# Twitch Contractions and Summation

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LABORATORY REPORT Activity: Name: Instructor: Date: Twitch Contractions and Summation Giuliano Derteano Dr. Ayanna Alexander-Street 03.27.2015 Predictions Effect of Muscle Fiber Length on Contraction 1. As muscle fiber length increases contraction force increases, becoming maximum at an optimal length, then decreasing at longer lengths Effect of Stimulation Frequency on Contraction 2. As the frequency of stimulation increases, the force of contraction: decreases Materials and Methods Measurement of Threshold Stimulus 1. Dependent Variable undefined 2. Independent Variable undefined 3. Controlled Variables undefined; undefined; undefined Effect of Muscle Length on Contraction 1. Dependent Variable undefined 2. Independent Variable undefined 3. Controlled Variables undefined; undefined; undefined Effect of Stimulation Frequency on Contraction 1. Dependent Variable undefined 2. Independent Variable undefined 3. Controlled Variables undefined; undefined 4. What structure was stimulated to cause a muscle contraction? The motor unit was stimulated 5. Explain why the temperature of the water bath was 35 C (95 F). The water bath was 35 C was used because it is near the mouse's normal body temperature Laboratory Report/ Giuliano Derteano/ Twitch Contractions and Summation/ Dr. Ayanna Alexander-Street/ 03.27.2015/ Page [1] of [4] 6. At a stimulation frequency of 15 Hz how many stimuli were there per second? There are 15 stimuli per second Results Table 4: Measurement of Threshold Stimulus Force (gf)(Motor neuron 1) 100 mV 0 200 mV 0 Voltage (mV) 300 mV 0 400 mV 0.091 500 mV 0.091 Effect of Stimulation Value on Twitch Contraction Force 1. What is the threshold stimulus? 400 mv 2. What is the maximum force generated at the threshold stimulus? The maximum force generated was 0.09 gf. 3. How does increasing voltage above threshold stimulus