Unit 3 Lab- Movable Limb

The purpose of this lab was to show how impulses through neurons stimulate movement of muscles and bones, specifically a joint. For my model, I chose to use the following materials: homemade Play- Dough, acrylic paint, and black poster board.















First, I started by assembling the limb joint. I chose a knee joint. I formed the Femur, Tibia, Fibula, and Patella, and then joined them with the Anterior Cruciate Ligament, the Posterior Cruciate Ligament, the Lateral Collateral Ligament, and the Medial Collateral Ligament (shown in blue).















Then, I started to add in the muscles and tendons. I painted each of the muscles red with pink accents, and all of the tendons white.















Then I bent the leg and showed the slight change in muscle contraction.















For the next part of the lab, I made two models of Muscle Fiber. The first one is of a relaxed Sarcomere, and the second of a contracted Sarcomere.

And last but not least, I made a model of a Neuron and the nerve impulse. It shows how the charge changes with the entering of Na+ and the exiting of K+ in the axon of the Neuron.

Through this lab, I better understand how an impulse initiates muscle movement. The neuron gets an impulse from the CNS which travels down the axon. The impulse causes the polarity of the axon to change through the exchange of Sodium and Potassium. When the impulse reaches the muscle, Acetylcholine is released into the synaptic cleft and binds to the ACh receptors. The impulse then travels down the T system of the muscle fiber, causing the muscle to contract. In the muscle fiber, Calcium binds to Troponin, exposing Myosin binding sites on the Actin. When the Myosin head is unattached, it hydrolyzes ATP. ADP + P are bound to the Myosin as the Myosin head attaches to the Actin. When the ADP + P release, a power stroke occurs, causing the head to bend and pull the Actin in toward itself. And lastly, the binding of fresh ATP causes the Myosin head to return to its resting position, causing the muscle to relax. And that is how a muscle contracts and relaxes when you bend at a joint.