Endocrinology Flashcards
Adrenal Gland
On top of kidney. Made up of Adrenal Cortex and Adrenal Medulla
Adrenal Cortex
When stimulated by stress ACTH hormone produces more than two dozen different steroid hormones, adrenocortical steroids. These are bound to transcortin proteins.
Glucocorticoids
Cortisone and cortisol are involved in glucose regulation and protein metabolism. Raise blood glucose levels by promoting protein breakdown and gluconeogenesis and decreasing protein synthesis. Release amino acids from skeletal muscles and lipids from adipose tissue.
Mineralocorticoids
Aldosterone, regulate plasma levels of sodium and potassium and regulate the total extracellular water volume. Causes active reabsorption of sodium and passive reabsorption of water in the nephron of the kidney –> increase in blood volume and blood pressure
Cortical Sex Hormones
Adrenal cortex secretes small amount of androgens, not a significant amount compared to testes for men so little effect on men. Can have significant effect on women if there is overproduction
Adrenal Medulla
Processes epinephrine and norepinephrine (both catecholamines)
Epinephrine
Increases the conversion of glycogen to glucose in the liver and muscle tissue–> increase in blood glucose levels, increase in basal metabolic rate. Increase heart rate, dilate and constrict blood vessels in such a way to increase blood supply to muscles, heart and brain and decrease blood supply to kidneys, skin and digestive tract. Inhibits certain vegetative functions that are not immediately important for survival.
Norepinephrine
Increase heart rate, dilate and constrict blood vessels in such a way to increase blood supply to muscles, heart and brain and decrease blood supply to kidneys, skin and digestive tract.
Release of Norepinephrine and Epinephrine
Stimulated during sympathetic activation by sympathetic preganglionic fibers, by the sympathetic nervous system in response to stress.
Pituitary Gland
small, trilobed gland at base of brain. Anterior and Posterior= two main lobes. Hangs below hypothalamus and is connected by the infundibulum.
Anterior Pituitary
Synthesizes direct hormones and tropic hormones. Hormone secretions are regulated by the hypothalamic secretions, the inhibiting/releasing factors
Direct Hormones
Anterior Pituitary. Directly stimulate target organs. Growth hormones, Prolactin.
Growth Hormones
Direct. Promotes bone and muscle growth, promotes protein synthesis and lipid mobilization and catabolism.
Acromegaly
Overproduction of GH in adults, disorder characterized by disproportionate overgrowth of bone, localized in the skull, jaw, feet, and hands.
Prolactin
Direct. stimulates milk production and secretion in female mammary glands.
Tropic Hormones
Anterior Pituitary. Stimulate other endocrine glands to release hormones. ACTH, TSH, LH, FSH, MSH, Endorphines.
ACTH (Adrenocorticotropic)
Tropic. Stimulates the adrenal cortex to synthesize and secrete glucocorticoids and is regulated by the releasing hormone corticotrophin-releasing factor.
TSH (Thyroid-Stimulating)
Tropic. Stimulates the thyroid gland to synthesize and release thyroid hormones. (thyroxin)
LH (Luteinizing)
Tropic. Women: stimulates ovulation and formation of corpus luteum, regulate progesterone secretion. Men: stimulates interstitial cells of the testes to synthesize testosterone.
FSH (Follicle-stimulating)
Tropic. Women: causes maturation of ovarian follicles that begin secreting estrogen. Men: stimulates maturation of the seminiferous tubules and sperm production.
MSH (Melanocyte-stimulating)
Tropic. Secreted by the intermediate lobe of the pituitary. Function unknown in mammals. In frogs causes darkening of skin via induced dispersion of molecules of pigment in melanophore cells
Endorphines
Tropic. Neurotransmitters that have pain-relieving properties.
Posterior Pituitary
Neurohypophysis. Does not synthesize hormones, stores and releases peptide hormones (oxytocin and antidiuretic hormone). Stimulated by action potentials descending from the hypothalamus.
Oxytocin
Posterior Pituitary. Produced by neurosecretory cells of hypothalamus. Secreted during childbirth, increases strength and frequency of uterine muscle contractions, induced by suckling to stimulate milk secretion in mammary glands.
Antidiuretic Hormone (ADH; vasopressin)
Posterior Pituitary. Increases the permeability of the nephron’s collecting duct to water promoting water reabsorption and increasing blood volume which increases blood pressure. Is secreted when plasma osmolarity increases as sensed by osmoreceptors in hypothalamus or when blood volume decreases as sensed by baroreceptors in the circulatory system.
Hypothalamus
Part of forebrain, directly above pituitary gland. Receives neural transmissions from other parts of the brain, from peripheral nerves that trigger specific responses from its neurosecretory cells.
Neurosecretory Cells
Regulate pituitary gland secretions via negative feedback mechanisms and through the actions of inhibiting and releasing hormones.
Hypothalamus with Anterior Pituitary
Stimulate or inhibit the secretions of anterior pituitary: GNRH stimulates it to secrete FSH and LH. Releasing hormones are secreted into the hypothalamic hypophyseal portal system. There the blood from the capillary bed in the hypothalamus flows through portal vein into the anterior pituitary and diverges into another capillary network. This allows releasing hormones to immediately reach the anterior pituitary
Hypothalamus with Posterior Pituitary
Neurosecretory cells in the hypothalamus synthesize both oxytocin and ADH and transport them via their axons into the posterior pituitary for storage and secretion.
