1. Do Now 1. Draw a picture of a sarcomere
2. Label actin, myosin, Z-line, H-zone, I band, A band
3. What is the difference between actin and myosin?
4. List the hierarchy of muscle structures starting with the whole muscle down to myofilaments.

2. Explain how muscles contract Describe the sliding filament model
Today….
Explain how muscles contract
Describe the sliding filament model
Compare and contrast origins, insertions, agonists, and antagonists

3. For the purposes of this class…
You will need to know 8 steps to muscle contraction
p in your textbook is your best friend

4. Step 1- p.341
Motor neuron receives an impulse

5. Motor Unit or Neuromuscular Junction
1.  Neuron         2.  Sarcolemma   (or motor end plate)       
3.  Vesicle      4.  Synapse        5.  Mitochondria

6. Step 2 – p.341
Motor neuron releases the neurotransmitter acetylcholine into the gap between the neuron and the muscle

8. Step 3 – p.342
The acetylcholine attaches to receptors on the muscle fiber membrane

10. Step 4 – p.342
The muscle responds by releasing calcium ions into the myofibrils

11. Step 5 – p.345
The calcium ions attach to the Actin and unlock the binding site

12. Step 6 – p.345
The cross-bridges from the myosin attach to the binding sites

14. Step 7 – p.345
The cross-bridges fire and pull the actin which shortens the sarcomere

16. Step 8 – p.345
All of the shortening sarcomeres lead to shortening (contracting) of the muscle

17. What is rigor mortis?
A few hours after a person or animal dies, the joints of the body stiffen and become locked in place. This stiffening is called rigor mortis. Depending on temperature and other conditions, rigor mortis lasts approximately hours. The phenomenon is caused by the skeletal muscles partially contracting. The muscles are unable to relax, so the joints become fixed in place.

18. What is tetanus?
Tetanus causes cholinosterase to not break down the acetylcholine in the synapse.  This results in a person's muscles contracting and not relaxing.
A tetanus shot must be administered shortly after exposure to the  bacteria.
Once you develop tetanus, there is no cure.

19. Sliding Filament Model
Create a model of muscle contraction
The model must show all stages of actin- myosin binding
Think beyond a poster – possible ideas could include a series of photographs, short video, 3D models
You may work by yourself or with a partner

20. How Skeletal Muscle Moves

21. Muscles ♥ Bones
Muscles and Bones work together to create MOVEMENT!

22. Origin vs. Insertion Origin = the immovable end of the muscle
Insertion= the movable end of the muscle
Typically, the origin lies proximal to the insertion

23. Contract that muscle!
When a muscle contracts, it shortens & thus pulls the insertion closer to the origin

24. Extension vs. Flexion Extension = increases the angle of joint
Flexion = decreases angle of joint

25. *The same muscle can do both!
Think about one of the quad muscles (rectus femoris)
EXTENSION at the knee joint
FLEXION at the hip joint

26. With your groups… List three examples of flexion
List three examples of extension

27. Agonists, synergists, antagonists
Agonist = main muscle
Synergists = assist & stabilize the agonist
Antagonists = capable of doing opposite movement

28. Example: Bicep curl Agonist = Synergists = Antagonists= Biceps!
Pectorals, deltoids, laterals, trapezius
Antagonists=
triceps