1. Coordinated Movement Objectives: Describe how coordinated movement requires the action of skeletal muscles about joints, with reference to the elbow joint. Compare and contrast the action of synapses and neuromuscular junctions.

2. Coordinated Movement This involves the interaction of the nervous system with the voluntary muscle attached to bones. Nerves stimulate the muscles to contract, so the muscles pull on the bones to move them.

3. Muscles are attached to bones with tendons made of inflexible collagen. Muscles cannot push only pull. They usually work in antagonistic pairs to move bones one way and the other at a joint. The muscle that bends the limb at the joint is known as the flexor (biceps), while the muscle that straightens the limb at the joint is known as the extensor (triceps). The elbow joint is an example of a synovial joint. These joints occur where a large amount of movement is needed. The synovial membranes secrete synovial fluid to lubricate the joint and prevent friction between the bones. Ligaments attach bones to each other to prevent dislocation of the joint. Use your text book page 232 to label your diagrams of the elbow joint.

4. A muscle is composed of muscle fibres (cells). Each fibre is very long and has several nuclei. Surrounding each fibre is a plasma membrane known as the sarcolemma. Each fibre is made of several myofibrils. Each myofibril is surrounded by extensions of the sarcolemma known as T- tubules. Sarcoplasmic reticulum extends out from the T- tubules. Each myofibril consists of actin and myosin protein filaments arranged in sarcomeres, that give skeletal muscle its characteristic appearance. Skeletal Muscle Structure

5. The Neuromuscular Junction

6. Events at the Junction Watch the following animation of the events at a neuromuscular junction (you may want to make rough notes)animation Now use your text book (page 232) to construct a flow chart for the process. Try to add in any extra detail you gained from the animation.

7. Label your diagram of the motor end plate. Annotate your labels with biological significance e.g. why is the sarcolemma folded? How does that make it better adapted to its function? Why does the axon terminal contain many mitochondria. What is the purpose of the T-tubules etc.?

8. The Motor Unit

9. Motor Unit Ratios: what do you notice? Gluteus maximus (butt muscles!) – 1:1000 Back muscles – 1:100 Finger muscles – 1:10 Eye muscles – 1:1 FORCE OF CONTRACTION vs. PRECISION OF MOVEMENT

10. Homework Draw up a comprehensive table of the similarities and differences between synapses and neuromuscular junctions. Explain the difference between twitch and tetanus, and how these contractions are brought about.