Pharm. Ch. 4: Pharmacodynamics-Target Tissue Receptors

Question 1

Receptors

Answer 1

-Component on or within a cell that a substance can bind to (usually protein)
-When a drug binds, it initiates a biochemical chain of events

Question 2

Surface Receptors: Ion Channels

Answer 2

Become ion pores that change membrane permeability
-Ex: ACh receptor

Question 3

Surface Receptors: Enzymes

Answer 3

Drugs that bind to receptor site can change enzyme activity of intracellular catalytic component

Question 4

Surface Receptors: G Proteins/Second Messenger

Answer 4

Receptor changes shape, attaches to G protein, protein activates and alters activity of intracellular effector
-Can lead to sustained influence
-Second messenger (substance produced in cell) actually mediates change in function

Question 5

Intracellular receptors

Answer 5

In cytoplasm/nucleus

Question 6

Drug/Receptor interactions depend on

Answer 6

-Drug size/shape compared to receptor binding site
-Electrostatic attraction between drug and receptor

Question 7

Affinity

Answer 7

-Amount of attraction between a drug and receptor
-Relates to the drug amount required to bind to the unoccupied receptors

Question 8

Affinity is influenced by

Answer 8

-local regulators (allosteric modulators that bind to site different from drug)
-Environments (membrane fluidity and organization)

Question 9

Drug selectivity

Answer 9

-Affects only one type of cell or tissue and produces a specific physiological response and fewer side effects that nonselective drug
-Relative term

Question 10

Dose-Response

Answer 10

Proportional to # of receptors occupied by drug (not linear)

Question 11

Agonist

Answer 11

-Can bind and initiate a change (affinity and efficacy)

Question 12

Antagonist

Answer 12

Drug will bind to receptor but will not cause direct change. Can block effect of another chemical

Question 13

Competitive Antagonist

Answer 13

-Vie for same receptor as agonist (equal opportunity)
-whichever drug has higher concentration will have predominant effect
-Agonist can overcome antagonist due to weak bond antagonist forms

Question 14

Noncompetitive Antagonist

Answer 14

-Permanent, irreversible bond
-Terminated only with normal protein turnover, so effect tends to linger

Question 15

Partial Agonist

Answer 15

Occupies all available receptors, but does not evoke max response

Question 16

Mixed agonist-antagonist

Answer 16

Acts as agonist on one tissue, antagonist on another tissue

Question 17

Inverse agonist

Answer 17

Opposite effect of an agonist on cellular function

Question 18

Receptor Desensitization

Answer 18

-Brief, returns to normal within a few minutes after agonist is removed
-Associated with phosphorylation

Question 19

Receptor Internalization

Answer 19

Withdrawn from cell membrane by endocytosis

Question 20

Receptor Down-Regulation

Answer 20

-# of available receptors is diminished (less made or more removed)
-Prolonged

Question 21

Drug Tolerance

Answer 21

-Need to progressively increase dose to achieve therapeutic effects
-May be due to changes in receptor sensitivity and function