They use quorum sensing; cell to cell. Which gives larger groups of organisms syncronizing abilities for activities.
Your body produces two hormones when under stress, called cortisol<span> and adrenaline. They are produced in part of the endocrine system called the adrenal glands. ... They typically don't </span>get<span> a lot of press, which is a shame, as they work especially hard both during </span>menopause<span>, and when we experience chronic stress.</span>
They can help to motivate or unmotivated you. If other members are lazying around, this can make it hard for you to find the motivation to work out
Hope this helps