Endocrine Physiology Flashcards
1
Q
What is another name for somatostatin?
A
Growth hormone inhibiting hormone
2
Q
what is another name for prolactin inhibition factor?
A
dopamine
3
Q
what hormones are released from the hypothalamus?
A
TRH
CRH
GhRH
GhIH (somatostatin)
GRH
PIF (dopamine)
4
Q
what hormones are released from the anterior pituitary?
A
GH
TSH
prolactin
adrenocorticotropic hormone
FSH
LH
5
Q
what hormones are released from the posterior pituitary?
A
ADH (vasopressin)
oxytocin
6
Q
what hormones are released from the thyroid?
A
T3
T4
calcitonin
7
Q
what hormones are released from the adrenal cortex?
A
cortisol
aldosterone
8
Q
what hormones are released from the adrenal medulla?
A
epi/norepi
9
Q
what endocrine hormones are released from the pancreas?
A
insulin
glucagon
10
Q
composition of hormones in the body
A
polypeptides (<100 AA)
proteins (>100 AA)
11
Q
where in the cell are most hormones synthesized? what is the process of hormones being stored and released?
A
synthesized on rough ER > prohormones (inactive) transferred to Golgi to be packaged in secretory vesicle
inc cytosolic Ca conc (from PM depolarization) > exocytosis
OR
(secondary messenger system)
stimulation of cell surface receptors > inc cAMP > activates protein kinases > initiaties hormone secretion
12
Q
explain the following for steroid hormones: synthesis, storage, solubility, binding
A
synthesized from cholesterol
not stored
lipid soluble
13
Q
explain the following for amine hormones: synthesis, storage, solubility, binding
A
derived from tyrosine
thyroid + adrenal medullary hormones
thyroglobulin incorporates thyroid hormones in thyroid gland
thyroxine binding globulin binds in plasma
14
Q
how are hormones cleared from plasma?
A
metabolic destruction by tissues
binding by tissues
excretion by liver > bile
excretion by kidneys > urine
15
Q
what is the metabolic clearance rate?
A
rate of removal of hormone from blood (mL/min)
rate of disappearance of hormone from plasma / conc of hormone
16
Q
what types of hormone receptors are in or on the surface of the cell membrane?
A
protein, peptide, catecholamine hormones
17
Q
what types of hormone receptors are in the cell cytoplasm?
A
steroid hormones
(they’re lipid based so can get into the cell)
18
Q
what types of hormone receptors are in the cell nucleus?
A
thyroid hormones
19
Q
how are hormone receptors down-regulated? what does this mean about their function change/how fast it occurs?
A
receptor proteins are inactivated/destroyed DURING their function and thus can change from day to day or minute to minute
20
Q
what are some scenarios that would result in down regulation of hormone receptors?
A
inactivation of receptor molecules
inactivation of intracellular protein signalling molecules (GMP, cAMP, etc)
temporary seqeuestration of receptor to inside of cell (away from site of action of hormones that interact w it)
destruction of receptors by lysosomes after they’re interalized
dec production of receptors
21
Q
what are the two most common types of hormone receptor complexes?
A
ion channel linked receptor
G protein linked receptors*
enzyme linked receptors
IC hormone receptors
22
Q
describe an ion channel linked hormone receptor complex
A
all NT substances combine w receptors in postsynaptic membrane
>
change in structure of receptor (opening/closing ion channel; Na, K, Ca, etc)
23
Q
describe a G protein linked hormone receptor complex
A
activates receptors that indirectly regulate activity of target proteins by coupling with groups of cell membrane proteins (GTP (G) binding proteins)
> Heterotrimeric guanosine triphosphate
>7 transmembrane segments
inhibitory and stimulating G proteins
24
Q
describe an enzyme linked hormone receptor complex
A
proteins that pass through the membrane only once
hormone binding site EC and catalytic/enzyme binding site IC
ex: tyrosine kinase > leptin receptor
25
describe an IC hormone receptor complex
activation of genes
adrenal and gondal steroid hormones, thyroid hormones, vit D, retinoid hormones; bind with protein receptors within cell (lipid soluble, pass thru plasma membrane)
activated complex binds with regulatory (promotor) sequence of DNA (hormone response element) > activation/repression of transcription of genes and mRNA
26
briefly describe the adenylyl cyclase-cAMP second messenger system
hormone (1st messenger) binds receptor EC> coupling of receptor to a G protein IC
g protein activates (or inhibits), effector enzyme adenylyl cylase (membrane bound enzyme) > converts ATP to cAMP (2nd messenger) inside the cell
activates cAMP dependent protein kinase > phosphorylates other proteins
enzyme cascade is activated
small amount of hormone = large effect
27
briefly describe the phospholipase C second messenger system
enzyme catalyzes breakdown of phospholipids in cell membrane
hormone activated G protein activated an effector enzyme (phospholipase C) which then splits membrane protein PIP2 into two second messengers:
- inositol triphosphate (IP3) > releases Ca ions from mitochondria and ER
- diacylglycerol (DAG) > activates enzyme protein kinase C
28
briefly describe the thyroid hormone hormone receptor system
T3 and T4 directly bind to receptor proteins in nucleus
> control function of gene promoters
> activate genetic mechanisms for synthesizing many types of IC proteins
(receptors = activated TFs within chromosomal complex)
29
what are some differences between the endocrine and nervous systems?
