Final answer:
Activation of the sympathetic nervous system triggers the fight or flight response, increasing heart rate and inhibiting digestion, while the parasympathetic nervous system later restores normal body functions.
Step-by-step explanation:
Activation of the sympathetic nervous system is associated with the fight or flight response, which prepares the body to confront or escape from potential threats. When this system is activated, several physiological changes occur. The heart rate accelerates, air passages in the lungs expand to increase oxygen intake, blood is directed more towards the skeletal muscles, and non-essential systems like digestion are inhibited. This surge of activity is facilitated by the release of adrenaline, which enhances the body's ability to perform under stress. In direct contrast, the parasympathetic nervous system works to promote relaxation and restore the body to its normal state following a sympathetic response, relaxing the muscles, slowing the heart rate, and resuming digestion.