Flashcards in Physiology - Exam 2, Deck #2 - Endocrine Deck (126):
What two systems are responsible for controlling bodily functions?
1. Nervous System- controls rapid activities of the body = muscular contractions, rapidly changing visceral events, rates of secretion of some endocrine glands;
2. Endocrine System – Principally regulates the metabolic functions of the body
What is controlled by the ENDOCRINE system?
-Metabolic functions of the body;
-Rates of chemical reactions in cells;
-Transport of substances across cell membranes;
-Other parts of cell metabolism — growth and secretion
What is a Hormone?
-A chemical substance that is secreted into body fluids by one cell or a group of cells that exert a physiological control effect on other cells of the body
What are Target Cells/Tissues/Organs?
Those cells, tissues, or organs which are controlled by a specific hormone
What are the types of Hormones?
2. Polypeptides and proteins
What are Amine Steroids?
-Derived from the amino acids tyrosine and tryptophan: epinephrine, thyroxine;
-Hormones secreted by the arena medulla, thyroid, and pineal gland;
What are Polypeptides and Protein Hormones?
1. Polypeptides = generally contain < 100 amino acids
-EX: antidiuretic hormone;
2. Protein = > 100 amino acids:
EX: growth hormone
What are Glycoprotein Hormones?
-Consist of a protein bound to one or more carbohydrate groups:
EX: FSH, LH — Gonadotrophic hormones
What are Steroid Hormones?
-Derived from cholesterol:
EX: testosterone, estradiol, progesterone, and cortisol.
What are the 2 mechanisms by which hormones function?
1. Hydrophilic hormones – use a second messenger system that activates existing
- Adenylate cyclase- cAMP system
- Phospholipase C-Ca++ system
- Tyrosine Kinase system
2. Hydrophobic hormones – use nuclear receptor proteins that activate genes
- Steroid Hormones
- Thyroxine and triiodothyronine
What hormones use the Second Messenger System?
-Glycoprotein and polypeptide;
What are the 3 systems of Second Messengers?
1. Adenylate cyclase- cAMP system
2. Phospholipase C-Ca++ system
3. Tyrosine Kinase system
What is cAMP?
-Intracellular hormonal mediator for POLYPEPTIDE & GLYCOPROTEIN HORMONES;
-Second messenger for hormone action;
-Must be rapidly INACTIVATED to function as a second messenger effectiely
What is the mechanism of cAMP?
1. Hormone binds to receptor causing dissociation of a G-protein subunit;
2. G-protein subunit binds to & activates ADENYLATE CYCLASE;
3. Which converts ATP into cAMP;
4. cAMP attaches to inhibitory subunit of protein kinase
5. Inhibitory subunit dissociates, ACTIVATING protein kinase;
6. Which PHOSPHORYLATES enzymes that produce hormone’s effects
What is Phosphodiesterase?
-An enzyme within the target cell that hydrolyzes cAMO into inactive fragments;
-This inactivation means that the stimulatory effect of cAMP as a second messenger depends upon the CONTINUOUS generation of new cAMP and thus dependent upon the level hormone secretion
What is cGMP?
-Cyclic Guanosine Monophosphate (cGMP);
-Functions as a second messenger in some cases;
-EX: regulatory molecule of nitric oxide effects smooth muscles by stimulating production of cGMP in target cells
When do cAMP and cGMP interact?
-Effects may be either antagonistic or complementary;
-EX: control of cell division and cell cycle is related to the ratio of cAMP to cGMP
How is the concentration of Ca2+ maintained?
-Due to active transport pumps in the plasma and ER membranes of some cells
What is Ca2+ used for in cells?
1. Entry of Ca2+ through voltage-gated Ca2+ channels in terminal boutons of axons = Release of neurotransmitters;
2. Excitation-contraction coupling for electrical stimulation of muscles by release of Ca2+ from the sarcoplasmic reticulum;
3. Second-messenger system for hormones — Phospholipase-C-Ca2+
What is the Phospholipase-C-Ca2+ system?
-Serves as 2nd messenger system for some hormones (hydrophilic);
-Hormone binds to surface receptor, activates G-protein, which activates phospholipase C
What is the mechanism of the P-C-Ca2+ second messenger?