nervous:
- fast response (directly into blood)
- short duration
- act via AP and NTs
- Act over very short distances
- act at specific locations determined by axon pathways
endocrine:
- slow response (2nd messenger systems)
- longer duration
- act via hormones
- act over long distances
- diffuse target locations
30
what is the difference between exocrine and endocrine glands?
exocrine glands
- produce nonhormonal substances (sweat, saliva)
- have ducts to carry secretion to membrane surface
endocrine glands
- produce hormones, lack ducts
31
what organs have exocrine AND endocrine functions?
pancreas, gonads, placenta
32
what other tissues/organs produce hormones besides endocrine glands?
adipose cells
thymus
cells in small intestine, stomach, kidneys, heart
33
what glands are endocrine glands?
pituitary
thyroid
parathyroid
adrenal
pineal
*hypothalamus is NEUROendocrine gland
34
autocrines vs paracrines vs hormones
hormones: long distance chemical signals that travel in blood or lymph
autocrines and paracrines are local messengers; not part of endocrine system
autocrines: chemicals that exert effects on same cells that secrete them
paracrines: locally acting chemicals that affect cells other than those that secrete them
35
main classes of hormones
amino acid based: AA derivatives, peptides, proteins
steroids (from cholesterol): gonadal and adrenocortical hormones
36
hormone action on target cells may be done in order to:
alter PM permeability and/or MP by opening/closing ion channels
stimulate synthesis of enzymes or other proteins
activate/deactivate enzymes
induce secretory activity
stimulate mitosis
37
what are the types of hormone actions and what determines them?
determined by chemical nature and receptor location
water-soluble hormones (all AA based hormones except for thyroid hormone):
-act on PM receptors
-act via G protein 2nd messengers
-cannot enter cell
lipid soluble hormones (steroid and thyroid hormones):
- act on IC receptors that directly activate genes
- can enter cell
38
what are the types of endocrine gland stimuli?
humoral - changing blood levels of ions and nutrients directly stimulate hormone secretion
neural - nerve fibers stim hormone release
hormonal - hormones stim other endocrine organs to release their hormones
39
what connects the hypothalamus and pituitary gland?
infundibulum (a stalk)
40
what is the hypophysis? neurohypophysis? adenohypophysis?
hypophysis - pituitary gland
neurohypophysis - posterior lobe + infundibulum
adenohypophysis - anterior lobe
41
differences between the lobes of the pituitary gland
posterior: composed of neural tissue from a downgrowth of brains > secretes neurohormones
anterior: glandular tissue
42
explain the neural connections and hormones released by the posterior pituitary
post pituitary has neural connection to hypothalamus via hypothalmic-hypophyseal tract (arises from neurons in paraventricular and supraoptic nuclei); runs through infundibulum
secretes oxytocin and ADH (stored in axon teerminals and released in blood when neurons fire)
43
oxytocin actions
stimulates uterine contractions during childbirth
hormonal trigger for milk ejection
^ both pos feedback mechanisms
NT in brain (uses PIP Ca 2nd messenger system)
44
ADH (antidiuretic hormone) actions
targets kidney tubules to reabsorb more water or inhibit/prevent urine formation
high concentrations cause vasoconstriction (hence other name of vasopressin)
45
how is the release of ADH stimulated/inhibited?
