Do Now Using the numbers 1-8, put the following steps for muscle contraction in the correct order. ____ Cross-bridge forms between actin and myosin ____ Motor neuron receives an impulse ____ Acetylcholine attaches to receptor on muscle fiber ____ Muscle contracts! ____ Calcium ions attach to actin and open binding site ____ Myosin pulls actin which shortens the sarcomere ____ Calcium ions are released into myofibrils ____ Motor neuron releases acetylcholine

Create a model of muscle contraction The model must show all stages of actin-myosin binding You must label every stage and write a description  Think beyond a poster – possible ideas could include a series of photographs, short video, 3D models You may work by yourself or with 1 or 2 partner(s) Due Friday Sliding Filament Model

Slow Twitch Fibers Slow twitch fibers are a type of muscle fiber that are used during sustained activities. They are more efficient at using oxygen to generate more fuel. They fire slowly and therefore fatigue slowly. If you do exercises like running or cardio, you will work on slow-twitch fibers. Slow twitch fibers get better and better at working over long periods of time and will become less prone to fatigue.

What are slow-twitch fibers? What types of activities use slow-twitch fibers? Give at least 3 specific examples. If you work out slow-twitch fibers, what benefits would you see during exercise? What types of athletes do you think have the most slow-twitch fibers?

Fast Twitch Fibers Fast twitch fibers are a type of muscle fiber that are used for short-term activities. They use anaerobic metabolism to create fuel so they generate short bursts of strength or speed and fire rapidly. If you do short-term, high-stress exercises then you work on fast-twitch fibers. Things like sprinting & jumping use fast-twitch fibers. These fibers are in charge of strength and power. They can get stronger and will be able to do more the more your work on them.

What are fast-twitch fibers? What types of activities use fast-twitch fibers? Give at least 3 specific examples. If you work out fast-twitch fibers, what benefits would you see during exercise? What types of athletes do you think have the most fast-twitch fibers?

Muscle Fatigue When you use your muscles for a long time, they get tired. Your muscles start by using glucose (sugar) and oxygen in order to get energy. They get their oxygen from a special type of blood called myoglobin. Myoglobin only works in muscles and makes it so more oxygen is available to the muscles. When muscles run out of oxygen, they switch to anaerobic metabolism which makes less energy and produces this stuff called lactic acid. As the lactic acid builds up, your muscles are not able to work as well and they get pooped out!

What role do glucose and oxygen play in muscle action? What is myoglobin? How does myoglobin work hand in hand with muscles? What is anaerobic metabolism? Why does your body produce lactic acid and what happens when you get too much of it?

How do you get buff? When you build up muscles, your muscles are adding more Actin and Myosin. You don’t gain more muscles or muscle fibers, you gain more protein fibers. These protein fibers (actin and myosin) make the muscles bigger and stronger. If someone has huge muscles, does that mean they have more muscles than the average person? If you work out a lot are you making more muscle fibers? What are the two examples of protein fibers that make up muscles? When your muscles get larger, what are you gaining more of?

If you don’t use it, you lose it! If you don’t use muscles for an extended period of time, then you will lose them. Your bicep won’t actually DISAPPEAR, but you will lose the protein fibers that make up the muscle. Once you lose this actin and myosin, the muscle becomes weaker and eventually turns into fat. The process of muscle degradation (loss) is called muscle atrophy. What happens if you were to stop using your muscles? What disappears when you stop working out your muscles? What do your muscles turn into? What does degradation mean? What is muscle atrophy?

Name the muscles – try without your notes!