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Anatomy & Physiology Chapter 16 Endocrine System.

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Presentation on theme: "Anatomy & Physiology Chapter 16 Endocrine System."— Presentation transcript:

1 Anatomy & Physiology Chapter 16 Endocrine System


3 Endocrine vs. Nervous System  See Table 16-1

4 Classification of hormones by chemical structure

5 Steroid hormones  Derived from cholesterol  Lipid-soluble  Pass through plasma membranes easily

6 Nonsteroid hormones  Synthesized primarily from amino acids  Protein hormones: long chains of amino acids ex: insulin, PTH  Glycoproteins: protein hormones with a carbohydrate group attached ex: FSH, LH  Peptide hormones: short chain of amino acids ex: oxytocin, ADH  Amino acid derivatives: derived from a single amino acid Amine hormones: derived from tyrosine ex:epinephrine Iodine added to tyrosine ex: thyroid hormones

7 General Principles of Hormone Action  Bind to a specific receptor on cell by “lock- and-key” mechanism  Some hormones are attached to plasma proteins in bloodstream  Since blood carries hormones most everywhere lots more produced than makes it to its target

8 Mechanism of steroid hormone action (Mobile-receptor hypothesis)  Attach to soluble plasma proteins in blood  Receptors usually found within the cell  Regulate cells by regulating production of certain critical proteins  Amount of steroid hormone present determines magnitude of target cell’s response  Response to steroid hormones often slow

9 Mechanisms of Nonsteroid Hormones  Second messenger mechanism: also called fixed-membrane-receptor hypothesis  Nuclear receptor mechanism

10 Second messenger mechanism  Binds to receptors on target cell’s plasma membrane  Then second messenger within cell triggers appropriate cellular changes  Most use cAMP as second messenger  Operates more quickly than steroid mechanism

11 Nuclear receptor mechanism  Small iodinated amino acids (T3 & T4)  Enter target cell & bind to receptors associated with DNA which triggers transcription of mRNA

12 Regulation of hormone secretion  Usually part of a negative feedback loop and is called endocrine reflexes  Endocrine cells often sensitive to changes produced by its target cells  May be regulated by hormone produced by another gland, esp pituitary gland  May be influenced by nervous system input

13 Prostaglandins  Lipid molecules  Tissue hormones: secretion produced in tissues & diffuse short distance only to other cells in same tissue  Tissues known to secrete prostaglandins: kidneys, lungs, iris, brain, thymus

14 Vocabulary Words  Hormone  Synergism  Permissiveness  Antagonism  Tropic hormones  Sex hormones  Anabolic hormones

15 Pituitary Gland

16 Pituitary gland (Hypophysis)  Lies within sella turcica of skull  Connected to the hypothalamus by a stalk, infundibulum  Consists of 2 different glands Adenohypohysis or anterior pituitary Neurohypophysis or posterior pituitary

17 Anterior Pituitary  Two parts pars anterior: major part pars intermedia  5 types of secretions Somatrophs-secrete GH Corticotrophs-secrete ACTH Thyrotrophs: secrete TSH Lactotrophs: secrete prolactin Gondatrophs: secrete LH and FSH

18 Growth Hormone (GH)  Promotes protein anabolism thus promotes growth of bones, muscles  Promotes lipid mobilization & catabolism  Indirectly inhibits glucose metabolism  Indirectly increases blood glucose levels

19 Prolactin (PRL)  During pregnancy promotes breast development  After birth stimulates mammary gland to begin milk secretion

20 Tropic hormones  Have stimulating effect on other endocrine glands  Thyroid stimulating hormone: TSH  Adrenocorticotropic hormone: ACTH  Follicle stimulating hormone: FSH  Luteinizing hormone: LH

21 TSH  Maintains growth & development of thyroid gland & causes it to secrete its hormones

22 ACTH  Promotes & maintains normal growth of cortex of adrenal gland & stimulates it to secrete some of its hormones

23 Gonadotropins  Stimulate growth & development of gonads  FSH: stimulates follicles (with ovum) to maturity, also stimulates follicle to secrete estrogen; in male: stimulates development of seminiferous tubules  LH: stimulates formation of corpus luteum; in males: stimulates interstitial cells in testes to develop & secrete testosterone

24 Control of secretion of anterior pituitary  Hypophyseal portal system: complex of small blood vessels between hypothalamus & anterior pituitary  Hypothalamus secretes releasing hormones through this system  During times of stress cerebral cortex can send impulses to hypothalamus to secrete releasing hormones thus mind- body link

