Final answer:
The primary system used during the first few seconds of exercise is the creatine phosphate system, followed by the anaerobic pathway using glycogen. The Sympathetic Division of the Autonomic Nervous System orchestrates the physical changes necessary for exercise.
Step-by-step explanation:
During the first few seconds of exercise, regardless of intensity, the system primarily utilized is the one that uses creatine phosphate. This system is designed for short bursts of energy, such as those needed by weightlifters or sprinters, because it can release energy quickly but only lasts for 8-10 seconds.
After this initial phase, the body begins to use glycogen stores through an anaerobic pathway that does not require oxygen. This pathway can fuel exercise for 1.3-1.6 minutes, suitable for events like the 100-meter swim or the 200-meter to 400-meter run.
The Sympathetic Division of the Autonomic Nervous System also plays a critical role during exercise. It is responsible for the physiological changes such as increased heart rate and sweating, which are part of the fight-or-flight response but also occur during physical exertion.
As the cardiovascular system allocates resources to active tissues, blood flow is redirected from less essential areas, like the digestive system, to more critical ones, such as the muscles and lungs. This helps to provide the muscles with the oxygen they need for sustained activity.