Thyroid Hormones
Affect the function of nearly every organ system in the body. Kids: essential for growth and development. Adults: essential for maintenance of metabolic stability. Thyroxine (T4) and triiodothyronine (T3)
Thyroxine
T4. Synthesized in thyroid cell. Transported in the blood by TBG, TBPA and albumin. All of T4 in body is formed and secreted by thyroid gland. Derived from the iodination of the amino acid tyrosin.
Triiodothyronine
T3. Synthesized in thyroid cell. Transported in the blood by TBG, TBPA and albumin. Five times more potent than T4. 20% of T3 is produced by the thyroid gland. Majority of T3 is produced by the conversion of T4 to T3 by the enzyme 5’-monodeiodase, found mainly in the peripheral tissues. Derived from the iodination of the amino acid tyrosin.
Hypothyroidism
Thyroid hormones are under-secreted or not secreted at all. Symptoms: slowed heart rate and respiratory rate, fatigue, cold intolerance, and weight gain. Thyroid often enlarges and forms a bulge in the neck called a goiter.
Cretinism
Hypothyroidism in infants, mental retardation and short stature.
Hyperthyroidism
Thyroid is overstimulated, resulting in over-secretion of thyroid hormones. Increased metabolic rate, feelings of excessive warmth, profuse sweating, palpitations, weight loss, and protruding eyes. Thyroid often enlarges and forms a bulge in the neck called a goiter.
Calcitonin
Decreases plasma calcium concentration by inhibiting the release of calcium from bone. Secretion of calcitonin is regulated by plasma calcium levels. Antagonistic to parathyroid hormones.
Pancreas
Exocrine and endocrine organ.
Pancreas- Exocrine
Cells secrete digestive enzymes into the small intestine via a series of ducts.
Pancreas- Endocrine
Small glandular structures called the islets of Langerhans which are composed of alpha and beta cells.
Alpha cells of Islets of Langerhans
Pancreas. Produce and secrete glucagon.
Beta cells of Islets of Langerhans
Pancreas. Produce and secrete insulin.
Glucagon
Stimulates protein and fat degradation, conversion of glycogen to glucose, and gluconeogenesis all of which increase blood glucose levels. Actions are largely antagonistic to insulin.
Insulin
Protein hormone secreted in response to a high blood glucose concentration. Stimulates uptake of glucose by muscle and adipose cells and the storage of glucose as glycogen in muscle and liver cells, lowering blood glucose levels. Stimulates synthesis of fats from glucose and the uptake of amino acids.
Parathyroid glands
four small pea shaped structures on surface of thyroid. Synthesize and secrete parathyroid hormone. Regulates plasma and calcium concentrations, raises calcium conc in blood by stimulating release of it from bones and decreasing calcium excretion in kidneys.
Kidneys
When blood volume falls the kidneys produce renin. Also produce erythropoietin (EPO)
Renin
In kidneys. Enzyme that converts plasma protein angiotensinogen to angiotensin I which converts to angiotensin II, this stimulates adrenal cortex to secrete aldosterone.
Aldosterone (Kidneys)
Helps to restore blood volume by increasing sodium reabsorption at the kidney leading to an increase in water. Removes the initial stimulus for renin production.
Erythropoietin (EPO)
Kidneys. Glycoprotein that stimulates red blood cell production; it is normally produced in the kidneys. Causes stems cells to differentiate into ruriblasts, increased rate of mitosis, increased release of reticulocytes from bone marrow, increased hemoglobin formation allowing critical HgB concentration necessary for maturity to be reached at more rapid rate
Gastrointestinal hormones
Gastrin, secretin, cholecystokinin
Gastrin
Stomach is stimulated to release when food is ingested. Carried to the gastric glands and stimulates the glands to secrete HCl in response to food in the stomach.
Secretin
Released by the small intestine when acidic food material enters from the stomach. Stimulates the secretion of an alkaline bicarbonate solution from the pancreas that neutralizes the acidity of the chyme.
Cholecystokinin
Released from small intestine in response to the presence of fats and causes the contraction of the gall bladder and release of bile into the small intestine.
Bile
Bile is involved in the emulsification and digestion of fats.
Pineal Gland
tiny structure at the base of the brain that secretes the hormone melatonin
Melatonin
Unclear role, believed to partake in the regulation of circadian rhythms (physiological cycles lasting 24 hours), secretion is regulated by light and dark cycles in the environment.
Peptide Hormones
Simple short peptides (amino acid chains) to complex polypeptides (e.a. insulin). Act as first messengers, bind to specific receptors on surface of target cells, trigger enzymatic reactions in each cell
ATP to cAMP
Peptide reaction. Possible first enzymatic reaction after peptide binds to specific receptor, catalyzed by membrane-bound enzyme adenylate cyclase. cAMP acts as a second messenger, relaying messages from the extracellular peptide hormone to cytoplasmic enzymes initiating a series of successive reactions in the cell. (cascade effect)
Steroids
estrogen and aldosterone, lipid-derived molecules with a characteristic ring structure. Lipid soluble so cross phospholipid bilayer and enter their target cells directly in order to bind to specific receptor proteins in the cytoplasm. Receptor-hormone complex enters the nucleus and directly activates the expression of specific genes by binding to receptors on the chromatin, induces a change in mRNA transcription and protein synthesis
