During the sports competition a boxer received a strong blow to the abdomen, which caused a knockout due to a brief drop in blood pressure. What physiological mechanisms are the cause of this condition?

Answer options

1. Stimulation of sympathetic nerves
2. Ischemia of the central nervous system
3. Stimulation of parasympathetic nerves
4. Abrupt change in body fluid volume
5. Alteration of transcapillary exchange

Explanation

The vagus nerve (parasympathetic) is the longest cranial nerve. It contains motor and sensory fibers and because it passes through the neck and thorax to the abdomen. The process is called a vasovagal response. You can either stimulate the vague nerve directly by physical contact (punching them in the right place), or by the sheer stress brought on by the pain resulting from the punch. The vagus nerve stimulates the parasympathetic nervous system and inhibits the sympathetic nervous system. This combination can lead to a drastic decrease in heart rate (negative chronotropic), heart contraction (negative inotropy), and/or blood pressure which leads to syncope (fainting).