hypothalamus contains osmoreceptors that monitor solute concentrations
if conc too high > post pit secretes ADH
release also triggered by pain, low BP, drugs
inhibited by alcohol, diuretics
46
describe the derivation of the anterior lobe of the pituitary as well as its connection to the hypothlamus
ant lobe derived from an outpocketing of oral mucosa
vascularly connected to hypothalamus via hypophyseal portal system (primary capillary plexus, hypophyseal portal veins, secondary capillary plexus)
hypothalamus secretes releasing and inhibiting hormones to anterior pituitary to regulate hormone secretion
47
anterior hormone hormones
all 6 are peptide hormones
all but GH activate target cells via cAMP 2nd messenger sys
all but two are tropic hormones/tropins (besidesGH and PRL) that regulate secretion of other hormones
GH
TSH
ACTH
FSH
LH
PRL
48
GH production and actions
also called somatotropin as it is produced by somatotropic cells
direct actions on metabolism
indirect actions on growth
49
GH actions on metabolism
DIRECT actions on metabolism
- glucose sparing: dec rate of cellular glucose uptake and metabolism (anti insulin)
- triggers liver to breakdown glycogen > glucose
- inc blood levels of FAs for use as fuel, encourages cellular protein synthesis
50
GH actions on growth
INDIRECT actions on growth
- triggers liver, skeletal muscle, and bone to produce insulin like GFs (IGFs)
- IGFs stimulate:
1. cellular uptake of nutrients to synthesize DNA and proteins needed for cell divison
2. formation of collagen and deposition of bone matrix
-GH stim most cells to enlarge and dividie, but major targets are bone and skeletal muscle
51
TSH hormone type, release, inhibition, action
tropic hormone also called thyrotropin as it is produced by thyrotropic cells
stimulates normal development and secretory activity of thyroid
release triggered by TRH from hypothalamus
inhibited by rising blood levels of thyroid hormones that act on both pituitary and hypothalamus - also inhibited by GHIH
52
ACTH hormone type, release, inhibition, action
corticotropin; secreted by corticotropic cells
stimualtes adrenal cortex to release corticosteroids
release is triggered by hypothalmic CRH in daily rhythm (highest in morning)
release also affected by fever, hypoglycemia, and stressors
53
whats a precursor to corticotropin?
pro-opiomelanocortin
54
what cells secrete FSH/LH?
gonadotropic cells of anterior pituitary (they are also called gonadotropins)
55
FSH and LH actions
FSH stim production of gametes (eggs/sperm)
LH promotes production of gonadal hormones (in females = matures egg follicles, triggers ovulation and release of estrogen/progesteorne, males stimulates testosterone production)
56
regulation of LH/FSH release
triggered by GnRH during/after puberty (LH/FSH not present in prepubertal blood)
suppressed by gonadal hormones (feedback)
57
prolactin secretion, action, and regulation
secreted by prolactin cells of anterior pituitary
stim milk production
regulation primarily controlled by PIH/dopamine; prevents release of PRL until needed
inc estrogen levels and suckling can also stimualte PRL
58
is iodine transfer from blood to cell for thyroid hormone synthesis passive or active?
active
59
composition of units T3 and T4
T4 = DIT + DIT
T3 = DIT + MIT
60
explain the formation of thyroglobulin
ER + golgi > thyroglobulin (70 tyrosine AA)
T4/T3 formed from tyrosine in thyroglobulin molecule remain part of molecule during synthesis of thyroid hormones and after in follicular colloid
61
explain thyroid hormone formation
iodine converted via oxidation with peroxidase and hydrogen peroxide
iodine binds with thyroglobulin molecule (organification)
storage within thyroid gland; can store 2-3 months of hormone
62
explain the iodide pump
sodium iodide symporter (iodide trapping)
transports iodides from blood > thyroid cells/follicles where the basal membrane of thyroid pumps iodide into the cell
symporter cotransports 1 iodide ion and 2 sodium ions
energy from Na/K ATPase pump > pumps Na out of cell giving low IC Na and a gradient for facilitated Na diffusion into cell
63
where is iodide located in the thyroid gland?
cytoplasm of follicular cells
64
thyroid peroxidase functions
oxidation
organification of iodine
coupling of MIT and DIT
65
explain the conversion of T4 > T3 in peripheral tissue
follicles of thyroid 5-deiodinase converts T4>T3 in peripheral tissue
peripheral conversion inhibited by glucocorticoids, beta blockers, propylthiouracil (PTU)
reverse T3 = metabolically inactive byproduct of peripheral conversion of T4 and its production is increasd by GH and glucocorticoids
66
how is T4/T3 released from the thyroid gland?
cleaved from thyroglobulin molecule > free hormones released
pinocytic vesicles enter thyroid cell > lysosomes fuse with vesicles > proteases digest thyroglobulin and release T4/T3 > diffuse through base of thyroid cell to capillaries
67
explain the transport of T4/T3 to tissues
once in blood, bound to plasma proteins (synthesized in liver) > thyroxine binding globulin
released slowly to tissue cells > bind with IC proteins and stored or used
slow onset and long duration of action (max rate after 10-12 days)
68
T3 functions
7 Bs
Brain maturation
Bone growth (synergistic w GH)
B adrenergic effects (inc B1 receptors in heart > inc CO, HR, SV, contractility)
BMR (via inc Na/K ATPase > inc O2 consumption, RR, body temp)
Blood sugar (through glycogenolysis and gluconeogenesis)
Break down lipids (through lipolysis)
Babies (stim surfactant synthesis)
69
effect of thyroid functions
increase transcription of genes
inc cellular metabolic activity
effects on growth
effects on certain body functions
70
what is the role of the thyroid in transcription?
most t4 > t3 prior to acting on genes to inc genetic trasncription
thyroid hormone receptors are attached to DNA genetic strands OR located in proximity to them
thyroid hormone receptor forms a heterodimer with retinoid X receptor (RXR) at specific parts of DNA
71
what thyroid hormone is more active? why?