1. Phospholipase C splits a membrane phospholipid into 2nd messengers IP3 (inositol triphosphate) & DAG (diacylglycerol);
3. IP3 diffuses through cytoplasm to ER where it binds to receptor proteins — causing Ca2+ channels to open;
4. ER accumulates Ca2+ ay active transport, there is a steep gradient favoring DIFFUSION of Ca2+ into the cytoplasm;
5. Ca2+ diffuses into cytoplasm & binds to & activates CALMODULIN;;
6. Ca2+-Calmodulin activates PROTEIN KINASES which phosphorylate enzymes that produce hormone's effects
What 2 second messengers can Epinephrine use to act?
1. Beta-adrenergic effect with cAMP;
2. Alpa-adrenergic effect with Ca2+
What does Insulin promote?
ANABOLIC Hormone — acts like other regulatory molecules called Growth Factors;
-Promotes glucose and amino acid transport;
-Synthesis of glycogen, fat and protein;
Targets = Liver, muscle, adipose
What is Tyrosine Kinase?
The receptor protein located in the plasma membrane for insulin and growth factors
What is the Tyrosine Kinase Second Messenger System?
-Used by insulin & many growth factors to cause cellular effects;
-Surface receptor is tyrosine kinase;
-Consists of 2 units that form active dimer when insulin binds
What are the actions of Tyrosine Kinase?
1. Adds PO4- to tyrosine (AA) within proteins;
2. Has 2 units that dimerize when they bind Insulin (ligand) to form active Tyrosine Kinase enzyme;
3. Activated tyrosine kinase phosphorylates SIGNALING MOLECULES that induce hormone/growth factor effects
What are Signaling Molecules?
Some inase enzymes that phosphorylate and activate other second-messenger systems
How does Insulin indirectly stimulate diffusion of glucose into the muscle, liver and adipose?
-Indirectly stimulates the insertion of GLUT-4 carrier proteins = facilitated diffusion of glucose;
- Binding insulin to the receptor causes the activation of GLYCOGEN SYNTHETASE = enzymes in liver and muscle that catalyzes the production of glycogen in these target organs
What types of hormones bind to nuclear receptors and cause the activation of genes cells AFTER being transported to the gene with a carrier protein?
-LIPOPHILIC Hormones — activate genes;
1. Steroid Hormones of the adrenal cortex, ovaries, and testes;
2. Thyroxine (tetraiodothyronine)
How do Lipid hormones enter target cells?
-Lipid hormones travel in blood attached to CARRIER PROTEINS;
-They dissociate from carriers to diffuse thru plasma membrane of target;
-Receptors are called NUCLEAR HORMONE RECEPTORS
What are Nuclear Hormone Receptors?
-Serve as TRANSCRIPTION FACTORS when bound to hormone ligands = Activate transcription;
-Constitute a "superfamily" composed of steroid family & thyroid hormone family (which includes vitamin D & retinoic acid)
Where can steroid hormones be secreted from?
1. Corpus luteum of the ovaries;
2. Adrenal cortex;
3. Leydig cells of testes;
4. Follicles of ovaries
What is the mechanism of action for Aldosterone (lipid soluble)?
1. ALD is lipid-soluble and easily diffuses through plamsa membrane;
2. In cell, binds to ALD receptor in the cytoplasm;
3. ALD-Receptor complex enter nucleus and binds DNA;
4. Binding to DNA stimulates the synthesis of mRNA to code for proteins;
5. mRNA leaves nucleus, through cytoplasm, and binds ribosomes where it directs protein synthesis;
6. Proteins made on ribosomes produce the response of the cell to ALD
What are the 2 major Thyroid hormones?
1. Thyroxine (T4);
2. Triiodothyronine (T3)
What is the mechanism of Thyroid hormone action?
-Thyroid secretes 90% T4 (thyroxine) & 10% T3;
-99.96% of T4 in blood is bound to carrier protein = THYROID BINDING GLOBULIN - TBG;
-Only FREE can enter cells, so bound is reservoir;
-T4 converted to T3 inside cell;
-T3 binds to receptor protein located in cytoplasm and the complex moves to the nucleus
-T3 & receptor bind to 1 half-site ;
-Other half-site binds RETINOIC ACID;
-Two partners form HETERODIMER that activates HRE;
-Stimulates transcription of target gene
What are the important Endocrine GLANDS?
