endocrinology lecture 1 Flashcards
(88 cards)
1
Q
what is the route of communication for the endocrine system
A
blood
2
Q
compared to the nervous system, the endocrine system has a _____ onset of response
A
the endocrine system has a DELAYED onset of response
3
Q
compared to the nervous system, the duration of the effects for the endocrine system are
A
the endocrine system’s duration of effects are PROLONGED
4
Q
glands in the e.system are…
A
ductless
5
Q
specificity of tissue response in the e.system is due to what….
A
due to the presence of receptors that are specific to a particular hormone (in that target tissue)
6
Q
if you want to regulate/increase a response to a particular hormone you must (3)
A
- increase secretion of the hormone
- increase the hormone’s availability in the blood
- increase the expression of the hormone’s receptors in the target tissue
7
Q
what are the 3 chemical classes of hormones
A
- peptide/protein
- steroid
- amine
8
Q
peptide hormones are highly variable in ____
A
size! can be just a few a.a to very large proteins
9
Q
what can be added to peptide hormones to make them variable in structure
A
sugar residues…aka they can be glycosylated
10
Q
can peptides fn as both neurotransmitters and hormones?
A
yes! somatostatin and seratonin are examples.
11
Q
what is a preprohormone
A
stage in peptide hormone synthesis. inactive form of hormone that is synthesized on a ribosome. includes extra a.a and foldings.
12
Q
what is a prohormone
A
a stage in peptide hormone synthesis following the preprohormone stage. the preprohormone gets cleaved in the RER to remove the extra a.a. the prohormone is then packaged into vesicles in the Golgi.
13
Q
what is the final stage of peptide hormone synthesis
A
the prohormone is cleaved prior to being in the vesicle OR is cleaved within the vesicle (and when secreted, the hormone is secreted with the fragments)
14
Q
what is the benefit of packaging peptide hormone in vesicles
A
large quantities can be stored for rapid release
15
Q
what is the purpose of precursor molecules in peptide hormone synthesis
A
- prevents intracellular degradation
- limits the feedback effects on the cell
- limits hormone having an effect before it leaves the cell
16
Q
what type of hormones are steroid hormones
A
small lipid hormones
17
Q
what are the sources (which organs secrete) the steroid hormones
A
-gonads
-adrenal cortex
-placenta
these are the primary steroid producing organs
18
Q
all steroids are derived from
A
cholesterol (by a series of rxns)
19
Q
what are the 5 classes of steroid hormones
A
- progestagens
- androgens
- estrogens
- glucocorticoids
- mineralocorticoids
20
Q
what are the progestrogens
A
pregnenolone, progesterone, 17-hydroxyprogesterone
21
Q
what are the androgens
A
dehydroepiandrosterone, androstenedione
22
Q
what are the glucocorticoids
A
corticosterone and cortisol
23
Q
what are the mineralocorticoids
A
aldosterone
24
Q
what are the 2 main sources used for cholesterol synthesis
A
acetyl coA and LDL (made within the cell from these 2 molecules)
25
what is the process by which steroid hormones are made...
