1. Mechanism of muscle contraction

2. The sliding filament Theory The way that muscles actually contract and shorten is a theory called the sliding filament theory This theory involves the movement of the microscopic thin (actin) and thick (myosin) filaments

3. the Sliding Filament Theory In this theory we need to look at the relationship between the actin filament and the myosin filament These filaments are going to work together in order to cause the contraction

4. All over the thick filaments there are small heads that protrude from the body of the filament called myosin heads They myosin heads will attach themselves to binding sites on the thin actin filament.

5. The binding sites are exposed and activated when calcium ions are present This allows myosin to bind temporarily to the actin filament The myosin then acts as oars to “row” in the thin filament

7. Energy for Muscle Contraction Muscles always need energy for muscle contraction Muscles can only use energy stored in the form ATP (Adenosinetriphosphate) Muscles only store 4-6 seconds worth of ATP therefore ATP needs to me made constantly

8. ATP creation There are three ways in which ATP is created in the body Direct Phosphorylation of ADP Aerobic respiration Anaerobic respiration

9. Direct Phosphorylation of ADP The body can directly Phosphorylate ADP into ATP This means that ADP and Creatine phosphate come together to set off a reaction that will create ATP and Creatine

10. Aerobic Respiration Aerobic respiration is how ATP is generated through cellular respiration in the presence of oxygen Aerobic respiration involves glycolysis, the Krebs cycle, and the electron transport chain.

11. Anaerobic respiration The human body can also get ATP from Anaerobic Respiration The method of Anaerobic Respiration is the fermentation of lactic acid

12. Muscle Fatigue If we exercise our muscles strenuously for a long time, muscle fatigue will occur. A muscle will become fatigued when it is unable to contract even though it is still be stimulated

13. Muscle fatigue Without rest an active muscle begins to tire and contracts more weakly until lit finally ceases reacting and stops contracting. This is believed to be from the oxygen debt that occurs during prolonged muscle activity.

14. Oxygen Debt The oxygen debt is what happens when a person is not able to take in oxygen fast enough to keep up with the muscles when they are working hard. The oxygen debt will cause lactic acid to build up from anaerobic respiration and the muscles supply of ATP will dwindle.