-Pituitary or hypophysis
-Gastrointestinal tract cells
What are ENDOCRINE Glands?
-Are ductless & secrete hormones into bloodstream;
-Hormones go to target cells that contain receptor proteins;
-NEUROHORMONES are secreted into blood by specialized neurons ;
-Hormones affect METABOLISM of targets
What is the Pituitary Gland?
"Master gland" – hormones mainly influence other ENDOCRINE glands physiology and secretion = Troponins;
-Known as the HYPOPHYSIS;
-About the size of the tip of the little finger;
-Lies in a small bony cavity at the base of the brain;
-Behind the optic chiasma in the midbrain;
-Reddish-gray oval structure
What are Troponins?
Pituitary hormones that influence other endocrine glands;
-Carried by the blood to other target glands where they aid in the maintenance of glands as well as stimulating them to produce their own hormones or hormones
What 2 sources form the Pituitary?
1. Neural source – downgrowth of the floor of the thalamus called the infundibulum = NEUROHYPOPHYSIS OR THE POSTERIOR LOBE
2. Ectoderm of the primitive oral cavity = anterior and intermediate lobe (fetus only) = adenohypophysis and pars intermedia
What is the Hypothalamic-Hypophyseal Portal System?
- Supplies the ANTERIOR & INTERMEDIATE pituitary because blood supply is INDEPENDENT of that of the brain proper;
-The hypophysial arteries branched from the internal carotid artery;
-The system supplies releasing and inhibiting factors to the anterior pituitary — very little nerve supply in the anterior pituitary
What are Releasing Factors?
-Released from cells of the hypothalamus and travel in the hypothalamic-hypophyseal portal system to control release of hormones from the ADENOHYPOPHYSIS (anterior lobe)
What hormone is secreted by the Pars Intermedia (Intermediate Lobe)?
-Secrete only 1 hormone;
-Melanocyte stimulating hormone (MSH);
-MSH acts in the dispersion of pigment granules which are import ant in the darkening of skin;
-insignificant amounts in man
How is the Pituitary Gland situated at the base of the brain?
-Structurally & functionally divided into ANTERIOR & POSTERIOR lobes;
-Hangs below hypothalamus by INFUNDIBULUM — connection segment than allows it to hang under the hypothalamus;
1. Anterior = Adenopophysis;
2. Posterior = Neuroppophysis
What is the difference the hormones form the Anterior and Posterior Lobes?
1. Anterior produces own hormones — CONTROLLED by hypothalamus;
2. Posterior stores & releases hormones — MADE in hypothalamus
What hormones are released by the POSTERIOR Pituitary Gland?
-Releases two neurohormones which are produced in the hypothalamus and released from axonal ends in the posterior lobe
1. Vasopressin — antidiuretic hormone (ADH);
What is Vasopressin?
From the SUPRAOPTIC NUCLEUS;
-Promotes the reabsorption of water from the collecting ducts by inserting aquaporin channels in the CD;
- High doses – vasoconstriction of vascular beds — elevates blood pressure
What is Oxytocin?
From the PARAVENTRICULAR NUCLEUS;
-Females — stimulates uterine contractions during labor (childbirth)
-Females — postpartum – stimulates contractions of the mammary gland alveoli and ducts which results in the milk ejection reflex in lactating women;
-Males — rise in secretion at the time of ejaculation
What controls the release of the hormones from the Posterior Pituitary?
-Release is controlled by NEUROENDOCRINE REFLEXES
-Release stimulated by osmoreceptor neurons in hypothalamus;
-Inhibited release by stretch receptors in left atrium
2. Oxytocin — Released by suckling reflex
What is the Anterior Pituitary Gland?
-Secretes 6 trophic hormones that maintain size of targets;’-High blood levels cause target to HYPERTROPHY;
-Low levels cause ATROPHY
What hormones are released by the ANTERIOR Pituitary Gland?
Releases 6 tropic hormones;
1. Growth hormone — Somatotropin (STH);
2. Prolactin (lactogenic hormone);
3. Follicle Stimulating Hormone (FSH);
4. Luteinizing Hormone (LH);
5. Thyrotopic Hormone — Thydoid stimulating hormone (TSH);
6. Adrenocortico homrone (ACTH)
What is Growth Hormone — Somatotropin?
