2. which of the following will change the equilibrium potential for na+?

1.the gating properties of the na+ channels

2.the concentration of the na+ on the inside of the cell versus the outside

3.the ion channels that are open in the cell

4.the resting membrane potential of the cell

Option C, the ion channels that are open in the cell

Explanation:

Ion channels work on the principle of identification of size of the pore.

The plasma membrane of neuron is slightly permeable to Na+ ion while it is highly permeable to K+ ion. The concentration of Na+ ion is higher outside the cell while it is lower inside the cell while the concentration of K+ ion is higher on the inner side of the cell as compared to the outer side of the cell. The ion gate is responsible for maintain this equilibrium. When sodium potassium pump works (or ion gate is considered open), it causes movement of ions against the gradient through active transportation.  

Hence, option C is correct

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.