Muscle Contraction Lab Report

The primary focus of the experiment is to see if and by how much the muscles contract depending on the solution added onto them. We learned that muscles contraction occurs in three stages excitation, contraction coupling, and relaxation. Muscles begin contraction when they are stimulated and then become more permeable to NA+. The muscle cell lets in more Na+ which causes the cell to depolarize, and also lets out K+. The release of K+ repolarizes the cell, and this quick depolarization and repolarization creates Action Potential. The creation and spreading of Action Potential across the T Tubules causes the release of calcium ions from the sarcoplasmic reticulum. The calcium ions bind to troponin on the actin myofilaments, which in turn activates

We put the muscle bundle on a petri dish and used two glass teasing needles to separate the muscle bundle into three strands 1 millimeter thick. After the muscle strands were separated, each single strand was put onto a microscopic slide and labeled A,B,C. We went to collect the three solutions which were a) 0.25% ATP plus 0.05 M KCl plus 0.001 M MgCl2 in distilled water, b) 0.25% ATP in triply distilled water, and c) 0.05 M KCl plus 0.001 M MgCl2 in distilled water. We returned and straightened out the muscle strands on the microscopic slides, so that we could measure them using the millimeter ruler prior to adding the solutions on there. After we had measured each strand and recorded it, we added four drops of each solution through an eyedropper to each corresponding slide. We waited 30 seconds before remeasuring the strands. I asked to wait some more after measuring the first time, since every slide hadn’t experienced a change yet. We remeasured again in 30 seconds and recorded those results. Then, we did the math to find out what percentage had each strand contracted after being exposed to one of the solutions. We used to formulas to find the net change ( Initial length (mm) minus Ending Length(mm) = Net Change(mm) ) and another to find the percentage that they contracted ( (Net Change(mm) divided by Initial Length(mm)) multiplied by 100 = % Change in

The measurements for Strand A beginning with the length before adding the solution A(ATP only) was 13 mm, after adding the solution the strand contracted to 11mm. The net change was 2mm and the percentage of contraction of the original length was 15%. The measurements for Strand B beginning with the length before adding the solution B(ATP and Salts only) was 7 mm, after adding the solution the strand contracted to 5mm. The net change was 2mm and the percentage of contraction of the original length was 29%. The measurements for Strand C beginning with the length before adding the solution C(Salts only) was 11 mm, after adding the solution the strand contracted to 11mm. The net change was 0mm and the percentage of contraction of the original length was 0%. My hypothesis was wrong and completely fell on its face by not even contracting. I forgot to remember that without ATP a reaction wouldn’t be able to occur. The Salts help the reaction function more efficiently but it can’t start the reaction itself. The Strand that had both ATP and Salts had the highest contraction rate but not the biggest net change. This might be due to the fact that we didn’t make the strand long enough compared to the