Stimulates growth of long bones at the epiphyses and of soft tissue;
-Anabolic effects on nitrogen, carb, and fat metabolism;
-Elevates glycogen stores
What happens to growth when Pituitary is removed?
-Removing the pituitary in young animals = STOP growing;
-Replacement of growth hormone with purified preparations will restore growth
What is Prolactin?
Stimulates the growth of the mammary glands during pregnancy and the secretion of milk into the alveoli of the breasts
What is Follicle Stimulating Hormone?
Stimulates the maturation of the ovarian (Graffian) follicle prior to ovulation;
-Also the production of estrogen in the female;
-Stimulates spermiogenesis in the males
What is Luteinizing Hormone?
Causes ovulation and development of the corpus luteum and liberation of estrogen and progesterone in the female;
-Stimulates testosterone production in the males
What is Thyrotrophic Hormone (TSH)?
Functions to maintain the thyroid gland and stimulates it to produce the hormones thyroxine and triiodothyronine;
-TOO MUCH — too much Thyroxine — hyperthyroidism = Graves disease;
-TOO LITTLE — too little Thyroxine — hypothyroidism
What is Adrenocorticotropic Hormone (ACTH)?
1. Stimulates the secretion of the adrenal cortical hormones by the adrenal cortex;
2. Increases excretion of nitrogen, potassium, and phosphorous in the kidney;
3. Increases retention of sodium and chloride in the kidney;
4. Increases blood glucose level and increases the excretion of uric acid
What controls the release of Anterior Pituitary hormones?
-Release of anterior pituitary hormones is controlled by HYPOTHALAMIC RELEASING & INHIBITING FACTORS & by feedback from levels of target gland hormones
How do Releasing and Inhibiting factors act on the Anterior Pituitary?
-Releasing & inhibiting hormones from hypothalamus are released from axon endings into capillary bed in MEDIAN EMINENCE;
-Carried by hypothalamo-hypophyseal portal system directly to another capillary bed in A. Pit. ;
-Diffuse into A. Pit. & regulate secretion of its hormones
What is Feedback Control of the Anterior Pituitary?
-Involves short FEEDBACK LOOP in which retrograde flow of blood & hormones from A. Pit. to hypothalamus INHIBITS secretion of releasing hormone;
-Involves negative feedback of target gland hormones;
-& during menstrual cycle, estrogen stimulates “LH surge” by positive feedback
What are the Releasing Factors?
1. Corticotropin-RH (CRH) — Stimulates ACTH;
2. Gonadotropic-RH (GRH) — Stimulates FSH and LH;
2. Prolactin-inhibitng hormone (PIH) — Inhibits prolactin secretion;
4. Somatostatin — Inhibits growth hormone;
5. Growth hormone-RH (GHRH) — Stimulates growth hormone secretion
How does the higher brain affect the Anterior Pituitary?
Hypothalamus receives input from higher brain centers that can affect anterior pituitary secretion;
E.X. psychological stress affects circadian rhythms, menstrual cycle, & adrenal hormones
What is the Pineal Gland?
-Located in basal forebrain near thalamus;
-Secretes MELATONIN in response to activity of suprachiasmatic nucleus (SCN) of hypothalamus
What is the suprachiasmatic nucleus (SCN)?
-SCN is primary timing center for circadian rhythms;
-Reset by daily light/dark changes;
-MELATONIN is involved in aligning physiology with sleep/wake cycle & seasons;
-Secreted at night & is inhibited by light;
-Inhibits GnRH (antigonadotropic) in many animals
What is the Thyroid Gland?
-Yellow/reddish lobulated, shield-shaped gland;
-Located in the neck near the junction of the larynx and trachea;
-Size and shape fluctuate with stage of development;
-Blood supply is very rich, probably more blood flow per wt. than anywhere in the body;
-Secretes T4 & T3 which set BMR & are needed for growth, development
What is the Alveolus or Follicle of the Thyroid Gland?
-Structural unit of the Thyroid Gland;
-Filled with COLLOID – store for thyroxine (T4) or triiodothyronine (T3)
in combination with thyroglobulin;
-Primary calorigenic action
What is the Calorigenic action of the Thyroid Gland?
