Final answer:
The sympathetic division of the autonomic nervous system prepares the body for vigorous activity by triggering the fight-or-flight response, which includes increased heart rate and other physiological changes.
Step-by-step explanation:
The component of the autonomic nervous system responsible for preparing the body for vigorous activity is the sympathetic division. During situations perceived as emergencies or during vigorous activities such as exercise, the sympathetic division triggers what is known as the fight-or-flight response. This physiological reaction includes an increase in heart rate, activation of sweat glands, dilation of the bronchi in the lungs, dilation of pupils, and a rise in blood pressure. These changes optimize the body's ability to respond quickly and powerfully. It contrasts with the parasympathetic division, which promotes rest and digest functions when the body is not under stress.