Final answer:
The characteristics of normal, quiet breathing being effortless, even, regular, and not audible are true. It involves the diaphragm contracting without conscious effort, a process known as eupnea. Despite this unconscious default, breathing can also be consciously controlled as needed.
Step-by-step explanation:
When describing respiratory rate and the characteristics of normal breathing, one can say respirations are often effortless, even, regular, and not audible. This description is indeed true and represents a type of breathing known as eupnea, which is the quiet breathing that occurs at rest and does not require conscious effort.
However, it's important to note that breathing can also be a conscious action, for example, when holding one's breath while swimming or for particular techniques in singing. The diaphragm is the primary muscle involved in quiet breathing, where it contracts with the external intercostals to allow for inspiration and expiration.
During quiet breathing, movements are usually smooth and unlabored, unlike forced breathing or hyperpnea, which occurs during exercise or requires active thought and uses additional accessory muscles for inspiration and expiration.