Biology Thought Questions, Essay Example

Heroin acts faster on the brain because it can cross through the blood brain barrier faster than morphine due to its highly soluble lipids.  Therefore, heroine results in a faster response in the brain as the drug reaches the cell receptor sites faster.

The threshold is the voltage at which the inward Na+ current equals the outward K+ current.  The membrane voltage would rise above threshold and result in an action potential.  If the threshold is the same as the resting potential, there would be continuous action potential and continuous opening of the Na+ and K+ channels, which in turn would result in desensitization.  In addition, the frequency that the cell would produce action potentials would be zero since the action has been desensitized.

If an action potential moving in an orthodromic direction met and action potential moving in an antidromic direction, nothing would happen due to the refractory period, which is the amount of time a membrane takes to be ready for another stimulus.

A threshold depolarization is necessary for an action potential to occur.  If the membrane channels for potassium are blocked by a drug, the action potential will be blocked or prolonged.