endocrine system Flashcards
what are the organs in the endocrine system?
endocrine glands- release hormones into blood
what are the general functions?
- maintains homeostasis by negative feedback regulation
- regulates growth and metabolism
- works closely with the nervous system
what are the differences between the endocrine vs nervous system?
1.chemical messenger:
endocrine: hormones
nervous: neurotransmitter
2. site of action:
endocrine: widespread (circulation)
nervous: localized (synapse)
3. nature of responce:
endocrine: slow + long term
nervous: rapid +short term
what are the 3 mechanisms of action to stimulate the endocrine glands?
- humoral stimuli- in blood
- neural stimuli- ans
- hormonal stimuli- pituitary hormones
what do all three mechanisms to stimulate the endocrine do?
secretion of hormones into the blood
what happens once the secretion of hormones into the blood?
- hormone circulates freely
- hormone binds to carrier protein
which reaches the target cells and hormone binds to receptor in responce
what is a hormone half-life?
time for half of circulating hormone to be examined
typically less then 1minute to 60 min
how does hormone inactivation occur?
binds to receptor in target cell
metabolized in liver/excreted by kidneys
broken down by enzymes in the blood/tissue fluid
what is the structure of a lipid hormone?
- steroid hormone derived from cholesterol
eg estrogen, progesterone, testosterone, cortisol - eicosanoids derived from arachidonate
eg, prostaglandins, leukotriennes(associated with inflammation)
paracrine hormones
chemical messengers released by cells into tissue fluid diffuses to nearby cells and has local effects only
what is the structure of peptide hormone?
peptides are small proteins
most hormones (GH, TSH, FSH, LH, ADH)
what is the structure of amino acid derived hormones?
small molecules called monoamines
eg. melatonin, thyroid hormones, epinephrine
includes norepinehprine and dopamine which can be released into the blood
what are membrane bound recpetors?
membrane bound receptors
- location in cell membrane
-bind hydrophillic hormones (cannot pass through the lipid bilayer)
-eg. most peptide and amino acid hormones
what are intracellular receptors?
location- cell cytoplasm or cell nucleus
bind to hydrophobic hormones can pass through the phospholipid bilayer
- eg steriod hormones and thyroid hormone
what is the mechanism of action of a peptide/ monoamine hormone?
1.transported freely in blood
2. bind to receptor on membrane of target cell activate second messenger via G protein
what is the mechanism of action of steroid hormones?
- carried by transport protein in blood
- diffuse into target cell and bind to intracellular receptor
- activates enzymes or genes
what are possible effects of hormones on target cells?
- open or close ion channels/transporters
- stimulate protein synthesis in target cells
- activate/inactivate enzymes
- induce secreation
- stimulate mitosis
how does the hypothalamus regulate the endocrine system?
secretes hormones that regulate anterior pituitary function
what are the hormones the hypothalamus secretes?
RH- releasing hormones
stimulate synthesis or secretion of anterior pituitary hormones
IH- inhibatory hormones
inhibits synthesis of secretion of anterior pituitary hormones
what are both hormones of the hypothalamus transported by?
RH and IH hormones transported via hypophyseal portal vein directly to pituitary
how does the pituitary regulate endocrine system?
hypophysis
master endocrine gland- secretes many tropic hormone
what is a tropic hormone?
hormone that regulates function of another endocrine gland
what is the anterior pituitary?
adrenohypophysis
glandular tissue compromised of 5 types of cells
these cells secrete a total of 7 hormones
what is the growth hormone? target and effect
GH or somatotropin
target: most cells especially liver
effects: stimulates growth by stimulating the liver to secrete sommatomedins to increase protein sysnthesis, bone growth
also affects fat/carbohydrate metabolism
what is the hypothalamic regulation of GH?
