Endocrine System Flashcards
endocrine glands
- synthesize and secrete chemical substances called hormones into the circulatory system
- ex: pituitary, hypothalamus, thyroid, parathyroid, adrenals, pancreas, testes, ovaries, pineal gland, kidneys, gastrointestinal glands, heart, and thymus
exocrine glands
- secrete substances transported by ducts
- ex: gallbladder
adrenal glands
- sit on top of the kidneys
- consist of adrenal cortex and adrenal medulla
adrenal cortex
-adrenocoticotropic (ACTH) stimulate the adrenal cortex to produce adrenocortical steroids or corticosteroids
corticosteriods
- bound to transport proteins called transcortins
- reduce immune system
glucocorticoids (AC)
- cortisol and cortisone
- raise blood glucose levels by promoting the breakdown and gluconeogenesis and decreasing protein synthesis
- anti-inflammatory effects
mineralocorticoids (AC)
- aldosterone: active reabsorption of Na and passive reabsorption of water in the nephron, increasing blood volume and pressure
- regulate plasma levels of Na and K and total extracellular water volume
cortical sex hormones (AC)
- androgens (male sex hormones)
- testes in men
- in women, overproduction can cause masculinity
adrenal medulla
-produces epinephrine and norepinephrine, both with belong to catecholamine (AA derived compounds)
epinephrine
- increases conversion of glycogen to glucose, causing increase in blood glucose levels and increase in basal metabolic rate
- increase heartbeat and constrict blood vessels
- “fight or flight”
pituitary gland
- hangs below the hypothalamus and is connected to it by a cord known as the infundibulum
- pituitary (hypophysis) is a small, trilled gland at the base of the brain
anterior pituitary
-synthesizes direct hormone and tropic hormones (stimulate other endocrine glands to release hormones)
direct hormones include
- growth hormone
- prolactin
- endorphins
- melanocyte-stimulating hormone
GH (somatotropin)
- promotes muscle and bone growth
- deficiency can lead to dwarfism, overproduction to gigantism
- overproduction in adults leads to acromegaly (disproportionate growth of bones)
prolactin
-stimulates milk production
endorphins
neurotransmitters with pain-relieving properties
melanocyte-stimulating hormone
-releases melanin
tropic hormones include
- adrenocorticotropic hormone
- thyroid-stimulating hormone
- luteinizing hormone
- follicle-stimulating hormone
adrenocorticotropic hormone
-stimulates adrenal cortex to stnthesize glucocorticoids
thyroid-stimualting hormone
-stimulates thyroid to synthesize thyroxine
luteinizing hormone
-stimulates ovulation and formation of corpus luteum
follicle-stimulating hormone
-causes maturation of follicles that secrete estrogen, maturation of seminiferous tubes and sperm production
posterior pituitary
- does not synthesize hormones
- stores and releases peptide hormones oxytocin and antidiuretic hormone
oxytocin
-increases strength of uterine muscle contractions
antidiuretic hormone (vasopressin)
- increases permeability go collecting duct to water, increases blood volume and pressure
- secreted when plasma osmolarity increases
hypothalamus
- part of forebrain and located above pituitary gland
- receives transmissions from brain that triggers responses from its neurosecretory cells
hypothalamus and anterior pituitary
-hypothalamic-releasing hormones stimulate or inhibit secretions of anterior pituitary
hypothalamus and posterior pituitary
-neurosecretory cells synthesize oxytocin and ADH and transport them to the posterior pituitarY
thyroid
- hormones in the thyroid are essential for growth and maintenance of metabolic stability
- thyroxine and triiodothyronine, formed from thyroglobulin
thyroxine (T4)
- transported via plasma proteins
- all is formed and secreted by the thyroid gland
triiodothyronine (T3)
- more potent than T4
- 20% is produced by the thyroid gland
- majority is produced from the conversion of T4 to T3 by 5’-monodeiodase
hypothyroidism
- thyroid hormones are under secreted or not secreted at all
- in infants: cretinism is characterized by intellectual disability
hyperthyroidism
-thyroid is overstimulated
calcitonin
-decreases plasma Ca2+ by inhibiting the release of
Ca2+ from bone
pancreas
- exocrine and endocrine organ
- exocrine function performed by cells that secrete digestive enzymes
- endocrine function performed by islets of Langerhans, composed of alpha and beta cells
glucagon
stimulates protein and fat degradation and conversion of glycogen to glucose, increasing blood glucose levels
insulin
secreted in response to high blood glucose concentration, lowers blood glucose levels
diabetes mellitus
underproduction of insulin or insensitivity to insulin causes this
-characterized by hyperglycemia (high blood glucose levels)
parathyroid glands
- 4 pea-shaped structures embedded in the posterior surface of the thyroid
- synthesize parathyroid hormones, which regulates plasma Ca2+ concentration
kidneys
- produce renin: an enzyme that converts plasma protein angiotensinogen to angiotensin 1 then converted to angiotensin II to stimulate adrenal cortex to produce aldosterone
- produces erythropoietin that stimulates RBC production
gastrointestinal hormones
- gastrin: stimulates glands to produce HCl
- secretin: released by small intestine when acidic food enters stomach, neutralizes chyme
- cholecystokinin: released by small intestine in presence of fats and release bile
pineal gland
-structure at the base of the brain that secretes melatonin, which plays a role in circadian rhythms- physiological cycles
peptide hormones
- first messengers, bind to specific receptors and trigger enzymatic reactions
- conversion of ATP to cAMP, which acts as a second messenger (cascade effect)
steroid hormones
- class of lipid-derived molecules
- cross the phospholipid bilayer and enter their target cells directly to bind to receptors
