For this project, I will demonstrate how muscles and bones work together to produce movement. For this demo, I will model the arm.
Some raw materials:
The backscratch gave his life . . .
The operation: in progress.
After careful planning and assembling, the patient experiences - movement!
An explanation:
The motor neuron (white balloon in the hand of the operator/surgeon) signals the bicep. You can see the muscle responding to the stimuli by contracting. As it contracts, the diameter of the muscle increases, as mass remains the same (is it becomes shorter, it must get larger somewhere else). If this were more anatomically correct, the muscle would also be harder during contraction. The shortening of the muscle and pulling draws the forearm upwards, pivoting on the elbow joint.
Some stills . . .
Close up of motor unit
It's hard to see the action potential coarsing along the axon, there is a slight purple color to indicate that between the schwann cells. This potential will result in a release of ACh from the axon terminals. The neurotransmitter will then bind to the receptors in the sarcolemma. Then calcium will be released from the sarcoplasmic reticulum and will bind to troponin on the actin filament.
This deposition of calcium causes the troponin to move and expose the binding sites for the myosin.
Relaxed state of sarcomere
The myosin has heads that will extend to the binding sites on the actin forming a cross-bridge and will pull the actin closer together. ADP is utilized for this action and ATP is needed for the heads to release from the binding sites.
Contracted state of sarcomere
All of these actions happen at an amazing rate. Just think about how often you move without even thinking about it. Knowing the mechanics and chemical reactions needed to move one fibril makes my head spin. Even as I'm typing this report, I am amazed (can't think of a better word) by the effortless motions of my fingers in leiu of the magnitude of activities that are needed to accomplish it.
No comments:
Post a Comment