The autonomic nervous system (ANS) regulates the functions of our internal organs (the viscera) such as the heart, stomach and intestines.
The flu is contagious a day before and five days to a week after its onset. Young children, people over 65, those with compromised immune systems, and people with a terminal illness are at risk of death from the flu.
A: Symptoms of the flu usually last for  seven to 14 days, with the individual being contagious beginning a day before symptoms appear through the first week of the flu, according to Flu.gov. Young children and adults with weakened immune systems sometimes remain contagious longer.