# Twitch and Contraction Summation Powerphys

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LABORATORY REPORT Activity: Name: Instructor: Date: Twitch Contractions and Summation Predictions Effect of Muscle Fiber Length on Contraction 1. As muscle fiber length increases contraction force decreases Effect of Stimulation Frequency on Contraction 2. As the frequency of stimulation increases, the force of contraction: increases Materials and Methods Measurement of Threshold Stimulus Dependent Variable contraction force Independent Variable stimulation voltage Controlled Variables temperature, frequency of stimulation, muscle fiber length Effect of Muscle Length on Contraction Dependent Variable contraction force Independent Variable muscle fiber length Controlled Variables temperature, stimulation voltage, frequency of stimulation Effect of Stimulation Frequency on Contraction Dependent Variable contraction force Independent Variable frequency of stimulation Controlled Variables temperature, stimulation voltage 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). It is because the temperature is near the mouses normal temperature. Laboratory Report/ Kaitlyn Manuel/ Twitch Contractions and Summation/ Dr. McMasters/ 10.18.2014/ Page [1] of [4] 6. At a stimulation frequency of 15 Hz how many stimuli were there per second? There were 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 0.105 500 mV 0.105 Effect of Stimulation Value on Twitch Contraction Force 1. What is the threshold stimulus? The threshold stimulus is 400 mV. 2. What is the maximum force generated at the threshold stimulus? The maximum force was 0.105 gf. 3. How does increasing voltage above threshold stimulus affect force development? It will distribute the