bone PTH activates osteoclasts: Ca2+ and PO43S released into blood. 1 2 PTH increases Ca2+ reabsorption in kidney tubules. Kidney PTH promotes kidney’s activation of vitamin D, which increases Ca2+ absorption from food. 3 Intestine Ca2+ ions Bloodstream PTH Molecules Figure 16.12

104 Homeostatic Imbalances of PTH
Hyperparathyroidism due to tumor Bones soften and deform Elevated Ca2+ 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 Adrenal Gland Hormones

106 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 Three layers and the corticosteroids produced
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 Zona glomerulosa Zona fasciculata Zona reticularis Adrenal medulla
Capsule Zona glomerulosa Zona fasciculata Adrenal gland Cortex • Medulla • Cortex Zona reticularis Kidney Medulla Adrenal medulla (a) Drawing of the histology of the adrenal cortex and a portion of the adrenal medulla Figure 16.13a

109 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 Hormones of the Adrenal Cortex

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

112 water; increased K+ excretion
Primary regulators Other factors Blood volume and/or blood pressure K+ in blood Stress Blood pressure and/or blood volume Hypo- thalamus Heart Kidney CRH Direct stimulating effect Anterior pituitary Renin Initiates cascade that produces ACTH Atrial natriuretic peptide (ANP) Angiotensin II Inhibitory effect 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 Figure 16.14

113 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 Glucocorticoids (Cortisol): Zona Fasiculata
Keep blood sugar levels relatively constant Maintain blood pressure by increasing the action of vasoconstrictors

115 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 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 Hormones of the Adrenal Cortex

118 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 Figure 16.15

120 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 Glucose and sodium in blood are low
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 Gonadocorticoids

123 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 DHEA and Androgen production

125 Chromaffin cells secrete epinephrine (80%) and norepinephrine (20%)
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 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 Figure 16.16 Short-term stress More prolonged stress Stress
Nerve impulses Hypothalamus CRH (corticotropin- releasing hormone) Spinal cord Corticotroph cells of anterior pituitary Preganglionic sympathetic fibers To target in blood Adrenal cortex (secretes steroid hormones) Adrenal medulla (secretes amino acid- based hormones) ACTH Catecholamines (epinephrine and norepinephrine) Mineralocorticoids Glucocorticoids Short-term stress response Long-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 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 Figure 16.16

128 Major Events in the General Stress Response

129 Pancreas Hormones

130 Pancreas

131 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 Pancreatic islet (of Langerhans) • (Glucagon- producing) cells
• (Insulin- producing) cells Pancreatic acinar cells (exocrine) Figure 16.17

133 Major target is the liver, where it promotes
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 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 Stimulates glucose uptake by cells
Insulin Tissue cells Stimulates glycogen formation Pancreas Glucose Glycogen Blood glucose falls to normal range. Liver Stimulus Blood glucose level Stimulus Blood glucose level Blood glucose rises to normal range. Pancreas Liver Glucose Glycogen Stimulates glycogen breakdown Glucagon Figure 16.18

136 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 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 Table 16.4

139 Gonadal Hormones

140 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 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 Other Hormone Producing Tissues

143 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 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 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 Developmental Aspects

147 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 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 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


151 directly onto their target cell into the cerebrospinal fluid
A major difference between neurotransmitters and hormones is that hormones are secreted ____________. directly onto their target cell into the cerebrospinal fluid into ducts into the blood Answer: d. into the blood

152 A major determinant of a hormone’s mechanism of action is __________.
whether the hormonal molecule is hydrophobic or hydrophilic its size whether it is rapid acting or slow acting if it activates gene activity or not Answer: a. whether the hormonal molecule is hydrophobic or hydrophilic

153 Receptors for steroid hormones are commonly located _________.
inside the target cell on the plasma membrane of the target cell in the blood plasma in the extracellular fluid Answer: a. inside the target cell

154 direct gene activation a second messenger endocytosis
Interaction with a membrane-bound receptor will transmit the hormonal message via __________. depolarization direct gene activation a second messenger endocytosis Answer: c. a second messenger

