basic endocrinology Flashcards
List the major endocrine glands
- hypothalamus
- pituitary gland
- thyroid gland
- parathyroid gland
- adrenal gland
- pancreas
- ovaries
- testes
definition of a hormone
- product of endrocrine galnd that is released directly into bloodstream
- acts at a distant specific target cell and exerts a biologic effect
what are the 3 methods of hormone signaling
- endocrine: hormone acts on distant tissue
- paracrine: hormone diffuses to adjacent cell
- autocrine: hormone acts on itself
neuroendocrine signaling
- hormone orginiates in the neuron and after axonal transport is carried distally
how are hormones classified
- chemical structure
- peptide
- amine
- steroids
- solubility in plasma
growth hormone, insulin and parathyroid hormones are all examples of which type of hormone
peptide hormone: dervied from amino acids
how are peptide hormones synthesized
- nucleus: DNA -> mRNA
- ribosomes: mRNA translated to preprohormone
- ER: signal peptide removed -> prohormone
- golgi: packaged in secretory vesicles and cleaved -> hormone
- vesicles: final hormone stored until endocrine cell stimulated
peptide hormone release is initiated by stimulus that involves an increase in what second messenger
- cytosolic cAMP and Ca2+
amine hormones are derived from which amino acid
tyrosine
amine hormones are secreted by what glands
- adrenal medulla
- thyroid gland
catecholamines (NE, epi, and dopamine) and thyroid hormones are examples of what type of hormone
amine hormones
amine hormone synthesized when what is activated
SNS activatation of the synthetic pathway
are amine hormones stored after synthesis?
yes, in vesicles
are steroid hormones stored after synthesis?
no
catecholamines and peptide hormones have what solubility? Thus how are they transported in the blood stream
- Hydrophilic
- transported dissolved in the blood stream
thyroid and steroid hormones have what solubility? Thus how are they transported in the blood stream
- hydrophobic
- transported bound to proteins
Name 4 importances of binding proteins
- increases half-life in plasma
- provides a reserve that can be called upon to replenish the free pool
- keeps hormone in blood inactive
- influence rate of hormone turnover
which type of hormones bind to a receptor or channel located on the outer cell membrane of the target cell
hydrophilic hormones
describe the inactivated G protein
- G protein has 3 subunits: a, B, y
- a is bound to GDP in inactivated state
list steps of Gs activation
- alpha subunit, now bound to GTP activates adenylyl cyclase
- cAMP is activated
- activation of protein kinase A
- phosphorylation of proteins
list steps of Gq pathway
- alpha subunit bound to GTP stimulates PLC (phospholipase C)
- PLC cleaves PIP2 into DAG and IP3
- DAG increases protein kinase C
- IP3 acts on ER to increase Ca2+
MOA hydrophobic hormones
- steroid diffuses into cell
- steroid binds to receptor in cytosol or in nuclues
- changes DNA transcription
what is peripheral conversion of hormones
- making something from nothing; can produce
- more active hormone
- less active hormone
- different class of hormone
- an inactive or less active form of a hormone may be secreted by an endocrine cell into the general circulation and then converted to another form by another tissue. This type of peripheral conversion occurs in blood, liver, kidney, lung, and in the target tissues of some hormones. These tissues contain enzymes capable of interconversion of hormones.
how is hormone secretion triggered
- hormonal impact
- hormones regulate the secretion of hormones
- neural stimulus
- humoral effect
what is humoral secretion of hormones
- humoral: pertaining to elements in the blood
- activated by blood-born substrate
- molecule in plasma -> concentration in plasma changes -> endocrine gland directly detects change -> endocrine gland alters secretion of molecule
what is neural secretion of hormones
- extension of CNS that signals gland to secrete hormone
- ex: fright triggers SNS which triggers release of hormones
concentration of free, bioactive hormone depends on
- secretion
- inactivation and excretion
- binding to plasma protein
- rate of activation or conversion
negative feedback
- hormone action inhibits further secretion of hormone
- most common mechanism
positive feedback
- hormone action stimulates more secretion of hormone
- least common
What is the threshold in the dose-response curve
minimal concentration of hormone required to achieve a response
What is the sensitivity in the dose-response curve
concentration of hormone that produced 50% of the maximum response
- if more [H] is required to produce 50% of the maximal response, then there is a decrease in sensitivity
what can cause a reduced maximal response
- decrease in
- number of receptors
- number of target cells
what can cause a reduced sensitivity
- a decrease in
- hormone receptor affinity
- hormone-receptor number
