1. All Exercise Occurs at the Cellular Level So how does a muscle cell work – allowing us to move during exercise?

2. The Muscle Cell is King Can increase work 100X in 30 seconds No other cell can do this It will also demand that the rest of the body will join it – Commands the heart to send fuel – Commands the lungs to send oxygen

3. Muscle Review Specialized to contact Cells provide a long axis for contraction Multinucleated Many Mitochondria Can be: – Skeletal – Cardiac – Smooth

5. Chemical Structure of Skeletal Muscle 75% Water 20% Protein 5% Chemicals that create a contractile environment – Inorganic salts, high energy phosphates, urea, lactic acid, minerals (calcium, magnesium etc), enzymes, ions, amino acids, lipids, carbohydrates

6. How Does a Muscle Really Contract? Read Muscle Contraction and Reaction Summarize this page What is new here to us?

7. Muscle Contraction Animation Watch – Muscle Contraction Animation

8. It all starts with a nerve A nerve cell is like all other cells of the body An action potential (electrical impulse) passes down a nerve fibre from the brain etc to working muscles Each neuron (nerve cell) will form into a motor unit to make the connection into the muscle fibres

9. What happens when muscles contract – Physically? Myosin heads bind to actin (thin) and they pull the actin to the centre sliding past the myosin (thick) ATP is used to break this bond and attach the myosin further down the line 350 heads of myosin attach and reattach 5X per second

10. Muscle Contraction

11. Why doesn’t it happen all the time The regulatory protein tropomyosin is the brake or blocking device A calcium ion (Ca 2+ ) binds with the troponin which releases the blocking action of the regulatory protein tropomyosin by pulling it into the groove of the actin strands therefore exposing the binding sites on the actin

12. What initiates the calcium release? The sarcoplasmic reticulum is an ER which transports and regulates Ca 2+ An action potential arrives from the motor neurons via the transverse tubules to the SR. This changes the membrane of the SR and releases Ca 2+

13. When does contraction stop When the motor neuron action potential passes, the SR pumps the Ca 2+ back into itself This causes the binding site on the actin to now be blocked

14. In isolation all a muscle needs is energy (ATP) Watch - Issolated Rabbit Muscle in an ATP solution

15. Review – with Lego? Watch - Lego Muscle Contraction Video

16. How could we improve the Lego model?