-Primary action is on metabolic rate — Calorigenic;
-Hormones directly increase the rate of oxidation of biochemical subs. in the cells;
-Thyroxine is essential for growth/development;
--In vertebrates, can’t reach adult form without thyroid hormones
What are the functions of T4 and T3?
1. Increase rate of absorption of sugar into cells and deletion of liver glycogen;
2. Essential for bone development;
3. Necessary for carotene to Vit. A;
4. Necessary for water and mineral metabolism;
5. Necessary for nervous, muscular, and circulatory system;
**Release controlled by the circulating level of TSH
How are Thyroid hormones produced?
-Iodide (I-) in blood is actively transported into follicles & secreted into colloid;
-Where it is oxidized to iodine (I2) & attached to tyrosines of THYROGLOBULIN =
-A large storage molecule for T4 & T3 ;
-TSH stimulates hydrolysis (breaking off) of T4 & T3s from thyroglobulin & then secretion
What are the abnormalities of the Thyroid Gland?
-Hyperthyroidism = too much
-Hypothyroidism = too little
-goiter = inflammation of the thyroid
What is Goiter?
-Without enough dietary iodide, T4 & T3 cannot be made & levels are low;
-Low T4 & T3 don’t provide negative feedback & TSH levels go up;
-Because TSH is a trophic hormone, thyroid gland grows and swells;
-Resulting in a GOITER
What disease results from Hyperthyroidism?
-Goiters are also produced by GRAVE'S DISEASE;
-Autoimmune disease where antibodies act like TSH & stimulate thyroid gland to grow & oversecrete = hyperthyroidism;
-Characterized by EXOPTHALMOS, weight loss, heat intolerance, irritability, high BMR
What is Hypothyroidism?
-People with inadequate T4 & T3 levels are hypothyroid;
-Have low BMR, weight gain, lethargy, cold intolerance;
-& MYXEDEMA = puffy face, hands, feet;
-During fetal development hypothyroidism can cause CRETENISM = severe mental retardation
What is Calcitonin?
-Hormone that LOWERS blood calcium levels;
-Secreted by the Parafollicular = C cells in Thyroid Gland;
-Physiological significance of calcitonin in adults is not understood
What is the mechanism of action of Calcitonin?
-It works in concert with parathyroid hormone and Vitamin D3 to regulate the calcium level of the blood ;
-Lowers blood calcium level by inhibiting the dissolution (breakdown) of calcium phosphate crystals of bone by INHIBITING the activity of OSTEOCLASTS ;
-Lowers blood calcium level by inhibiting the reabsorption of calcium and phosphate in the nephrons
What are the Parathyroid Glands?
-Yellow-brown ovoid bodies (4) connected to the posterior surface of the thyroid gland; 0.05-3.0gm;
-Secrete parathyroid hormone = parathormone = PTH
What is the primary function of Parathormone?
*Most important hormone for blood Ca2+ levels
-Proper maintenance of the calcium-phosphorous ratio in the blood and tissues;
-Parathormone influences calcium metabolism in three ways:
1. Increases Ca2+ absorption from the intestinal tract;
2. Increases Ca2+ mobilization from bone (increased breakdown);
3. Increases Ca2+ reabsorption from the kidneys
What stimulates the Parathormone?
-Release stimulated by decreased blood Ca2+;
-Acts on bones, kidney, & intestines to increase blood Ca2+ levels
What is the Thymus Gland?
-Two elongated, flask shaped lobes which occupy a region above the heart and between the lungs — around trachea, below thyroid;
-Divided into lobules of medullary (inside) and cortical (outside) tissue;
-Prominent at birth, grows until puberty, then regresses to fat and connective tissue
What is the most important role of the Thymus?
-Producing T-lymphocytes of immunity and hormones that stimulate them;
-Probably the link between leukemia stimulus and disease
What is Myasthenia?
Neuromuscular disease associated with Thymic tumors
What is the function of the the Thymus?
-Seeds lymph nodes with activated t-lymphocytes late in fetal life;
-Secretes several immune system hormones =
1. Thymopoietin I and Thymopoietin II – promote the TRANSFORMATION of lymphocytes into T cells
2. Thymosin – may promote the MATURATION of T lymphocytes
What is Acquired Immune Deficiency Syndrome (AIDS)?
-Caused by the virus Human Immunodeficiency Virus (HIV);
-Has increased the overall adult mortality rate in the U.S. in men by 0.7% and in women by 0.07%;
-Much more deadly in Africa
Who is at “high risk” for acquiring AIDS?