1. LDL binds to LDL receptors on the cell and is endocytosed
2. fusion of these vesicles into and endosome
3. w/in the endosome LDL dissociates from the receptor (and the receptor is recycled to surface of cell)
4. LDL delivered to lysosome
5. cholesterol ester is cleaved from the LDL to give free cholesterol
6. this cholesterol is used for membrane synthesis OR is converted to steroid hormones and bile acids
26
how are cholesterol esters stored within steroidogenic cells
w/in lipid droplets in the cell (bc cholesterol is lipid soluble and would otherwise diffuse through the membrane)...this gives the cell a white fatty appearance
27
what initiates steroid hormone synthesis
usually a peptide hormone that binds to a g-protein coupled receptor
28
what is the cascade for steroid hormone synthesis
peptide hormones bind to GPCR-->activate adenyl cyclase-->increase in cAMP-->cAMP activates PKA-->PKA stimulates the activity of cholestrol esterases (which cleave the cholesterol esters from LDL in the lipid droplets)-->free cholesterol is released
29
what is StAR and what is its purpose
StAR=steroid acute regulatory protein. Bc cholesterol is lipid soluble, it is difficult to transport around the "watery" cell. StAR is able to bind to free cholesterol and FACILITATE ITS TRANSPORT TO THE MITOCHONDRIA (crossing both inner and outer membranes)
30
what happens to cholesterol in the mitochondria
it is converted in the mitochondria to steroids
31
that enzymes modify cholesterol in the mitochondria and that do they add/cleave
P450 enzymes. add OH or cleave C-C. the P450 enzymes are located on the inner mitochondrial membrane). **important to note that the type of steroidogenic enzyme present in the cell, determines which steroid is produced from cholesterol (different cells make different steroids)
32
from the mitochondria, where do steroids move to
steroids move from the mitochondria to the SER for further modification and then they DIFFUSE into the blood (across the cell membrane)
33
bc steroids are lipid soluble they cannot be...
stored (or any of the intermediates)
34
what 3 ways is the synthesis of steroids regulated
1. by regulating the peptide hormone that stimulates the synthesis
2. regulating the synthesis of the steroidogenic enzymes
3. the # of the steroidogenic cells
35
what is the pathway for the different classes of steroid hormones
cholesterol--> progestagens--> corticosteroids (glucocorticoids or mineralocorticoids) OR androgens--->androgens to estrogens
36
amine hormones are derived from what
the a.a. tyrosine
37
what are the different amine hormones (4)
1. thyroid hormone
2. norepinephrine
3. epinephrine
4. dopamine
(2,3,&4 are all catecholamines)
38
thyroid hormone is produced where
thryroid gland....duh
39
what are the 2 thyroid hormones
triiodothyronine (T3) and thyroxine (T4)....basically iodinated tyrosine molecules
40
where are the catecholamines synthesized
- norepinephrine and epinephrine--> adrenal medulla
| - dopamine-->hypothalamus
41
T3 and T4 are _____ like with respect to solubility and receptors
steroid like....they are lipophilic and nonpolar (diffuse through the membrane)
42
the catecholamines are _____ like with respect to solubility and receptors
peptide like....they are hydrophilic/polar
43
what are the 2 principles of hormone secretion
1. (most) are secreted in short bursts/bursting pattern....where there is a decrease in hormone [ ] due to clearance/metabolism of the hormone after/between bursts
2. circadian
44
what is the "fourth" class of hormones
eicosanoids
45
what are the eicosanoids derived from
arachidonic acid...aka they are lipids!
46
why are eicosanoids not typically thought of as a class of hormones
bc they are very LOCALLY active and not seen in large amounts in circulation like typical hormones
47
the patterns of hormone secretion can be controlled by what three factors
1. plasma [ ] of a NUTRIENT
2. neural control (like the brain tells an organ when to secrete the hormone)
3. hormonal control (other hormones control hormones release...a cascade)
48
how do hydrophilic hormones travel in the blood vs hydrophobic hormones
hydrophilic hormones are readily transported, but hydrophobic hormones require a carrier protein to be bound to
49
where are carrier proteins (for hydrophobic hormones) synthesized
the liver
50
what affects the availability of hydrophobic hormones
the use of carrier proteins
51
when considering a hydrophobic hormone and its carrier protein, what must happen for the hormone to bind to the receptor
the hormone must be released from the carrier protein...thus the [ ] of the free hormone is a function of the [ ] of the binding protein
