Chapter 19 Health Alt Flashcards
What does insulin do?
-Insulin helps blood sugar enter the body’s cells so it can be used for energy.
-Insulin also signals the liver to stroke blood sugar for later use.
-Blood sugar enters cells, and levels in the bloodstream decrease, signaling insulin to decrease too.
-Insulin moves glucose from your blood into cells all over your body.
-(Think of insulin as the “key” that opens the “doors” of the cells in your body)
-stimulated by chemical, hormonal, neural and by parasympathetic NS (b4 meals)
Pancreas does what?
Has both endocrine (produces hormones) and exocrine (produces digestive enzymes) functions.
The pancreas houses islets of Langerhans which have 4 types of hormone-secreting cells, which are
Alpha cells ->which secrete glucagon
Beta cells -> which secrete insulin and amylin
Delta cells -> which secrete gastrin and somatostatin
F (or PP) cells ->which secrete pancreatic polypeptide
These hormones regulate carbohydrate, fat, and proteinmetabolism.
what do the parathyroid glands do?
They produce parathyroid hormone (PTH) which helps:
-Increases serum calcium and decreases serum phosphate
-Promotes calcium and phosphate absorption to enhance bone mineralization
-Vitamin D (cofactor) needed for PTH function
pineal gland
-Secretes melatonin
-regulates circadian rhythms
-regulates reproductive systems
-secretion of gonadotropin-releasing hormones
Posterior Pituitary
produces two hormones:
-antidiuretic hormone (ADH) which controls plasma osmolality
-oxytocin which causes uterine contractions, milk ejection in lactating women, and may affect sperm motility in men.
Anterior Pituitary
Tropic Hormones:
-Promotes secretion of melanocyte-stimulating hormone (MSH)
Glycoprotein Hormones:
-Follicle-stimulating hormone (FSH)
-Luteinizing hormone (LH)
-Adrenocorticotropic hormone ACTH)
-Thyroid-stimulating hormone (TSH)
Somatotropic Hormones:
-Growth hormone (GH)
-Prolactin
Anterior Pituitary Hormones regulated by:
The anterior pituitary hormones are regulated by (1) secretion of hypothalamic releasing factors, (2) feedback effects of the hormones secreted by target glands, and (3) direct effects of other mediating neurotransmitters.
Why are hormones released?
-In response to an alteration in the cellular environment
-To maintain a regulated level of certain substances or other hormones
The endocrine system functions:
-Differentiation of reproductive system and CNS in fetus
-Stimulation of growth and development
-Coordination of the male and female reproductive systems
-Maintenance of internal environment
-Adaptation to emergency demands of body
Beta cells from the pancreas synthesize:
Insulin
-Synthesized from proinsulin
-Secretion is promoted by increased blood levels of glucose, amino acids, GI hormones
-Facilitates the rate of glucose uptake into the cells
-Anabolic hormone
->Synthesis of proteins, lipids, and nucleic acids
-Insulin secretion diminishes in response to low blood levels of glucose (hypoglycemia), high levels of insulin (through negative feedback to the beta cells), and sympathetic stimulation of the beta cells in the islets.
Amylin
-Peptide hormone co-secreted with insulin
-Delays gastric emptying (regulates blood glucose concentrations by delaying gastric emptying and suppressing glucagon secretion after meals)
-Suppresses glucagon secretion
-has a satiety affect which reduces food intake
Alpha cells in the pancreas stimulates:
Glucagon (antagonistic to the effects of insulin):
-Secretion is promoted by decreased blood glucose levels
-Stimulates glycogenolysis, gluconeogenesis, and lipolysis
Delta cells in the pancreas stimulates: Somatostain and Gastrin
Somatostatin:
-Somatostatinis produced by delta cells of the pancreas in response to food intake and is essential in carbohydrate, fat, and protein metabolism.
-It is different from hypothalamic somatostatin, which inhibits the release of growth hormone and TSH. -Pancreatic somatostatin is involved in regulating alpha-cell and beta-cell function within the islets by inhibiting secretion of insulin, glucagon, and pancreatic polypeptide.
Gastrin:
- Pancreatic gastrin stimulates the secretion of gastric acid. It is postulated that fetal pancreatic gastrin secretion is necessary for adequate islet cell development.
