Which cellular organelle is responsible for adenosine triphosphate (ATP) production?

A. When the inspiratory muscles contract, the length of the thoracic cavity actually increases, not decreases, as the diaphragm moves downward and the ribs expand.

B. When the diaphragm contracts (during inspiration), it moves downward into the abdomen, not upward.

C. The correct action is that the contraction of the inspiratory muscles (including the diaphragm and external intercostals) increases the diameter of the thoracic cavity, allowing for the expansion of the lungs to draw in air.

D. The chest cavity does not compress the lungs during inspiration; rather, it allows for the lungs to expand as air is drawn in.

A. Histamine does not primarily affect the respiratory rate; its main action is on blood vessels and smooth muscle.

B. Histamine is a chemical released during allergic reactions and inflammation, and one of its primary effects is vasodilation, which leads to increased blood flow to affected tissues. This can result in symptoms such as redness and swelling.

C. Histamine generally causes bronchoconstriction, not bronchodilation, which can lead to symptoms such as wheezing and difficulty breathing, especially in conditions like asthma.

D. Histamine does not directly affect heart rate, but it can influence blood pressure through its vasodilatory effects.