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Endocrine > Lecture 2 > Flashcards

Lecture 2 Flashcards

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1
Q

What type of hormones are amines?

What is there half life?

A
  1. Catecholamines: derived from single tyrosine
    2-3 minutes
  2. Indoleamines: derived from single tryptophan
    2-3 minutes
  3. Thyroid hormone (T4/T3): derived from 2 tyrosines
    T4=8 days (very long)
    T3=24 hours
    -behaves more like steroid than amine-bound to binding hormones that protect it from degradation
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2
Q

How long is the half life for peptides/proteins?(most hormones)

A

4-170 minutes

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3
Q

How long is the half life for steroid hormones?

A

minutes to several hours

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4
Q

Catecholamines and Indoleamines
Half life
Travel
Receptor/Activation

A
  1. short half life
  2. travel freely in the blood
  3. membrane receptor–>2nd messenger signaling pathways
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5
Q

What is the main difference between catecholamines and indoleamines?

A

Synthesis
Catecholamines: Tyrosine-Tyrosine Hydroxylase
Indoleamines: Tryptophan-Tryptophan Hydroxylase

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6
Q

What are 3 tyrosine-derived catecholamines? What is the rate limiting step?

A
  1. dopamine
  2. norepinephrine
  3. epinephrine

Tyrosine hydroxylase-rate limiting step
-often used as a marker for dopaminergic activity
(not constitutively active in most cell types)
-when reaction happens you get LDOPA

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7
Q

Where does the formation of epinephrine only happen?

A

Adrenal Medulla

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8
Q

Dopamine acts as both a neurotransmitter and hormone, what 2 main places make dopamine?

A

Brain:

a. substantia nigra (parkinson disease-neurotransmitter)
b. ventral tegmental area(reward pathways, mood, attention)

c. arcuate nucleus(for release to pituitary)
- constitutively active-tonically inhibits prolactin

Adrenal Gland

a. adrenal medulla where it is converted to norepinephrine
- inhibits prolactin release from anterior pituitary

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9
Q

How does dopamine inhibit prolactin?

A

tonic inhibitor of prolactin in the anterior pituitary
1. dopaminergic neurons arise from arcuate nucleus
2. dopamine released into hypophysial capillary bed
(different from other dopaminergic neurons in brain)

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10
Q

What does Norepinephrine function as?
What does it require?
What catalyzes its reaction?
What are tissue concentrations equal to?
Where does conversion from dopamine to norepinephrine mostly take place?

A

Function: hormone and neurotransmitter
Require: requires sympathetic nervous system stimulation
Enzyme: B-hyrdoxylase
Tissue Concentration: equal to that of the synapse-conversion
Place:primarily in neurons

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11
Q

What do sympathetic post-ganglionic neurons release?

A

Norepinephrine

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12
Q

What type of receptors does Norepinephrine act through?

A

Alpha and beta adrenergic receptors

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13
Q

Where does conversion of norepinephrine to epinephrine take place? What nerve innervates this area?

A

adrenal medulla

Splanchnic nerve

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14
Q

What do chromaffin cells of the adrenal medulla do?

A

-homologous to parasympathetic neurons-release hormones into the blood

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15
Q

What are tryptophan-derived indoleamine? What are there rate limiting enzymes?

A

Serotonin-Tryptophan hydroxylase-neurotransmitter and hormone
Melatonin-SNA (N-acetyltransferase) –produced in pineal gland

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16
Q

Where is 95% of serotonin produced and by what? What does it do?

A

enterochromaffin cells in the gut

-vasoconstrictor and stimulates smooth muscle contractions in the intestine

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17
Q

What does serotonin do in the brain?

A

the happiness hormone

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18
Q

What do SSRI’s do?

A

increase the concentration of serotonin at the synaptic cleft by blocking reuptake
ex: prozac
considerations:
-physiological basis of depression not well understood
-desensitization/downregulation of postsynaptic receptors
-Negative feedback-less serotonin produced in presynaptic cells

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19
Q

How are epinephrine and norepinephrine metabolized? What happens when there is too much catecholamine?

A

The same way
-VMA is increased in the urine
comt

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20
Q

What does MAO-monoamine oxidase do?

A

catalyzes oxidative deamination of all monoamines

-MAOA and MAOB both present in humans

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21
Q

What do MAOIs do?

