Endocrine Principles (Lec 15) Flashcards
_____ feedback prevents over-activity of hormone systems
negative
In regards to feedback loops, controlled variable is sometimes not the ___ rate of the hormone itself but the degree of ___ of the target tissue
secretory; activity
LH surge is an example of ___ feedback
positve
Describe the sequence of events during the LH surge
prior to ovulation, estrogen stimulates the surge of LH; LH acts on ovaries to secrete more estrogen; secreted estrogen stimulates the release of more LH; additional LH results in typical negative feedback
In regards to feedback loops, seasonal changes and various stages in development and aging are examples of what?
how periodic variations in hormone release are superimposed on the negative and positive feedback mechanisms
What are the locations of receptors?
in or on the surface of cell membrane; in the cell cytoplasm; in the cell nucleus
In regards to down regulation of receptors, the number of active receptors may decrease because of increased ___ concentration and increased ___ to receptors
hormone; binding
Down regulation of receptors may occur as a result of inactivation of what type of molecules?
intracellular protein signaling molecules; receptor molecules
Down regulation of receptors may occur as a result of temporary ______ of the receptor inside the cell
sequestration
Down regulation of receptors may occur as a result of destruction of the receptors by ____ after they are internalized
lysosomes
Down regulation of receptors may occur as a result of decreased production of ____
receptors
____ regulation decreases the target tissue’s responsiveness to the hormones
down
In regards to up regulation of receptors, the number of active receptors or intracellular signaling molecules may ____
increase
Up regulation of receptors may occur as a result of the ____ hormone may induce greater than normal
stimulating
Up regulation of receptors may occur as a result of the stimulating hormone may induce greater ___ of the receptor for interaction with the ____
availability; hormone
What type of receptors are used primarily by NTs?
Ion-channel-linked receptors
What do G protein-linked hormone receptors couple with?
groups of cell membrane proteins called heterotrimeric GTP-binding proteins
How many transmembrane segments are in G-protein-linked hormone receptors?
7
True or false?
All G proteins are stimulatory
False; some are inhibitory, some are stimulatory
The following characteristics describe what type of receptor:
single-pass transmembrane receptors;
receptor part is extracellular;
intracellular enzyme may be part of the receptor or separate
enzyme-linked hormone receptor
The leptin receptor (JAK-STAT) is an example of what type of receptor?
enzyme-linked hormone receptor
Adrenal and steroidal hormones, thyroid hormone, retenoid hormones, and vitamin D are associated with what type of receptor?
intracellular receptor
Where does the activated hormone-receptor complex bind?
to promoter sequence of DNA
True or false?
polypeptide < 100 AA
protein > 100 AA
true
Where are polypeptide and protein hormones stored?
secretory vesicles until needed
Polypeptide and protein hormones are usually synthesized as what?
preprohormones
How are polypeptide and protein hormones released?
exocytosis mediated via calcium ions; release for some may involve cAMP
Steroids are usually synthesized from what?
cholesterol
Steroids are ___ soluble and diffuse readily across cell membranes
lipid
Steroids consist of ___ cyclohexyl ring(s) and ___ cyclopentyl ring(s)
3; 1
Cortisol, aldosterone, testosterone, and estradiol are all what type of hormone?
steroid
What type of hormones are derived from tyrosine?
amine hormones
Amine hormones include ___ and ___ ___ hormones
thyroid; adrenal medullary
Amine hormones are formed by actions of enzymes in ___ compartments of ___ cells
cytoplasmic; glandular
Thyroid hormones are incorporated into macromolecules of ___ and stored in thyroid gland ___
thyroglobulin; follicles
Catecholamines are formed in ___ ___ and stored in vesicles until needed
adrenal medulla
In regards to the adenyl cyclase-cAMP second messenger system, binding of hormones with a receptor allows coupling of the receptor to what?
a G protein
cAMP activates what?
cAMP-dependent kinase
Gi proteins ___ the formation of ATP
reduce
In this system, hormones activate transmembrane receptors that activate enzyme PLP C
cell membrane phospholipid second messenger system
PLP C catalyzes breakdown of what?
phospholipids in the cell membrane: PIP2 -> IP3 and DAG
IP3 mobilizes ___ ions from mitochondria and ER
calcium
DAG activates what?
protein kinase C
In the calcium-calmodulin phospholipid second messenger system, how is calcium entry initiated?
by changes in membrane potential that open calcium channels; a hormone interacting with membrane receptors that open calcium channels
What happens when 3-4 binding sites (for calcium) on calmodulin are filled?
activation of protein kinases; inhibition of protein kinases
Which hormones act directly on DNA?
steroids, and thyroid hormones
Once in the nucleus, what do thyroid hormones influence?
transcription of proteins that enhance metabolic activity
True or false?
once bound to DNA, thyroid hormones remain bound for days to weeks and continue to function
true
The following cell types are found where:
Samatotropes (HGF), Corticotropes (ACTH), Thyrotropes (TSH), Gonadotropes (LH and FSH), Lactotropes (Prolactin)
Anterior Pituitary (AP)
In regards to the posterior pituitary, magnocellular neurons are located in the ___ and ___ nuclei
supraoptic; paraventricular
__ is formed primarily in the supraoptic nuclei
ADH
___ is formed primarily in the paraventricular nuclei
oxytocin
The hypothalamus controls AP via hormones called what?
hypothalamic releasing and inhibitory hormones
How are hypothalamic releasing and inhibitory hormones conducted to AP?
via hypothalamic-hypophyseal portal system
Where are hypothalamic releasing and inhibitory hormones secreted?
into median eminence
Where do hypothalamic releasing and inhibitory hormones diffuse?
into portal system
The hypothalamus is a collecting center for information concerning what?
internal well-being of body
Growth hormones increase deposition of protein by ___ and ___ cells
chondrocytic; osteogenic
Growth hormone converts ____ into osteogenic cells
chondrocytes
Growth hormone strongly ____ osteoblasts
stimulates
In regards to protein synthesis, growth hormone directly enhances transport of ___ ___ through cell membranes into cytoplasm
amino acids
In regards to protein synthesis, growth hormone increases RNA translation and transcription rate while decreasing protein ___
catabolism
In regards to FA mobilization, growth hormone causes release of FAs from ___ tissue
adipose
In regards to FA mobilization, growth hormone enhances conversion of FAs to what?
acetyl-CoA
In regards to decreasing glucose utilization, growth hormone decreases ___ uptake in tissues such as ___ muscle and fat
glucose; skeletal
In regards to decreasing glucose utilization, growth hormone increases ____ production by liver
glucose
In regards to decreasing glucose utilization, growth hormone increases ___ secretion
insulin
True or false?
Growth hormone’s effects are diabetogenic
true
In regards to causing liver to form somatomedins (proteins), growth hormone has powerful effect on all aspecs of ____ growth
bone
In regards to causing liver to form somatomedins (proteins), effects of growth hormone are similar to ___ on growth
insulin
What is the most important growth factor?
somatomedin C (IGF-I)
Injection into ___ ___ causes specific growth of these regions
epiphyseal plates
Starvation, hypoglycemia, exercise, excitement, trauma, ghrelin, first two hours of deep sleep are all factors known to stimulate secretion of what?
growth hormone
Metabolic clearance rate = ?
rate of disappearance of hormone from plasma/concentration of hormone
