endocrinology lecture 1 Flashcards
how does the endocrine system differ from the other communication system?
- routes of communication
- onset & duration of effects
what is the endocrine specificity on the target cell based on?
based on receptors on target cells
cell must contain appropriate receptor to be activated
target cells impart ________ via receptor expression
specificity
most hormones are ______
peptides (small proteins)
how does glycosylation effect the function of peptide hormones?
- help enhance specificity of hormone
- help protect hormone from degridation
t/f: some lipid hormones function as neurotransmitters as well
FALSE
its peptide hormones that can function as NT’s
what are the 3 stages of peptide hormone synthesis?
preprohormone
prohormone
hormone
what is a preprohormone? how is it made?
- 1st step of peptide hormone synthesis
- comes off ribosomes with extra AA’s, gets folded, then passes thru rough ER
- in the rough ER, the extra AA’s are cleaved
where are pre hormones sent for further processing?
- sent to golgi: packed into vesicles
any extra AA’s are cleaved in the vesicles
where are peptide hormones stored? what stimulates their eventual release?
stored in secretory vesicles
the endocrine cell being stimulated causes their release
t/f: a peptide hormone is released from the endocrine cell along with its pro-fragments
true
what is the importance of packaging and storing peptide hormones?
- gives cell a reserve of hormone
- pre, and pro, hormone steps provide regulation for cell, as well as feedback
lipid hormones are derived from what?
cholesterol
_______ determine which lipid hormone is produced
enzymes
t/f: steroid hormones are lipid hormones
true
what kinds of organs make steroid hormones?
testes, ovaries, adrenal glands, placenta, some cells in the brain
there are ______ different classes of steroids
5
cells making steroids get cholesterol from _____
LDL
steroidogenic cells have numerous _______ receptors on their plasma membranes
LDS
________ bring cholesterol into steroid-producing cells
endosomes
steroidogenic cells store cholesterol _______
esters
what is the effect of storing cholesterol esters in the steroidogenic cells?
inhibits de novo synthesis
what is the role of enzymes in steroidogenic cells?
different steroidogenic cells make different steroids based off which enzymes they have
steroid hormone synthesis is typically stimulated by what?
peptide hormones from other glands
_____________ releases cholesterol from stores within steroidogenic cells
cholesterol esterase
what protein facilitates intracellular transport of cholesterol?
StAR
steroid acute regulatory protein
cholesterol is converted to steroids by _____ enzymes in the mitochondria
P450 enzymes
cytochromes
how is steroid hormone synthesis regulated?
- upregulated by synthesis of enzymes
- regulatory peptide hormones stimulate steroid genesis
- increase in the # of steroidogenic cells
t/f: steroid hormone precursors can be stored
FALSE
they are all lipid based
what 2 enzymes are integral for steroid biosynthesis? (these were the 2 highlighted enzymes in the notes packet)
17-beta-hydroxysteroid dehydrogenase
aromatase
how are steroidogenic enzymes named?
named for the genes that encode them
most reactions of steroid biosynthesis are _____
unidirectional
during steroid biosynthesis, cholesterol is first turned into ________, a class of hormone
progestagens (progesterone)
progestagens can be converted into what other classes of hormones?
corticosteroids
androgens
estrogens
___________ are a class of hormones derived from arachanoic acid
eicosanoids
amine hormones are all derived from the amino acid _______
tyrosine
what hormones are in the “eicosanoids” class?
prostaglandins, prostacyclins, thromboxanes, leukotrienes
thyroid hormones are steroid hormones made by attaching ________, then dimerizing
iodine
what are the 2 thyroid hormones?
triiodothyronine (T3)
thyroxine (T4)
which of the thyroid hormones is more common in circulation?
T4
thyroid hormones are steroid-like with respect to _________ and ________
solubility and receptors
where are catacholamines synthesized?
in the:
adrenal gland (medulla)
hypothalamus
what hormones are in the catecholamine class
- norepinephrine (NE)
- epinephrine (E)
- dopamine (DA)
___________ are common neurotransmitters
catecholamines
catacholamines are ______-like in respect to solubilityy and reseptors
peptide-like
most hormones are secreted in _____-____
short-bursts
timing of hormone release is based on what?
upstream signals
what are examples of hormones released in a circadian pattern?
