Action of drugs

Question 1

What is a receptor?

Answer 1

Term used to refer to protein molecules found on the cell membrane. In order to cause an effect the drug has to bind to a receptor

Question 2

What is an agonist?

Answer 2

Drugs that fully bind the cell recpetors and in doing so can then cause a specific biochemical effect. Perfect fit for the receptor

Question 3

What is an antagonist?

Answer 3

These drugs reduce or prevent cell receptor activation as they can combine with the receptor but are not an exact fit.
When they combine with the receptor they fail to produce a response. An important point to remember I that they bind they also block the receptor so agonist drugs cannot access the receptor. These drugs are used to prevent the agonist from working or can be used as a reversal agent for some drugs which is desirable to prevent further action of the agonist.

Question 4

What is a non-specific drug?

Answer 4

drugs that bind to a large number of different receptors and in doing so may cause a wider range of effects

Question 5

What is a specific drug?

Answer 5

A drug that binds to a specific receptor or receptors. If the drug has a high affinity it will work on fewer different receptors. This allows the drug to have its desired effect on the specific recpetors without causing adverse effects on others.

Question 6

What does the up-regulation of recptors cause?

Answer 6

Makes animal more sensitive to drugs effects

Question 7

Explain the blood brain barrier

Answer 7

The central nervous system has a range of vital functions and therefore in order to protect its tissue the capillaries in the brain have no gaps in their walls.
Distrubution of drugs to the brain is restricted because the tissue lacks the pores that normally allow rapid movement of small molecules across the membrane. The cells of the brains capillaries are also more tightly joined to each other and are covered with lipid sheaths.
This allows some lipid-soluble drugs to pass across the blood-brain barrier but reduces the ability of water-soluble drugs to diffuse. Essentially lipophilic drugs can more readily pass across the blood brain barrier so they are distrubted more effectively to the CNS