Working Limb Lab Project

This project highlights the ability to show and understand the concept of a moving limb and the neuron triggering muscle to pull on bone to make a joint move. I chose the joint between the humerus and the ulna and radius at the elbow.


Limb construct equipment

I began the initial project with:

• Humerus: wide piece of trim
• Radius: wood piece
• Ulna: wood piece
• Bicep brachii and tricep brachii: rubberbands (anchored with push pins)
  
• Elbow joint: hinge and screws
  

Beginning of the elbow joint


Bicep brachii (contracted) across humerus to radius


Tricep brachii (contracted) across humerus to ulna


Humerus


Ulna and Radius

I recycled some of my cell from unit one to show a muscle fiber:

• Sarcolemma: purple ribbon
• Myofibril: groups of dark pink beads
• Mitochondria: light pink beads
• Sarcoplasm: white styrofoam

Muscle fiber

A muscle fiber slides by contraction and relaxation. When the myofibrils contract, the sacromeres shorten. Thick filaments are composed of several hundred molecules of myosin, which end in a cross bridge on the globular head. Thin filaments are primarily 2 intertwining strands of the protein actin. 2 other proteins, troponin and tropomyosin, play a role. When muscles are stimulated, impulses travel down a T tubule and calcium is released from the sarcoplasmic reticulum. ATP supplies the energy for the muscle contraction. Calcium binds to tronoponin, exposing mysoin receptor sites. Myosin then uses ATP to pull actin toward the center of the sarcomere.



Sarcomeres relaxed

Calcium binds to tronoponin, exposing mysoin receptor sites. Myosin then uses ATP to pull actin toward the center of the sarcomere.


Calcium binds to troponin, exposing myosin receptor sites.


Sarcomeres contract after myosin utilizes ATP to pull actin toward center of sarcomere

I learned a great deal in this lab regarding limb and muscle movement. The chemical reactions that take place on the microscopic level allow for the movement that we can see at a much larger level.