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Veterinary Physiology > Mechanism of Hormone Action & Second Messengers > Flashcards

Mechanism of Hormone Action & Second Messengers Flashcards

1
Q

What is the final outcome interaction of hormone and target cells? It depends on several factors…

A

hormone concentration
receptor number
affinity of hormone for receptor
duration of exposure to hormone
intracellular factors

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2
Q

What is the threshold response?

A

minimal concentration of hormone needed to elicit a measurable response
- dose-response curve

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3
Q

What is this curve called?

A

dose-response curve

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4
Q

Responsiveness is expressed in a _______ relationship

A

dose-response

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5
Q

The magnitude of the response correlated with _________

A

hormone concentration

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6
Q

As hormone concentration increases, response [increases/decreases] then levels off

A

increases

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7
Q

More receptors = [more/less] maximal response

A

more

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8
Q

Higher affinity for hormone = [more/less] likely to get a response

A

more

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9
Q

What is maximum response

A

a further increase in hormone will elicit no more response

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10
Q

Define sensitivity

A

the concentration of hormone producing 50% of maximal response

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11
Q

If more hormone is required to get 50% response, sensitivity [increases, decreases]

A

decreases

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12
Q

In what two ways can sensitivity be changed?

A

change number of receptors
affinity of receptors

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13
Q

What does down-regulating mean?

A

decreasing sensitivity
either the number or affinity of receptors decreases even when hormone concentrations are high*

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14
Q

In down-regulation, there is a(n) [increase/decrease] of new receptors, and a(n) [increase/decrease] in degradation of existing receptors leading to [activation/inactivation] of receptors

A

decrease
increase
inactivation

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15
Q

What is an example of down-regulation?

A

T3 down-regulates TRH receptors in anterior pituitary

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16
Q

What does up-regulating mean?

A

increasing sensitivity
either the number or affinity of receptors increase

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17
Q

In up-regulation, there is a(n) [increase/decrease] of new receptors, and a(n) [increase/decrease] in degradation of existing receptors leading to [activation/inactivation] of receptors

A

increase
decrease
activation

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18
Q

What is an example of up-regulation?

A

GH increases its receptors in skeletal muscle and liver

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19
Q

What is the general mechanism of hormone action?

A

hormone recognized and binds to membrane receptor
hormone receptor complex either coupled to signal-generating mechanism OR acts as one itself
generated signal (2nd messenger)

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20
Q

When the hormone is recognized and binds to a membrane receptor, it forms a _______ complex

A

hormone-receptor complex

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21
Q

Hormone-receptor complexes are what two forms?

A

coupled to a signal-generating mechanism
OR
acts as a signal-generating mechanism itself

22
Q

The generated signal (2nd messenger) affects intracellular process in what two ways?

A

alter activity
OR
alter concentration of functional/structural proteins

23
Q

Where are receptor systems?

A

cell membrane or within cell

24
Q

What are the types of hormone receptor systems?

A

classic cell membrane systems
catalytic cell membrane receptor systems
intracellular receptor systems

25
Q

How are classic cell membrane receptor systems classified?

A

classified according to membrane receptor structure
OR
second messenger system used
- rapid response

26
Q

Do catalytic cell membrane receptor systems use a second messenger system? If not, what do they use?

A

NO
enzyme system such as kinases
- usually a rapid response

27
Q

What do intracellular receptor systems use?

A

cytoplasmic or nuclear receptors
- SLOW

28
Q

T/F: G-proteins are coupling molecules use in almost all membrane receptor systems

A

TRUE

29
Q

What are G-proteins composed of?

A

heterotrimeric proteins (3 subunits)

30
Q

G-proteins are [activated/inactivated] when GTP is bound, [active/inactive] when GDP is bound

A

active
inactive

31
Q

G-proteins can be ______ & _______

A

stimulatory
inhibitory

32
Q

G-proteins are linked to one of two second messenger systems. What are they?

A

adenylyl cyclase w/ cAMP
phospholipase C w/ IP3/Ca2+

33
Q

Adenylyl cyclase (enzyme) is linked with which second messenger?

A

cAMP

34
Q

Phospholipase C (enzyme) is linked with which second messenger?

A

IP3/Ca2+

35
Q

In the adenylyl cyclase system, GTP binds G protein and activates _____. The 2nd messenger, ______, is produced and activates ________. Intracellular proteins are phosphorylated by __________, causing physiologic actions

A

adenylyl cyclase
cAMP
protein kinase A
protein kinase A

36
Q

In the phospholipase C system, GTP binds G protein and activates ______ which liberates _________ and _________ from ________. The second messenger, ______ causes [Na+/Ca2+/K+] release from ER or SR stores. _________ and ___________ activates __________, which phosphorylates proteins

A

phospholipase C
DAG and IP3
IP2
IP3
Ca2+
Ca2+ and DAG
protein kinase C

37
Q

What uses the catalytic receptor system?

A

ANP (anthill natriuretic peptide)
NO

38
Q

What is the catalytic receptor system?

A

catalytic receptors on cell surface associated with enzymes on intracellular side

39
Q

What enzymes are part of the catalytic receptor systems?

A

guanylyl cyclase enzyme
serine/threonine kinase enzymes
receptor tyrosine kinases

40
Q

Define receptor tyrosine kinases

A

tyrosine kinase activity WITHIN the receptor itself
has 3 domains
when hormone binds, intracellular portion of receptor phosphorylates itself
monomer and dimer types

41
Q

What does then extracellular domain of receptor tyrosine kinases do?

A

binds hormone

42
Q

What does then intracellular domain of receptor tyrosine kinases do?

A

where tyrosine kinase activity occurs

43
Q

What are the 3 domains of receptor tyrosine kinases?

A

extracellular domain
transmembrane domain
intracellular domain

44
Q

What is the monomer type of receptor tyrosine kinases?

A

receptor is going to dimerize AFTER hormone binds
- tyrosine kinase is activated and phosphorylates tyrosine on itself

45
Q

What is the dimer type of receptor tyrosine kinases? Give two examples

A

receptor is already a dimer
- insulin & IGF (insulin-like growth-factor 1)

46
Q

What are tyrosine kinase-associated receptors?

A

associate with other proteins that have tyrosine kinase activity - Janus kinase family

47
Q

T/F: The intracellular portion of tyrosine kinase-associated receptors cannot phosphorylate itself

A

TRUE

48
Q

Steroid hormones use _________ systems and use either _______ or _________

A

intracellular receptor
cytosolic OR nuclear receptors

49
Q

Steroids initiate DNA [transcription/translation] and synthesis of new proteins

A

transcroption

50
Q

Steroid hormones diffuse across the membrane and binds receptor in _____ or _______

A

cytosol
nucleus

51
Q

What are steroid-responsive elements?

A

specific DNA sequences in target genes
once the steroid diffuses and binds to a receptor, the receptor undergoes a conformational change. The complex binds to these steroid-responsive elements

52
Q

After the complex binding to the steroid-responsive elements, the complex is now a ______ factor, and _____ is transcribed, translation occurs, new proteins, physiologic actions

A

transcription
mRNA

Veterinary Physiology (26 decks)

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