Final answer:
The statement is true. An increase in CO₂ levels is a normal stimulus to breathe, making the initial statement true. The diaphragm can be controlled both consciously and automatically. Hypoventilating is inadequate breathing and is not described accurately as fast and shallow; thus, that statement is false.
Step-by-step explanation:
An increase in CO₂ levels in the blood (hypercapnea) is a normal stimulus to breathe. The respiratory centers in the brain control the respiratory rate and depth, and they respond to chemical and pH changes in the blood. Central chemoreceptors in the brain, as well as peripheral chemoreceptors in the aortic arch and carotid arteries, are responsible for detecting these changes.
When carbon dioxide levels rise, it leads to an increase in hydrogen ion concentration (H+), making the blood more acidic. This acidotic state is detected by the chemoreceptors, which in turn stimulate the respiratory centers to increase ventilation. This is the body's way to expel excess carbon dioxide, hence reducing H+ concentration and returning the blood pH to normal.
Additionally, the diaphragm can indeed contract under conscious control, which is utilized during activities such as speaking, singing, or voluntary breath holding. Thus, our ability to alter breathing patterns voluntarily confirms that the diaphragm can be controlled consciously as well as automatically by the respiratory centers.
The term hypoventilating refers to breathing that is inadequate to meet the oxygen demands of the body, not necessarily fast and shallow. Therefore, the statement defining hypoventilating as fast and shallow breathing is false. Hypoventilation typically results in an insufficient exchange of gases, leading to an increase in blood carbon dioxide levels.