F (PP) Cells in the pancreas produce: Pancreatic polypeptide
-Pancreatic polypeptideis released by F cells in response to hypoglycemia and protein-rich meals. It inhibits gallbladder contraction and exocrine pancreas secretion and is frequently increased in individuals with pancreatic tumors or diabetes mellitus.
Adrenal Gland
Consist of two portions
-Adrenal Cortex (outer)
-Adrenal Medulla (inner)
-Separate as separate but interrelated glands
Adrenal Cortex is subdivided into three zones:
1.Thezona glomerulosa, the outer layer, constitutes about 15% of the cortex and primarily produces the mineralocorticoid aldosterone.
2.Thezona fasciculata, the middle layer, constitutes 78% of the cortex and secretes the glucocorticoids cortisol, cortisone, and corticosterone.
3.Thezona reticularis,the inner layer, constitutes 7% of the cortex and secretes mineralocorticoids (aldosterone), adrenal androgens and estrogens, and glucocorticoids.
Adrenal cortex cells are stimulated by:
-The cells of the adrenal cortex are stimulated by ACTH from the pituitary gland.
-All hormones of the adrenal cortex are synthesized from cholesterol.
-The best-known pathway of steroidogenesis involves the conversion of cholesterol to pregnenolone, which is then converted to the major corticosteroids.
What are glucocorticoids?
-Direct effects on carbohydrate metabolism
-Suppress immune and inflammatory reactions
-Most potent naturally occurring glucocorticoid is cortisol
-These hormones increase the blood glucose concentration by promoting gluconeogenesis in the liver and by decreasing uptake of glucose into muscle cells, adipose cells, andlymphatic cells.
Glucocorticoids affect innate immunity and inflammation through several pathways, including decreased function of macrophages and natural killer cells, suppression of inflammatory cytokines, and decreased release of proteolytic enzymes. -Psychological and physiologic stress increases glucocorticoid production, which provides a pathway for the well-described decrease in immunity seen in both acute and chronic stress conditions
-Glucocorticoids appear to potentiate the effects of catecholamines, including sensitizing the arterioles to the vasoconstrictive effects of norepinephrine, thus increasing the blood pressure.
-Other effects of glucocorticoids include inhibition of bone formation, inhibition of ADH secretion, and stimulation of gastric acid secretion.
-Cortisol is the most impo potent glucocorticoid.
-It is the main secretory product of the adrenal cortex and is needed to maintain life and protect the body from stress.
What are mineralocorticoids?
-Affect ion transport by epithelial cells
-Most potent naturally occurring mineralocorticoid is aldosterone
->Regulated by the renin-angiotensin system
-Mineralocorticoidsteroids directly affect ion transport by epithelial cells, causing sodium retention and potassium and hydrogen loss.
-Aldosteroneis the most potent naturally occurring mineralocorticoid and conserves sodium by increasing the activity of the sodium pump of epithelial cells.
-Aldosterone synthesis and secretion is regulated primarily by the renin-angiotensin system. The renin-angiotensin system is activated by sodium and water depletion, increased potassium levels, and a diminished effective blood volume. Angiotensin II is the primary stimulant of aldosterone synthesis and secretion; however, sodium and potassium levels also may directly affect aldosterone secretion.
-Aldosterone maintains extracellular volume by acting on distal nephron epithelial cells to increase reabsorption of sodium and excretion of potassium and hydrogen.
The adrenal cortex also secretes minimal amounts of estrogen and androgens.
-Adrenal estrogens and androgens
->Minimal amounts secreted
->Androgens are weak
->converted by peripheral tissues to stronger androgens such as testosterone
-Peripheral conversion of adrenal androgens to estrogens is enhanced by aging or obesity, as well as those with liver disease or hyperthyroidism.
Adrenal Medulla
-The chromaffin cells (pheochromocytes) of theadrenal medullasecrete and store the catecholamines epinephrine (adrenaline) and norepinephrine (noradrenaline).
-Only 30% of circulating epinephrine comes from the adrenal medulla (the other 70% is released from nerve terminals), and the medulla is only a minor source of norepinephrine.
-Catecholamines have diverse effects on the entire body. Their release and the body’s response have been characterized as the “fight or flight” response (stress response).
-Metabolic effects of catecholamines promote hyperglycemia through a variety of mechanisms, including interference with the usual glucose regulatory feedback mechanisms.