T3; IC thyroid receptors have a higher affinity for T3 and it more readily binds
72
how do thyroid hormones increase cellular metabolic activity?
inc mitochondira size, number, and activity
- inc membrane SA
- inc ATP production
inc active transport of ions through cell membranes
- Na/K ATPase enzyme inc
- inc rate of transport of Na and K through cell membranes
- inc body heat
- cell membrane = leaky to Na ions
73
thyroid metabolic actions
stimulates carb and fat metabolism
inc BMR
dec body weight
inc blood flow and cardiac output
inc vitamin requirement
effect on plasma and liver fats
74
how does thyroid hormone stimulate carb metabolism
rapid glucose uptake by cells
inc glycolysis
inc insulin secretion
75
how does thyroid hormone stimulate fat metabolism
lipids mobilized rapidly from fat tissue, dec fat stores in body
76
thyroid hormone effect on plasma and liver fats
inc thyroid hormone = dec conc of cholesterol, phospholipids, and TGs, but INC free FAs
77
how does thyroid hormone lead to an increased vitamin requirement?
inc quantities of body enzymes; vitamins are a part of/cofactors for many of these enzymes
too much thyroid = vitamin def
78
how does thyroid hormone inc CO?
inc tissue metabolism > inc oxygen use > vasodilation > inc blood flow > inc CO
79
functions of TSH
inc proteolysis of thyroglobulin
inc activity of iodide pump
inc iodination of tyrosine
inc size, secretory activity, and number of thyroid cells
80
describe the thyroid hormonal pathway
TRH (hypothalamus) > TSH (ant pit) > T3/T4 (follicular cells)
81
how do t3/t4 become inactive?
being bound; usually by thyroxine-binding globulin (TBG)
82
what secondary messenger system is used in TSH regulation
Cyclic adenosine monophosphate (cAMP)
83
how does TRH regulate the secretion of TRH?
TRH binds with receptors on pituitary cell membrane > activates phospholipase 2nd messenger system >
large amts phospholipase C produced > 2nd messengers including Ca > release of TSH
84
how does cold exposure affect TRH?
cold exposure inc TRH (excitation of hypothalmic centers for body temp control)
inc TSH > BMR 15-20% higher
85
how does leptin input affect TRH?
TRH neurons in PVN receive input from leptin neurons in arcuate nucleus that regulate energy balance
prolonged fasting dec plasma leptin > dec POMC activity > INC NPY/AGRP neuronal activity
dec leptin > indirectly inhibits TRH > dec thyroid hormone secretion
86
how do things like excitement/anxiety affect TSH secretion?
excitement/anxiety stim SNS > dec in TSH secretion
87
what is the wolff-chaikoff effect
protective autoregulation
sudden exposure to excess iodine (chemoreceptors notice) > temp turns OFF thyroid peroxidase > dec t3/t4 production
(why ppl take iodine when around radiation to avoid it coming into the thyroid)
88
what is most commonly supplemented in hypothyroidism?
T4, unless body has conversion issue from T4>T3
both can be used
89
what happens in graves dz?
ab produced that stim TSH receptors and keep producing thyroid hormone with low TSH still; "mimicry of TSH"
90
hormones that directly activate genes are classified as
lipid soluble
91
oxytocin is produced where
hypothalamus (then stored in post pituitary)
92
in what region of the adrenal gland is aldosterone produced?
adrenal cortex (zona glomerulosa)
93
hormones are secreted in response to what types of stimuli
neuronal
humoral
hormonal
NOT up regulation > that just increases receptors
94
the ant pituitary stimulates other endocrine organs by secreting a group of hormoness called
tropic hormones - target other endocrine organs
95
which endocrine gland is tiny, yellow-brown and arranged in thick, branching cords?
parathyroid gland
96
what are the effects of PTH?
inc osteoclast activity
inc ca reabsorption in kidney
inc ca absorption in intestine
97
most of the AA based hormones affect the target organs using
intracellular second messengers (theyre too big and non lipid based, cant go directly into cell)
98
a person with endemic goiter suffers from
hypofunctioning thyroid gland (iodine def)
99
