Veterinary Assistant Practice Exam 2025 – The Complete All-in-One Guide to Exam Success!

The primary systems responsible for controlling breathing are the mechanical control and chemical control systems. Mechanical control refers to the physical aspects associated with the mechanics of breathing, such as the diaphragm's movement and the expansion of the thoracic cavity. This is essential for air to flow in and out of the lungs.

Chemical control, on the other hand, involves the regulation of breathing based on the levels of carbon dioxide, oxygen, and pH in the blood. Chemoreceptors located in various areas of the body, including the medulla oblongata and carotid bodies, monitor these levels and send signals to adjust the breathing rate accordingly. For instance, an increase in carbon dioxide levels triggers a response to increase the depth and rate of respiration to expel more CO2 and take in more oxygen.

The other options discuss different aspects of control, such as voluntary versus involuntary control, which relate more to conscious and reflexive components of breathing, rather than the core systems driving the fundamental process of respiration. Although the sympathetic and parasympathetic systems can influence breathing patterns and response to stress or relaxation, they are not the primary controllers responsible for the act of breathing itself.