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