1. Homosexual and bisexual men
2. IV drug users
3. People who received a blood transfusion prior to 1985
4. Women who have had sexual relations with men at high risk (Haiti and Central Africa)
5. Children infected IN UTERO by women with the virus
What are the labs tests for AIDS?
-Counting the number of Helper to Suppressor T cells by counting ANTIGENS on their surface;
1. Helper T cells – T4 antigen;
2. Suppressor and Cytotoxic T cells – T8 antigen
What results indicate AIDS?
-Normal person – T4/T8 antigen ratio > 1
-Person with AIDS – T4/T8 antigen ratio 0.5 or lower
What is the health effects of AIDS?
Causes reduced immunological function and increased susceptibility to OPPORTUNISTIC INFECTIONS SUCH as:
-Pneumocystis carinii pneumonia
-Kaposi’s sarcoma – rare form of cancer
Treatment – cocktail of expensive drugs which maintain immune function
What are the Adrenal Glands?
-Two pyramid shaped structures lying close to the upper pole of each kidney;
-Composed of two functionally distinct regions
1. Medulla – central region, cells derived from cells that embryologically split off from the neural crest
2. Cortex –surrounding zone of tissue, 8-9 times larger than the medulla, derived from cells that also gave rise to the gonads (steroid hormones)
What is the function of the Adrenal MEDULLA?
-Secretes two hormones → numerous physiological effects
-Combo of Epi + NE = ADRENALINE ;
-Controlled by the sympathetic branch of the autonomic nervous system;
-Cathelcolamines = comes from amino acids — require Tyr and Phe
What are the effects of Epinephrine from the Adrenal Medulla?
-Hormonal effects of Epinephrine last 10X longer than Norepinephrine;
-Innervated by preganglionic Sympathetic fibers;
-Activated during "fight or flight" response
1. Increased respiratory rate
2. Increased HR & cardiac output
3. General vasoconstriction which increases venous return
4. Glycogenolysis (glycogen to glucose) & lipolysis (breakdown fat)
What is produced by the Adrenal Cortex?
Adrenal cortex → corticosteroids
-Necessary for life
-Produces STEROID hormones;
-Controlled by ACTH from the adenohypophysis (Anterior lobe of the Pituitary)
What are the 3 groups of Corticosteroids?
1. Androgens – cause masculinizing effects; male secondary sex characteristics
2. Glucocorticoids – affect fat, pro, and CHO metabolism
3. Mineralocorticoids (Aldosterone) – control electrolyte balance of Na+, Cl- , and K+
*Total 28 different hormones
What is the function of Glucocorticoids?
-Not well understood;
-Most abundant is Hydrocortisone;
-Other are cortisone and corticosterone
What is the effect Hydrocortisone on Protein Metabolism?
Increases free AAs in the extracellular fluid and causes increased rates of the use of these AAs
What is the effect Hydrocortisone on Fat Metabolism?
Mobilizes fat from the fat deposits resulting in a decrease in the amount of fat in storage areas and an increase utilization of fat for energy
What is the effect Hydrocortisone on Glucose Metabolism?
-Increases blood glucose levels;
-Acts on fat and protein in liver to increase blood glucose levels = Gluconeogenesis
What is the function of Mineralocorticoids?
One of them is Aldosterone:
- Increases reabsorption of Na+ from kidney tubules to the blood;
-Which leads to decreased K+ reabsorption;
-Increases reabsorption of Cl- by kidney tubules
What the General Adaptation Syndrome (GAS)?
-Stress induces a non-specific response called general adaptation syndrome (GAS);
-Causes ACTH (adrenocorticotropic hormone) & cortisol release = release of hormones from adrenal cortex;
-Often affects physiology negatively
What is the Pancrease?
-Exocrine → digestive enzymes and HCO3 = mostly!;
-Endocrine → Islets of Langerhans →insulin and glucagon
What is Insulin’s role in CHO metabolism?
-Released from β cells by elevated blood glucose;
-Tyrosine Kinase second messenger system;
-Stimulates facilitated diffusion of glucose into cells via Glut transporters into the cell membrane;
-Increases the conversion of glucose to glycogen in the liver and muscle;
-Increases the oxidation of glucose by tissues;
-Increases the conversion of carbohydrate to fat and protein
What are the Islets of Langerhans?