155 Which of the following molecules act as second messengers?
cAMP Ca2+ Na+ A and B Answer: d. All of the above

156 the steroid hormone may direct the synthesis of the protein.
It’s possible for a steroid hormone and a protein hormone to affect the same intracellular protein because: the steroid hormone may direct the synthesis of the protein. the protein hormone may activate the protein. the protein hormone may direct the synthesis of the protein. of all of the above. Answer: d. all of the above

157 In order for a hormone to activate a target cell, the target cell must possess _______.
a receptor a second messenger the hormone a chaperone Answer: a. a receptor

158 The most common form of endocrine malfunction is __________.
failure of the gland to produce the hormone insensitivity of the target cell to the hormone overproduction of the hormone by the gland All of the above are common disorders. Answer: d. All of the above are common disorders.

159 When the pancreas releases insulin in direct response to blood glucose, this is an example of ________ stimulation. humoral neural hormonal negative feedback Answer: a. humoral

160 When two people kiss, their neurohypophyses releases oxytocin
When two people kiss, their neurohypophyses releases oxytocin. This is an example of __________ stimulation. humoral neural hormonal negative feedback Answer: b. neural

161 When the ovaries secrete estrogen in response to the hormone GnRH, this is an example of __________ stimulation. humoral neural hormonal negative feedback Answer: c. hormonal

162 Blood levels of hormone are kept within very narrow ranges by _________ mechanisms.
humoral neural hormonal negative feedback Answer: d. negative feedback

163 Hormones secreted into the hypophyseal portal system are delivered directly to the ________.
neurohypophysis adenohypophysis median eminence infundibulum Answer: b. adenohypophysis

164 hyposecretion of oxytocin hypersecretion of oxytocin
A patient is displaying high volumes of urine output and severe dehydration. The most likely cause is _________. hyposecretion of oxytocin hypersecretion of oxytocin hyposecretion of ADH hypersecretion of ADH Answer: c. hyposecretion of ADH

165 Common secretion(s) of the thyroid gland is (are) _________.
calcitonin Triiodothyronine (T3) Thyroxine (T4) all of the above Answer: d. all of the above

166 hypersecretion of calcitonin
A patient is losing weight rapidly, sweating profusely, and is always anxious. The patient may be suffering from _______. hypothyroidism cretinism hyperthyroidism hypersecretion of calcitonin Answer: c. hyperthyroidism

167 Thyroid hormones; calmodulin Calcitonin; PTH
Two hormones govern calcium regulation. ________ acts to elevate blood calcium levels, whereas ________ lowers blood calcium levels. PTH; calcitonin Thyroid hormones; calmodulin Calcitonin; PTH Calcitonin; thyroid hormone Answer: a. PTH; calcitonin

168 __________ is the adrenal hormone responsible for maintaining appropriate blood sodium levels.
Cortisol DHEA Aldosterone Epinephrine Answer: c. Aldosterone

169 _________ trigger(s) secretion of aldosterone.
Increased K+ Angiotensin II ANP Both a and b Answer: d. Both a and b

170 During times of stress, elevated levels of _______ often occur, which explains why we get a cold during final exam time. cortisol aldosterone ACTH androgens Answer: a. cortisol

171 Along with the sympathetic nervous system, the _________ is the other primary mediator of acute stress. adrenal medulla adrenal cortex zona glomerulosa zona reticularis Answer: a. adrenal medulla

172 The secretion of ________ helps regulate our circadian rhythms.
estrogen testosterone thyroid hormones melatonin Answer: d. melatonin

173 The thymus secretes the hormone(s) ______________.
thymopoietin thymosin thymic factor all of the above Answer: d. all of the above

174 Which of the following structures produces a hormone responsible for stimulating red blood cell production? Stomach Heart Kidney Skin Answer: c. Kidney

175 Which of the following structures produces a precursor to hormonal vitamin D, important for Ca2+ regulation? Stomach Heart Kidney Skin Answer: d. Skin

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