Unit Three Lab- Limb

Build A Limb Lab

For this project I chose to model the arm and try to show how movement happens. I am going to show the bones involved, the joint that connects them, muscle and how muscle works at the cellular level to cause contraction. Muscle contraction starts with a nerve impulse when polarity across the axonal membrane occurs. This causes and action potential that opens the sodium and potassium gates and travels from one Ranvier node to another down the axon. One motor neuron interacts with many muscle fibers at the axon terminal. At the terminal synaptic vessels release ACh which binds to sarcolemma receptors. Impulses are passed from here down the T tubules to the reticulum where calcium is released and leads to sarcomere contraction. Actin slides over myosin and binds causing the release of ADP. ATP is then needed to break this bond. By muscles contracting they pull only one way and thus usually two muscles work together.

The following is a list of materials used and what they represent

1. Hedger handles- Humerus, radius and ulna
2. Popcicle sticks- elbow joint (trochlea),myosin
3. Red Yarn- biceps brachii
4. Pipe cleaners- cross bridges of myosin (blue), Actin (white), Axons (white), dendrite (white), T tubules (green)
5. Styrofoam balls- different neurons
6. Electrical tape- myelin sheath
7. Hot glue- sensory receptors
8. Wire- Z lines
9. Clear tubing- sarcolemma, myofibril (with red lines)
10. Markers and paint- used to add color to myofibril and axon terminals

This first picture is of the bone structure showing how the humerus connects to the radius an ulna by the elbo joint. This is a hinge joint and can only bend one way. The joint is represented by a roll of popsicle sticks. They represent the trochlea and capitulum .

The second picture shows the red yarn representing the biceps brachii. It is attatched to the top of the humerus and scapula (origin) and also to the radius (insertion).

The third and fourth picture show the sarcomeres in a myofibril when they are relaxed and also when they are contracted. The sarcomeres contain actin and myosin. When the impulse travels down the t tubules (fifth picture), calcium is released into the sarcoplasmic reticulum causing the sarcomeres to contract (actin slides past myosin) and shorten.

This 5th picture is a model of skeleton muscle fiber with T tubules, sarcolemma, and myofibril with z lines.





The last picture is of the different types of neurons, their axons, dendrites, and myelin sheath. The neurons are responsible for taking impulses from the CNS, summing up these impulses, distributing them to and effector to carry out the response.

In conclusion this model shows the different units involved in muscle movement from the neurons all the way up to bones and muscles. This model was a good learning tool because when I actually had to make these aspects I had to think about their functions and understand how they worked individually and then how they all tied together.