-Scattered clusters of endocrine cells in pancreas;
-Contain alpha & beta cells
-Alpha = Glucagon
-Beta = Insulin
When is Insulin released?
-Betas secrete insulin in response to high blood glucose;
-Promotes entry of glucose into cells;
-& conversion of glucose into glycogen & fat;
-Decreases blood glucose
When is Glucagon released?
-Alphas cells- secrete glucagon in response to low blood glucose;
-Stimulates glycogenolysis & lipolysis;
-Increases blood glucose
Where are the sex hormones produced?
-Gonads (testes & ovaries) secrete steroid hormones testosterone, estrogen, & progesterone;
-Under the control of LH (luteinizing) and FSH (follicle stimulating) = Negative feedback
What are the Placental Hormones?
1. Human chorionic gonadotropin (hCG)
4. Human somatomammotropin (hCS)
What is Human chorionic gonadotropin (hCG)?
Promotes growth of the corpus luteum and secretion of estrogen and progesterone;
-Concentration peaks at about 8 weeks gestation;
-In a male fetus — stimulates growth of external sex organs
What is Estrogen?
Promotes growth of the mother’s sex organs and some fetal tissue
What is Progesterone?
Promotes development of some fetal tissues and organs’
-Helps promote development of secretly apparatus of the mother’s breast
What is Human somatomammotropin (hCS)?
Promotes increased fat breakdown and fatty acid release from adipose tissue in the moth and promotes the sparing of glucose for use by the fetus
What hormone is secreted by the Stomach?
GASTRIN — when food enters the stomach;
-Absorbed into the blood and stimulates gastric glands;
-Mostly PARIETAL cells - HCL secretion increased 8x;
-Also CHIEF cells — digestive pepsinogen increased 2-4x
What hormone is secreted by Adipose Tissue?
LEPTIN — acts as a satiety factor the reduce appetite and increase the bodies caloric expenditure
What hormones are secreted by the Intestine?
-Gastric inhibitory peptide
What is Secretin (intestinal)?
-Food in SI releases prosecretin into the blood;
-Converted to secretin in the blood;
-Causes the pancreas to release bicarbonate (HCO3-) ions to buffer acid from stomach
What is CCK (intestinal)?
-Food enter SI;
-Release of PANCREATIC digestive enzymes;
-Gallbladder contraction and release of bile
What is Gastric Inhibitory Peptide (intestinal)?
-When fatty food enters the duodenum too fast;
-Inhibits the pyloric sphincter from opening so that food is stays in the stomach longer
What is Enterocrinin (intestinal)?
Stimulates the release of enzymes from the intestinal mucosa
What is Guanylin (intestinal)?
From cells of the ileum and coon and stimulates the intestinal secretion of Cl-, causing elimination of NaCl and H2O in feces
What are the kidney hormones?
1. Juxtaglomerular apparatus→ RENIN – angiotensin system
2. Erythropoietin — when the kidney becomes HYPOXIC (oxygen depleted); targets tissue bone marrow to cause erythropoiesis
What is the hormone released from the Heart?
Atria secretes Atrial Natiuretic Peptide;
-Due to elevated blood volume;
-Increases excretion of NaCl and water by preventing reabsorption from nephrons of the kidney
What are Autocrine Regulators?
-Produced & act within SAME tissue of an organ;
-All autocrines control gene expression in target cells
What are Paracrine Regulators?
-Autocrines that are produced within one tissue & act on DIFFERENT tissue in same organ.
What are some Autocrine and Paracrine Regulators?
1. Cytokines (lymphokines, interleukins)
2. Growth factors (promote growth & cell division)
3. Neutrophins (provides trophic support for normal & regenerating neurons)
What are Prostaglandins?
-Produced in almost every organ ;
-Belong to EICOSANOID family -- all derived from arachidonic acid of cell membrane
What are the functions of Prostaglandins?
-Wide variety of functions;
-Different PGs may exert ANTAGONISTIC effects in tissues =
--Some promote smooth muscle contraction & some relaxation;
--Some promote clotting; some inhibit
-Promotes inflammatory process of immune system;
-Plays role in ovulation;
-Inhibits gastric secretion in digestive system