GH & cortisol
GH secreted at night, Cortisol secreted during the day
what are the 3 factors that control hormone secretion patterns?
1) plasma concentrations of a nutrient
2) neural control
3) hormonal control
______ control leads to the “short burst” secretion of hormones
neural
lipophilic hormones require ___________ to travel through the blood
carrier proteins
the use of carrier proteins affects hormone ________
availability
how are hormonal signals inactivated?
by the metabolism
- proteolytic enzymes, peptolytic enzymes
degradation of a hormone in the blood is especially a problem for water-soluble hormones, such as _________ and _______
catecholamines & peptides
where are receptors for hydrophilic hormones found?
on cell surface (on plasma membrane)
receptor activation from a hormone triggers a _____________
signal transduction pathway (2nd messenger)
what happens during ionotropic responses?
- involves ions, rapid response
- generally means opening ion channels
what are the effects of a metabotropic response?
- involves metabolism, so its more delayed
- alters cell activity (can cause release of secretory vesicles)
t/f: both rapid and delayed responses are possible after hormone receptor activation
true
receptors for lipophilic hormones are _________
intracellular (cytosol) and/or nuclear
a receptor + its ligand forma a “___________” in lipophilic hormones
DNA-binding protein
what does a DNA-binding protein do?
regulates transcription
- can stimulate or inhibit
what are some non-genomic actions of membrane receptors for steroid hormones?
- open ion channels, leads to an influx of calcium
- this is a much more rapid response than protein synthesis
where is the hypothalamus found?
on the floor of the diencephalon
the pituitary gland lies just below the hypothalamus, in the ___________
sella turcica
t/f: the pituitary gland, along with the hypothalamus, lies within the dura of the brain
FALSE
pituitary gland lies outside the dura
what is the name for the anterior pituitary gland?
adenohyphosis
what is the name for the posterior pituitary?
neurohyphosis
the ________ connects the anterior and posterior pituitary gland
infundibulum
the adenohyphosis is made from an out pocketing of ___________
oral epithelium
Its NOT neural tissue
t/f: the 2 parts of the pituitary differ both in their developmental origin and their connection to the hypothalamus
true
the ________ pituitary is an extension of the hypothalamus, and does not directly synthesize any hormones
posterior
where are the hormones released from the pituitary synthesized?
synthesized in the neuronal cell bodies in the supraoptic and paraventricular nuclei of the hypothalamus
hormones of the posterior pituitary are released in response to what?
action potential
hormones released into capillaries of systemic circulation
what are the hormones of the posterior pituitary?
- oxytocin (acts on smooth mm)
- vasopressin (antidiuretic hormone)
what is the adenohypophysis regulated by?
by hormones secreted by hypothalamic neurons
hypothalamic neurons secrete ________ hormones, which act on the ANTERIOR pituitary. where do the axons of these neurons lie?
hypophysiotropic (or releasing) hormones
axons lie in the median eminence
in the anterior pituitary, there are _____ different cell types that produce _____ primary hormones
5 cell types
6 primary hormones
most hypophysiotropic hormones are named for what?
- named for the anterior pituitary hormone they regulate
- have the suffix “trope”
what are the hormones secreted by the anterior pituitary?
there’s 6 main ones
1) follicle stimulating hormone (FSH)
2) luteinizing hormone (LH)
3) growth hormone (GH)
4) thyroid stimulating hormone (TSH)
5) prolactin (PRL)
6) adrenocorticotropic hormone (ACTH)
____________ is a precursor polypeptide synthesized in corticotrophs
pro-opiomelanocortin (POMC)
what is POMC cleaved to yield?
cleaved to yield multiple peptides with varied actions and target tissues
what does the complexity of the hypothalamus & anterior pituitary system provide?
- multiple control sites
- permits amplification of initial signal
the release of hypophysiotropic hormones is also controlled by other hormones via ____________
feedback mechanisms
long-loop negative feedback is self-regulated by what?
by product/hormone of the ultimate target tissue
short-loop negative feedback occurs when?
when the hormone from the 2nd gland in the axis affects the action of the 1st gland