25 Posterior pituitary  Storage & release site for: ADH (antidiuretic hormone) Oxytocin  Hormones are not made within the pituitary but within the supraoptic or paraventricular nuclei of hypothalamus  Release of these hormones thus controlled by nervous stimulation

26 Antidiuretic hormone  Prevents formation of a large volume of urine  Release triggered by osmoreceptors near supraoptic nucleus

27 Oxytocin  Stimulates contraction of uterine muslces  Causes ejection of milk from breasts  Regulated by a positive feedback mechanism


29 Pineal gland  Located on dorsal surface of brain’s diencephalon  Member of both nervous system & endocrine system  Produces melatonin, functions to support biological clock

30 Thyroid gland  In neck, on anterior & lateral surface of trachea just below the larynx  Composed of structural units called follicles  Hormones: Thyroid hormones Calcitonin

31 Thyroid hormones  T3: principal thyroid hormone  T4: most abundant, precursor of T3  Thyroid gland stores thyroid hormone as thyroglobulins  Regulate metabolic rate of all cells

32 Calcitonin  Produced by parafollicular cells of thyroid  Influences processing of calcium by bone cells by decreasing blood calcium levels  Antagonist to parathyroid hormone

33 Parathyroid gland  4-5 of them embedded on posterior surface of thryoid’s lateral lobes  Hormone: PTH (parathryroid hormone)

34 PTH  Antagonist to calcitonin  Acts on bones & kidneys to increase blood calcium  Bones: calcium & phosphate released from bones  Kidneys: calcium reabsorbed, phosphate secreted, activates Vitamin D in kidney which permits Ca to be absorbed in intestine

35 Adrenal glands  On top of kidneys  Adrenal cortex: outer part Zona glomerulosa: mineralocorticoids Zona fasiculata: glucocorticoids Zona reticularis: gonadocorticoids  Adrenal medulla: inner portion

36 Mineralocorticoids  Aldosterone: important mineralocorticoid  Primary function is maintenance of sodium homeostasis by increasing sodium reabsorption in kidneys  Increase water retention & promotes loss of potassium  Secretion controlled by renin-angiotensin & blood potassium concentration

37 Glucocorticoids  Cortisol most significant  Affect every cell in body  Protein mobilizing, lipid catabolism as energy source, secretion increase in times of stress, essential for maintaining normal blood pressure, decrease in number of WBCs

38 Gonadocorticoids  Secretes small amounts of male hormones  Released from zona fasiculata & zona glomerulosa  Influences appearance of pubic & axillary hair

39 Adrenal medulla  Composed of neurosecretory tissue  Produce epinephrine & norepinephrine  Prolong & enhance effects of sympathetic stimulation (fight or flight response)

40 Pancreas  Endocrine portion: pancreatic islets (or islets of Langerhans)  Alpha cells: secrete glucagon  Beta cells: secrete insulin  Delta cells: secrete somatostatin  Pancreatic polypeptide cells: secrete pancreatic polypeptide

41 Glucagon  Increase blood glucose levels by stimulating conversion of glycogen to glucose in liver cells  Also stimulates gluconeogenesis in liver  Hyperglycemic effect

42 Insulin  Promotes movement of glucose, amino acids, fatty acids into tissue cells  Lowers blood glucose

43 Somatostatin  Regulates other endocrine cells of pancreatic islets by inhibiting secretion

44 Gonads  Primary sex organs Males: testes Females: ovaries

45 Testes  Interstitial cells within testes produce testosterone  Responsible for growth & maintenance of male sexual characteristics & for sperm production

46 Ovaries  Estrogens: secreted by follicles, promote development & maintenance of female sexual characteristics, breast development, menstrual cycle  Progesterone: secreted by corpus luteum, maintains lining of uterus necessary for pregnancy

47 Placenta  Produces human chorionic gonadotropin (hCG), serves as a signal to maintain uterine lining for pregnancy  Temporary endocrine gland

48 Thymus  Atrophies at puberty  Produces thymosin & thymopoietin  Stimulate production of T cells

49 Gastric & Intestinal Mucosa  Secretin: reduce acid secretion, triggers pancreas to produce bicarbonate  CCK: trigger pancreas to release digestive enzymes, gall bladder contraction  Ghrelin: stimulates hypothalamus to boost appetite

50 Heart  Atrial natriuretic hormone (ANH): promotes loss of sodium in urine thus it opposes increase in blood volume or blood pressure  Antagonistic to ADH & aldosterone

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