Question

For each of the following activities. Explain how your skeletal muscles will use the three possible ATP sources: the phosphagen system, lactic acid fermentation, and aerobic cellular respiration (not all will be used in each situation).

A hint: when you drastically increase your activity level, your heart rate and respiration rate will take some time to speed up to meet the increased O2 needs. Unless your activity level is more strenuous than your heart rate and respiration rate can accommodate, they will be able to “catch up” and provide adequate O2 delivery after several minutes.

4. You get up from a nap and walk to the kitchen to make a sandwich. It is a fancy sandwich, so it takes you 10 minutes to make it.
5. You are sitting calmly on the couch watching your favorite show.
6. You are sitting calmly on a park bench when a grizzly bear starts coming toward you. You must run away at FULL SPEED (beyond your fitness level) for 15 minutes before you lose the bear.

Answer 1

The three ATP sources are used based on ATP requirement and oxygen availability.
Basically - at rest we use aerobic
Sudden movment - short period of time, few seconds - used phosphagen system based on creatine
Rapid response - lactic acid

1. Get up from bed and wait for 10 minutes to make the sandwitch. No strenous exercise, but since you are hungry glucose is low in blood. So body uses stored glycogen and carries out aerobic cellular respiration.

2. Sitting calmly on couch - resting phase, aerobic cellular respiration.

3. Running - initially the rapid burst of ATP is provided by Phosphagen system for few seconds. Later Anerobic respiration (lactic acid) takes over to supply rapid ATP to muscle cells.