Answer:
the sympathetic nervous system
Explanation:
The sympathetic nervous system is responsible for the activation of the fight-or-flight response, regulation of the cardiovascular system and the regulation of body temperature, it is part of the autonomic nervous system.
Since the medical equipment company is thinking of developing lie-detection machines that measure perspiration, cardiovascular, and respiration changes which are controlled by the sympathetic nervous system, the should focus on the sympathetic nervous system.