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Flashcards in Receptors, agonists and antagonists Deck (18):
1

Law of mass action

The rate of the reaction is proportional to the concentration of the reactants

2

Hill Langmuir Equation

pAR or y= [A]/ Ka + [A]

3

partial agonists

cannot elicit maximum response ( in the absence of spare receptors)

4

partial agonist at musc receptors

pilocarpine

5

partial agonist at histamine H2 rec

impromidine

6

partial agonists at beta rs

prenalterol, full: adrenaline

7

The EC50 of agonists in tissues vary because of differences in ..

receptor densities and the ability of the receptor to activate the receptor (subtype)= agonist efficacy
and maybe tissue specific factors like the presence of degrading enzymes

8

Ka

measure of affinity : k=1/k-1

9

E

measure of efficacy: forward rate(k+2)/ backward rate(K-2)

10

Antagonists are useful to

block the action of hormones or neurotransmitter, identify receptors and identify enzymes etc involved in signal transduction pathways

11

The antagonist Kb is ..

independent of the nature of the agonist

12

NMDA channel can be blocked by ..

Mg2+ or ketamine

13

Open channel block ..

is a form of non-competitive antagonism, the binding site for antagonist is exposed when the channel opens, has to unblock before it can close

14

Hexamethonium

blocks sympathetic and parasympathetic ganglia. In hexamethonium man:
-Symp effects: reduced sweat and secretions, reduced vasoconstriction (vasodilation) of face, hands , lower legs and feet, impotence.
- Parasymp effects: reduced salivary secretions, loss of accomodation, slight tachycardia, impairment of gut movement

15

Tubocurarine

is a muscle nicotinic ACh Blocker, decreases amplitude of PSP at NMJ, no AP is induced- competitive, non-depolarising neuromuscular blocker

16

Suxamethonium is a depolarising, non-competitive blocker

It activates muscle nicotinic Rs, causes prolonged depolarisation, Na channels are inactivated; depolarising blockers are resistant to acetylcholine esterases ( but not to butyrylcholineesterase or plama esterase, therefore breakdown in 2-6 min)

17

Edrophonium

is a short acting choline esterase inhibitor, makes a reversible ionic bond, used in the treatment of myesthenia gravis

18

Dyflos, an organophosphate,

is an irreversible cholinesterase inhibitor, is used as inseciticide and nerve gas, reactivation with pratidoxime (transfer of phosphate )