Study These Flashcards
A

used in treatment for depression and other mood disorders – increase dopamine
-ex Nardil-treat depression-now not first choice

22
Q

What does DDC (dopa decarboxylase) do?

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A

decarboxylation conversion of L-Dopa to dopamine

23
Q

What do Carbidopa and Benzerazide do?

Study These Flashcards
A

inhibit DCC

  • inhibits conversion outside cell
  • more Ldopa
24
Q

What does COMT (catechol-0-methyltransferase) do?

Study These Flashcards
A

inactivates and degrades catecholamines

25
What is a comt inhibitor?
Entacapone - inhibits deactivation outside cell - more L-dopa
26
Where melatonin made and what is the rate limiting enzyme? When is this enzyme most active?
pineal gland N-acetyltransferase (SNA) night melatonin is undetectable during the daytime and peaks in the middle of the night
27
What can melatonin be therapeutically used for what is it an inhibitor of?
- jet lag, insomnia, seasonal affective disorder, migrane | - potent inhibitor of reproduction-causes decreased spermatogenesis and testis size in males
28
How does information get from light to the pineal gland to regulate its circadian activity?
light-->RHT-->SCN-->pineal gland | RTH=retinohypothalamic tract
29
Preprohormone
Signal peptide and co-peptide attached
30
Prohromone
Co peptides attached
31
Do hormones and co-peptides get packaged together?
yes
32
What is the half life for hormones made in the hypothalamus vs. the pituitary?
Hypothalamus-small(3-44aa) -1-2min | Pitiuitary-large glycoproteins-20min-3 hours
33
What are steroids derived from?
cholesterol precursor
34
What steroid hormones does the adrenal cortex make?
cortisol, mineralocorticoid, DHEA, adnrostenedione
35
What steroid hormones does the kidney, placenta, testis and ovary make?
kidney: vit D placenta: progesterone, estriol Testis: testosterone Ovary: 17B-estradiol, progesterone
36
What common precursor are all steroid hormones synthesized from?
pregnenolone
37
What transports free cholesterol from the outer mitochondria to the inner mitochondria?
StAR (steroidogenic acute regulatory protein)
38
What happens to the cholesterol transported by StAR in the inner mito membrane?
it is converted to pregnenolone by cytochrome P450side chain cleavage enzyme P450scc (desmolase)
39
What is pregnenolone converted to?
glucocorticoids, mineralocorticoids, androgens, and estrogen
40
What are 4 examples of positive feedback?
Parturition (childbirth) -contractions stimulate oxytocin release from hypothalamus-->more contractions stimulate more oxytocin-birth stops loop Lactation -suckling stimulates release of oxytocin form thalamus-->more suckling more oxytocin-lack of suckling stops loop Ovulation LH stimulates estradiol in developing follicle-estradiol stimulates more LH-release of oocyte stops loop Blood clotting -tissue injury activates platelets--platelets activate more platelets-clotting stops release of signals that activate platelets
41
What does the hypothalamus produce, what does the pituitary produce?
hypothalamus-releasing hormone | pituitary-trophic hormone
42
How does the long loop work?
X inhibits TH or RH or both | -hormone feedback at the level of hypothalamus/pituitary
43
How does the short loop work?
TH inhibits RH | -feedback from pituitary to hypothalamus
44
What is a physiological response-driven negative feedback vs. endocrine axis-driven negative feedback?
physiological-just respond to physiological response no other hormone goes to shut it off Endocrine-hormone goes and shuts it off
45
What does failure at thyroid(primary) look like?
high baseline | -no negative feedback
46
What does does failure at the pituitary(secondary look like?
no response to TRH | undetectable levels of TSH
47
What does failure at the hypothalamus(tertiary) look like?
normal response or protracted return to base line | -receptors down regualted
48
What is euthyroid sick syndrome? (dont need to know)
hypothyroid symptoms with low T4/T3 | normal TSH and thyroid
49
What factors affect circulating hormone levels?
- age - body weight - time of day - male/female - diet
50
BNP has a longer half life than ANP what do they use BNP for?
normal levels can rule out congestive heart failure - higher levels with heart and renal failure - lower levels with obesity - increase with age - higher levels in women

Endocrine (11 decks)

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