1. Bellwork In the high school textbook,
Read pg 195: Providing Energy for Muscle Contraction
Summarize the 3 pathways for ATP regeneration

2. Energy for Muscle Contraction
Initially, muscles use stored ATP for energy
Only 4–6 seconds worth of ATP is stored by muscles
After this initial time, other pathways must be utilized to produce ATP
ADP + Creatine Phosphate (CP)  ATP
CP supplies last less than 15 seconds
Aerobic respiration (with Oxygen)
Glucose CO2 and H2O + ATP
Provides lots of ATP (36 ATP for every 1 glucose), but is slow process
Anaerobic Respiration (without Oxygen)
Glucose  Pyruvic Acid (without Oxygen)  Lactic Acid + ATP
Not as efficient, but fast
Need LOTS of glucose
Lactic acid = muscle fatigue

3. Lactic Acid= Muscle Fatigue
Read pg Muscle fatigue and oxygen deficit
What does it mean to have muscle fatigue?
What two factors cause muscles to contract less and less effectively and potentially stop contracting all together?
How do our bodies compensate for the accumulation of lactic acid after heavy exercise?

4. Muscle Fatigue and Oxygen Deficit
When a muscle is fatigued, it is unable to contract even with a stimulus
Common cause for muscle fatigue is oxygen debt
Oxygen must be “repaid” to tissue to remove oxygen deficit
Oxygen is required to get rid of accumulated lactic acid
Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less

5. When Eric returned from jogging, he was breathing heavily and sweating profusely, and he complained that his legs ached and felt weak. His wife poured him a sport drink and urged him to take it easy until he could “catch his breath.”
Why is Eric breathing heavily?
What ATP- harvesting pathway have his working muscles been using that leads to such a breathing patter?
What metabolic product might account for his sore muscles and his feeling of muscle weakness?