During exercise, energy demand in the muscle increases. which other body system directly provide for this demand?

During exercise, a number of changes occur to maximise the body's oxygen intake. Firstly our heart rate / pulse increases. This is due to the heart beating much faster and more forcefully to pump blood faster around the body.

Our breathing rate increases to intake more oxygen and exhale more CO2.

The smooth muscle in our trachea and bronchi relaxes to increase the lumen size thus making breathing easier. Adrenaline may also be released leading further amplifying these changes as well as reducing blood flow to the gut and thus peristalsis occurs at a much slower rate.

Also when we exercise we respire more, producing heat, which must be expelled. This may be done through sweating. Another physiological change that occurs is vasodilation of arterioles closer to the skin to allow more blood to flow closer to the skin, allowing more heat to radiate out.