Respiratory Air travels into your body through your mouth or nose, travels down your trachea, then to your left and right bronchi which branch into bronchioles and finally into very small sacs in your lungs called Alveoli.
Muscular For example, while the elbow flexors biceps contract when performing a curls the elbow extensors triceps extend . A synergist helps a larger agonist work efficiently. Synergists provide additional pull or may stabilize muscles.
Excretory as your cells break down amino acids, they produce a dangerous toxin known as urea. The cells of your body excrete this urea into your blood.