Final answer:
Quiet breathing (eupnea) occurs at rest without conscious thought, while forced breathing (hyperpnea) is an active mode of breathing that can occur during exercise. They involve different muscle contractions and control lung volume.
Step-by-step explanation:
There are different modes of breathing, and quiet breathing (eupnea) and forced breathing (hyperpnea) are two of them. Quiet breathing occurs at rest and does not require conscious thought. It involves the contraction of the diaphragm and external intercostal muscles. On the other hand, forced breathing can occur during exercise or actions that require active control of breathing. During forced breathing, accessory muscles of the neck and abdomen also contract to increase lung volume and push more air out.