How do antifungals work in the body?

Antifungals primarily function by targeting the cellular processes of fungi in order to inhibit their growth or reproduction. The correct choice indicates that these medications slow down or hinder the multiplication of fungi. This can occur through various mechanisms, such as disrupting the synthesis of the fungal cell wall or altering the cell membrane's permeability. By doing so, antifungals can effectively prevent the spread of fungal infections within the body, allowing the immune system to eliminate the pathogens more efficiently.

The other options describe actions that are not related to the mechanism of antifungals. For instance, decreasing heart rate is typically associated with certain cardiovascular medications, while blocking nerve impulses in arteries pertains to medications that affect the nervous system or vascular function. Similarly, replacing insulin in diabetic patients relates to treatments for diabetes, which is a completely different area of pharmacology unrelated to antifungal action.