Answer:
I will attempt to answer your question.
When the marathon runner begins to run there is the need for increased circulation for blood, nutrients,oxygen,etc to reach vital centers of the body, as an adaptation to the increased muscular activity. Baroreceptors in the coronary artery and the arch of the aorta detect the increase in blood pressure(this becomes the stimulus) and send signals to the brain (control center) that is the cardiac center located in the medulla oblongata. The motor response goes to the smooth muscles of the blood vessels to dilate and for the heart to beat faster. This is one way
Also, the respiratory rate needs to increase so that there will be enough supply of oxygen and removal of CO2 and this is controlled by the sympathetic division of the autonomic nervous system. So the person begins to breathe faster in order to produce more glucose. There is increased glycogenolysis to quickly convert glycogen (by glucagon) into glucose. This will avail enough energy for the brain and cardinal organs. This is two
Again, as the runner runs, excess heat build up must be reduced which is achieved through sweating so that the body begins to cool down or regulate it's temperature. This is three
There's a lot more...
