lecture 6

Question 1

what does up/down regulation of a hormone mean?

Answer 1

cells adjust their sensitivity to hormone in response to changes in [hormone]

Question 2

Up regulation of a hormone

Answer 2

• trying to maintain response despite low [hormone]
• increased number of receptors in response to sustained low [hormone]

Question 3

Down regulation of a hormone

Answer 3

• decreased number of receptors in response to sustained high [hormone]
• usually involves endocytosis of membrane receptors

Question 4

is up/down regulation short term or long term?

Answer 4

long term effects
take time to occur (endo/exosytosis, protein synthesis)

Question 5

what would be a faster modulation of cell response than up/down regulation?

Answer 5

sensetization and desensitization
- modifying existing receptors (ie. dephosphorylation) to change their activity
- total number of receptors does not change

Question 6

Tropic hormones control

Answer 6

secretion of another hormone

Question 7

give an example of a tropic hormone release cascade

Answer 7

Thyrotropin releasing hormone (TRH) from the hypothlamus
–> causes release of thyrotropin (thyroid stimulating hormone; TSH) from anterior pituitary
–> causes release of thyroid hormones (T3, T4) from thyroid

Question 8

synergism (hormones)

Answer 8

cells/tissues can be under the influence of multiple hormones at any given time
“1+1>2”

there is funtional overlap

reasons not well understood

Question 9

Permissiveness (hormones)

Answer 9

If hormone A can’t produce its full effect without the presence of hormone B, then B is permissive for A

Question 10

Functional antagonists (hormones)

Answer 10

hormones with opposite actions
ex. insulin vs. glucagon and growth hormone

don’t need to share receptors or signalling pathways

Question 11

ligand=

Answer 11

a chemical molecule that binds to a receptor

Question 12

agonist ligand

Answer 12

a ligand that binds to a receptor and enhances the receptor’s activity

Question 13

antagonist ligand

Answer 13

a ligand that binds to a receptor and inhibits the receptor’s activity

Question 14

what is the target cell response determined by?

Answer 14

the receptor and intracellular signalling pathways
NOT on the ligand

Question 15

give an example of how an agonist can have diff effects in diff tissues

Answer 15

adrenaline dilates blood vessels in skeletal muscle but constricts blood vessels in intestines

Question 16

Specificity (of receptors)

Answer 16

receptors may show preference for a particular ligand/type of ligand

Question 17

what would a very specific receptor do?

Answer 17

bind very few ligands

Question 18

what would a non-specific receptor do?

Answer 18

be able to bind many different ligands

Question 19

competition (of receptors)

Answer 19

multiple ligands can compete for the same receptor active site

-the one with the higher affinity/concentration “wins”

Question 20

competitive antagonist

Answer 20

same binding site on receptor as agonist

-can be overcome by increased [agonist]

Question 21

non-competitive antagonist

Answer 21

different binding site on receptor (allosteric site) than agonist

• can’t be overcome by increased [agonist]

Question 22

What is EC(50)?

Answer 22

= [agonist] producing 50% of the max response

Question 23

What does % response depend on?

Answer 23

[agonist] and it increases with % of receptors bound to agonist

• if concentration is high enough, receptors will be saturated and the response it maximal

Question 24

how do competitive antagonists affect agonist binding rate

Answer 24

they make it more difficult for agonist to bind and elicit a response

• max response can still be achieved with high [antagonist]

Question 25

how do non-competitive antagonists affect agonist binding rate?

Answer 25

they change availability of binding site or irreversibly block binding site

-antagonist effect can’t be overcome by increasing [agonist]

Question 26

explain a pathway of release hormones
(Thyrotropin-releasing hormone)

Answer 26

hypothalamic hormone (tropic)= TRH

anterior pituitary hormone (tropic)= TSH, thyroid stimulating hormone

endocrine target= thryoid gland

thryroid gland secreted T3 and T4

Question 27

sensetization is also known as

Answer 27

phosphorylation

Question 28

desensetization is also known as

Answer 28

dephosphorylation

Question 29

what are the 3 insulin pathways?

Answer 29

1. beta cells release insulin
2. stretch receptors detect stretch in stomach
3. glucose sensors in lumen (ex. small intestine) sense lumen glucose and release GLP 1

Question 30

parathyroid hormone (PTH)

Answer 30

PTH is calcium sensing

it goes into circulation and acts on targets if they have a receptor

bone and kidney have calcium