Apharmacology student asks the instructor what an accurate description of a drug agonist is. what is the instructor's best response?

a) a drug that reacts with a receptor site on a cell preventing a reaction with another chemical on a different receptor site
b) a drug that interferes with the enzyme systems that act as catalyst for different chemical reactions
c) a drug that interacts directly with receptor sites to cause the same activity that a natural chemical would cause at that site
d) a drug that reacts with receptor sites to block normal stimulation, producing no effect

A drug that interacts directly with receptor sites to cause the same activity that a natural chemical would cause at that site is the instructors best response.  

Explanation:

Receptors are Macromolecules which involved in chemical signalling within cells. It is possible that receptors are located in the cell surface membrane. Cellular biochemical process is regulated by Activated receptor. The drugs are capable to affect to receptor who is related to the drug’s affinity and also intrinsic efficacy.

The affinity and activity of drug is related to its chemical structure. its effect is decided by the time duration where complex persistence of drug-receptor.  

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.