Essential Pharmacology

Question 1

Describe the basic function of receptors

Answer 1

detect a change in the environment (stimulus) and stimulate electrical impulses in response

Question 2

Define what is meant by a receptor

Answer 2

a structure on the surface of a cell (or inside a cell) that selectively receives and binds a specific substance.

Question 3

Define intercellular signalling

Answer 3

chemical signal released from one cell produces a response only in those cells that express the right receptors

different receptors for the same chemical signals can produce a different response in different cells

allows specificity

responses - signal transduction: membrane permeability, metabolism, secretory activity, contractile activity, rate of proliferation or differentiation

Question 4

Define intracellular receptors

Answer 4

some are lipid soluble

can dissolve through lipid bilayer or plasma membrane

bind to intracellular receptor in cytosol or nucleus - nitric oxide binds to soluble guanylyl cyclouse in cytosol, generates cGMP as 2nd messenger that regulates cell activity

steroid hormone - receptors often a transcription factor regulating transcription in nucleus

Question 5

Define the different cell surface receptors

Answer 5

receptor channels - ionotropic receptors eg nicotinic ACh receptors

G protein coupled receptors (GPCRs) - metabotropic receptors, all work via middle man (G protein), massive group

Receptor enzymes - receptors with intrinsic enzyme activity eg. insulin receptors, bound to an enzyme eg, cytokine receptors

integrin receptors - receptors that interact with cytoskeleton

Question 6

Explain the term agonist and antagonist

Answer 6

agonist - mimic normal effect of receptor

antagonist - block normal action of receptor

Question 7

Define affinity and efficacy for a drug receptor

Answer 7

affinity - determined by strength of chemical attraction between drug and receptor

efficacy - determined by how good the drug is at activating the receptor

Question 8

Describe the relationship between agonist concentration and effect

Answer 8

higher concentration of drug creates bigger response

concentration platue due to saturated receptor

Question 9

Define affinity and efficacy

Answer 9

affinity - the degree to which a substance tends to combine with another

efficacy - the ability to produce a desired or intended result

Question 10

Define the source for intracellular calcium

Answer 10

from internal stores via IP3- or Ca2+ - stimulated release Ca from endoplasmic reticulum

from outside the cell via voltage gated or ligand gated Ca ion channels

via inhibition of Ca ion transport out of the cell

Question 11

Define the effects of intracellular calcium

Answer 11

directly effects target protein (eg PKC)

binds to calmodulin which then activates target protein (eg. Ca calmodulin dependent kinase - cam kinase)

works via some other Ca ion binding protein (eg troponin)

Question 12

Explain the therapeutic potential of selective agonists and antagonists

Answer 12

one transmitter may act on several receptor subtypes - adrenaline ( the endogenous agonist activates all adrenoreceptors ,a1, a2, B1, B2 - the master key)

selective agonists are drugs that activate only some of those receptors - eg salbutamol - B2 - agonist

selective antagonist are drugs that block only some of those receptors - eg propanolol - B1,B2 - antagonist