GH-IH inhibits GH release
GH-RH stimulates GH release
what is the TSH?
thyroid stimulating hormone or thyrotropin
target- thyroid gland
effects- stimulates thyroid to release TH thyroid hormone
hypothalamic regulation- TRH stimulates TSH release
what is FSH?
follicle stimulating hormone
target- ovaries and testes
effects- stimulates maturation of gametes sperm and egg
hypothalamic regulation- Gn-RH stimulates FSH release
Gn-IH inhibits inhibits FSH relaease
what is LH?
luteninzing hormone
target- ovaries and testes
effects- in females stimulates ovulation and progesterone production, in males stimulates testosterone production
hypothalamic regulation- Gn-RH sitmulates LH release
Gn- IH inhibits LH release
what is ACTH?
adrenocorticotropic hormone or corticotropin
target- adrenal cortex
effect- stimulates adrenal cortex to release glucococoticoid hormones aka cortisol
hypothalamic regulation- CRH stimulates ACTH release
what is MSH?
melanocyte stimulating hormone
target-melanocytes
effects- increases production of melanin
levels are low in humans so not really understood
what is PRL?
Prolactin
target- mammary glands
effects- stimulates milk prodcution
hypothalamic regulation- PRF prolactin releasing factor
PIH- prolactin inhibiting hormone
what is the posterior pituitary?
neurohypophysis
neural tissue not epithelial or glandular
stores 2 neurohormones- produced in hypothalamus transported along axons to posterior pituitary
what is ADH?
Antidiuretic hormoner or vasopressin
target- kidneys tubules
effects- stimulates water and na+ reabsorption- concent
by movement of water = osmosis and retains sodium
alcohol inhibits ADH release
what is OT?
oxytocin
target- smooth muscle in reproductive organs
effects- in female triggers uterine contraction during childbirth and intercourse and mammary glands to let down milk in nipple
in male propels semen through reproductive tract during ejaculation
is also important in bonding/attachment love hormone
what are the two hormones in thyroid?
TH and calcitonin
what is TH
thyroid hormone
t3 triiodothyronine
t4 thyroxine
both made from protein thyroglobulin and contains iodine
secreted by follicle cells in responce to TSH
t4 is converted to t3 becuase it is the biologically active form of TH
target and effects of TH?
target- most cells
effects- increases the metabolic rate
increases protein/fat/carb metabolism, heat production, heart rate and affects growth/development
what is different about TH peptide hormone?
is peptide hormone but iodine makes it lipophillic and it requires a transport protein and it binds to intraceellular receptors
what is calcitonin?
thyrocalcitonin
target- bone and kidneys
effects- decreases ca++ levels in the blood which inhibits osteoclasts and increases excretion of ca++ in urine
what is PTH?
parathyroid hormone
target- bone and kidneys
effects- increases ca++ levels in the blood which increases osteoblast activities so increases bone breakdown
reduces calcium excretion in the urine
activates vitamin d to d3 and increases absoprtion of dietary calcium
what are the two components to the adrenal glands?
outer adrenal cortex and inner adrenal medulla
what is aldosterone?
in adrenal cortex is mineralcorticoid
target- kidneys
effect- na+ reabsorption which increases water reabsorption and concentrates the urine and raises blood pressure
also affects k+ levels in na+/k+ exchange pump
what is cortisol?
glucocotircoid in adrenal cortex
target- most cells
effect- is secreted in responce to stress reduces inflammation alters metabolism of protein and fats and suppresses the immune system
what is androgens?
gonadocorticoids in adrenal cortex
adrenal cortex is also a source of sex hormone
eg testosterone in females and estrogen after menopause
what is epinephrine/ norepinephrine?
in adrenal medulla
target- most cells
effects- activates sympathetic division of ANS flight fright flight responce
increases levels with chronic stress
what are the two hormones of the pancreas?
insulin and glucagon
where do the endocrine cells (alpha and beta) reside?
located in pancreatic islets
what is insulin?
target- most cells
effects-decreased blood glucose by stimulating blood glucose transport into cells
also increases protein , glycogen, and fat synthesis
what happens in a insulin production deficiency?
secreted by beta cells
destruction of beta cells results in type 1 diabetes and type two occurs when the body becomes unresponsive to insulin
what is glucagon??
secreted by alpha cells
target- liver mainly, adipocytes
effects- increase blood glucose
by stimulating breakdown of glycogen and increasing synthesis of glucose by liver
what is the thymus?
secretes hormones involved in development of immune cells T-lymphocytes
T-lymphocytes mature in the thymus gland
most active during fetal development and childhood and shrinks with age
what is the pineal gland?
location- epithalamic region of brain
secretes hormone melatonin
function- regulate light and dark cycles, potent antioxident, regulation of reproduction
