Unit III Lab Build a Limb

Unit III Lab

Build a Limb

In this lab I will be building a limb. This will include the muscles, skeletal bones with a joint, and an exploded view of the inner workings of a muscle cell to show how the nerve impulse (action potential) travels along the motor neuron to the muscle cell.

Here are the materials I used to make my model.

Here is the right arm with bones, muscles and an exploded view of a single muscle fiber.

Here is the muscle fiber that contains many myofibrils which are divided into sarcomeres.

This is the part of the muscle that either contracts (shortens) or relaxes (elongates).

Here is the neuromuscular junction where the motor neuron meets the muscle fiber. This is where the neurotransmitter acetylcholine (Ach) is released from the neuron and binds to the muscle receptors, then sending impulses down the T system of the muscle fiber. The T system is connected to the sarcoplasmic reticulum and Ca+ is released. The release of Ca+ causes the sarcomere to contract, resulting in the sliding actin and myosin filaments making the whole muscle contract and thus moving the arm.

In conclusion the model of the arm starts at the motion of the arm and traces back to the action potential on the motor neuron. I learned that something we take for granted everyday (the ability to be mobile) is a truly remarkable process and yet happens so quickly.

Evaluation

I believe the model and the lab work met the following criteria. Which I hope to receive a B for.

• Introduction presents model clearly
• List of limb parts explains how they are represented in the model. There is an understandable and consistent relationship between the model parts and what they are in the limb
• Model includes representation of all the basic parts of a limb listed above. It is easy to understand why each model piece was chosen to represent a certain part of the limb.
• Bone, joint, muscle, and neuron are represented. Pieces are used that make it easy to see how these elements function in the limb.
• Description of action potential and muscle contraction are presented. They are shown in their entirety and it is easy to follow how each process happens.

Presentation of model is orderly, understandable and cohesive. An effective project requires a lot of work. There is evidence that the student has thought through what pieces they want to use for each part of their limb…and WHY. It is easy to see how each piece represents that part of the limb, and to imagine how it works. The Neuron action potential and Muscle Contraction component makes sense and it is possible to follow each aspect of an action potential as it triggers the muscle to contract via the sliding actin and myosin filaments.

I believe I had fun building an arm and it definitely was fun. But where I sometimes have difficulty is just deciding what materials to actually use. Once that is decided the rest is the fun part.