52
what is the fn of carrier proteins (2)
1. transport hydrophobic hormones through the blood
| 2. prevent the hydrophobic hormones from degradation and clearance (protects steroid and thyroid hormones)
53
where is the main place for hormone metabolism and excretion
liver and kidneys....they contain enzymes that breakdown/inactivate a hormone (note that degradation can also occur in blood via circulating enzymes)
54
what are the 2 ways that hormones are brokendown/inactivated in the liver and kidneys
1. hydrolysis
| 2. sulfation
55
where are the receptors located for peptide and catecholamine hormones
bc they are hydrophilic...their receptors are on the cell surface in the membrane
56
what are the 2 types of responses for hydrophilic hormones (catecholamines and peptide hormones)
1. ionotropic
| 2. metabotropic
57
what is an ionotropic response
when the hormone binds, an ion channel opens
58
what is a metabotropic response
when a hormone binds, it alters the cell activity (ex. phosphorylation of 2nd messengers)
59
what speed of response is possible with hydrophilic hormones
rapid and delayed....delayed responses occur when a 2nd messenger cascade alters transcription/protein synthesis
60
where are the receptors located for steroid and thyroid hormones
bc they are lipophilic, their receptors are intracellular or nuclear
61
typically, a lipophilic hormone (thyroid or steroid hormone) and its receptor/ligand form a______
DNA binding protein/transcription factor that alters transcription
62
what speed of response is possible with lipophilic hormones
delayed only...bc it alters protein synthesis/transcription. (there are exceptions...see notes)
63
where does the anterior pituitary develop from
outpocketing of oral ectoderm
64
where does the posterior pituitary develop from
buds of the flood of the hypothalamus...remains attached to the median eminence of the hypothalamus via the infindibulum
65
what are the 2 hormones released from the posterior pituitary
1. oxytocin
| 2. vasopressin
66
where are oxytocin and vasopressin synthesized
in the hypothalamus within the:
1. supraoptic
2. paraventricular nuclei
67
what does oxytocin do
stimulates smooth muscle contraction
68
what does vasopressin/antidiuretic hormone do
regulates b.p via the kidney and b.v
69
how is the secretion of the anterior pituitary regulated
by the hypothalamus...the hypothalamus secretes hypophysiotropic/releasing hormones that stimulate the ant. pituitary
70
how do hyophysiotropic hormones travel to the ant. pituitary
at the base of the median eminence of the hypothalamus, portal blood vessels are present (which axons release into)...and from the portal b.v, the hormones travel to the ant. pituitary
71
there are _____ # of different cells in the ant. pituitary that produce ____ different hormones
5 diff cell types producing 6 primary hormones
72
what does GnRH (secreted from the hypothalamus) stimulate the secretion of (from the ant. pituitary)
FSH and LH
73
what does GHRH (secreted from the hypothalamus) stimulate the secretion of (from the ant. pituitary)
Growth hormone
74
what does SS/somatostatin (secreted from the hypothalamus) INHIBIT the secretion of (from the ant. pituitary)
growth hormone
75
what does TRH (secreted from the hypothalamus) stimulate the secretion of (from the ant. pituitary)
TSH
76
what does DA/dopamine (secreted from the hypothalamus) INHIBIT the secretion of (from the ant. pituitary)
prolactin
77
what does CRH (secreted from the hypothalamus) stimulate the secretion of (from the ant. pituitary)
ACTH
78
besides dopamine, what type of hormone are the other 5 releasing hormones from the hypothalamus
small peptide hormones
79
what comprises the 'neuroendocrine system'
hypothalamus, pituitary, target...also called an 'axis'
80
what are the 2 hormones secreted by the ant. pituitary that are products of the proopiomelanocortin gene (POMC)
1. beta-lipotropin
| 2. beta-endorphin
81
what is the long loop feedback mechanism
self-regulation by hormone/product of the ultimate/last target tissue
82
what is the short loop feedback mechanism
hormone from 2nd gland in the axis affects the 1st gland's secretion
83
secretion of hypophysiotropic hormones is controlled by
neural signals
84
what is the target tissue of FSH and LH
gonads...to secrete hormones
85
what is the target tissue of GH
liver/many organs....protein synthesis etc
86
what is the target tissue of TSH
thyroid....secretion of T3 and T4
87
what is the target tissue of prolactin
breasts...development/milk
88
what is the target tissue of ACTH
adrenal cortex...for cortisol secretion
