Skeletal Muscle Physiology Lab Report

Using electrodes on the bicep to record the motor unit recruitment during all four conditions: control, stretching, cardio, and aerobic stretching. As shown in figure 5, the control group and the stretching are similar in the amount of EMG amplitude (mV). However, when comparing stretching with both cardio and aerobic stretching there is an increase as the intensity of the warm-up. Moreover, aerobic stretching has the highest EMG amplitude, which shows that there is motor unit cycling. Motor cycling provides a more efficient performance on the bicep because more of the muscle is being used (Widmaier, et al.,

Muscle contraction can be understood as the consequence of a process of transmission of action potentials from one neuron to another. A chemical called acetylcholine is the neurotransmitter released from the presynaptic neuron. As the postsynaptic cells on the muscle cell membrane receive the acetylcholine, the channels for the cations sodium and potassium are opened. These cations produce a net depolarization of the cell membrane and this electrical signal travels along the muscle fibers. Through the movement of calcium ions, the muscle action potential is taken into actual muscle contraction with the interaction of two types of proteins, actin and myosin.

The results in Figure 2. show that increasing the stimulus strength (V) from 0 to o.40V will result in an increase of Active Muscle force generated by the gastrocnemius muscle in the Buffo Marinus, confirming the hypothesis. The force generated plateaus when the stimulus is beyond o.40V.

Introduction: According to the “Human Physiology Laboratory Manual “,BIOL 282 ,page 31 , the reason of performing this experiment is to learn how the muscle contraction occurs based on the molecular level and what kind of factors are involved .As a matter of fact, skeletal muscles contain a lot of nuclei because of the cell fusion while being developed and are made of cylindrical cells that have myofibrils. The myofibrils contain sarcomeres and the

According to the results, the time of prior exercise and the average number of cycles after the exercise were inversely proportional. The time of prior exercise assumed to be approximately proportional to the amount of exercise. Also, the number of cycles presumed to be inversely proportional to muscle fatigue. This is because greater muscle fatigue would prevent faster rate of muscle contraction, this would result in performing a lower number of cycles during a given period. Hence, based on the graph, it was inferred that the amount of previous exercise and muscle fatigue would have a positive linear relationship. This implies that as the amount of previous exercise increased the macule fatigue increased accordingly.

The EMG signal that is observed through the placement of electrodes on the skin is closely coupled with the generation of muscle force. In normal conditions, the force-EMG relationship is either linear or the increase in EMG at low force levels is less than proportional (Semmler 2014). However, a different force-EMG relationship was observed following eccentric exercise,

O B J E C T I V E S 1. To define these terms used in describing muscle physiology: multiple motor unit summation, maximal stimulus, treppe, wave summation, and tetanus. 2. To identify two ways that the mode of stimulation can affect muscle force production. 3. To plot a graph relating stimulus strength and twitch force to illustrate graded muscle response. 4. To explain how slow, smooth, sustained contraction is possible in a skeletal muscle. 5. To graphically understand the relationships between passive, active, and total forces. 6. To identify the conditions under which muscle contraction is isometric or isotonic. 7. To describe in terms of length and force the

Their standing reach is determined by reading the Vertec’s set height and then adding the vanes – red vanes are every six inches, white vanes are every half inch, and blue vanes are every inch. Next you determine the subjects jump height giving them one preparation squat

A twitch is a contraction caused by one action potential. HYPOTHESIS!!!!!!!!!!!!!!!! In experiment 2, we measured muscular twitch in the thumb by using a finger pulse transducer and attaching a stimulus electrode to send shock through the ulnar nerve in the wrist. In experiment 3, we observed summation and tetanus by opening a new chart window, and placing the bar stimulus on the left wrist to send impulses to. In experiment 4, we measured the electrical activity of the median nerve stimulation by using the Bio Amp and the bar stimulus to stimulate the median nerve in the wrist and elbow.

Review Sheet Results 1. Describe how increasing the stimulus frequency affected the force developed by the isolated whole skeletal muscle in this activity. How well did the results compare with your prediction? Your answer: When the stimulus frequency was at the lowest the force was at its lowest level out of all of the experiments. As the stimulus frequency was increased to 130, s/s the force increased slightly but fused tetanus developed at the higher frequency. When the stimulus frequency was increased to the amounts of 146-150 s/s, the force reached a plateau and maximal tetanic tension occurred, where no further increases in force occur from additional stimulus frequency. 2. Indicate what type of force was developed by the isolated skeletal muscle in this activity at the following stimulus frequencies: at 50 stimuli/sec, at 140 stimuli/sec, and above 146 stimuli/sec. Your answer: At 50- Unfused

Activity 1: Investigating the Refractory Period of Cardiac Muscle Results: Briefly describe what happened when you applied the electrical stimuli to the heart. (1 mark) RESULTS: Applying single shocks in succession or multiple stimuli to deliver shocks at 20 stimuli/sec led to the formation of successive double peaks with a period of pause between them. This doublet is the normal systole closely followed by the extrasystole resulting from external stimulation, and then compensatory pause so the heart may resume normal beating afterwards if there is no further stimulus. Question 1: The refractory period of cardiac muscle cells is significantly longer than the refractory period of skeletal muscle cells.

1. As you increase voltage to the muscle describe how it responds to the increased stimulus.

A 2.99 kg textbook was placed in the subjects’ flat hand and held at shoulder height until instructed to extend their arm in the vertical

In my tests I started by applying no stimulus voltage to the muscle and measured the muscle length, active force, passive force, its total force and length of the latent period. As I slowly increased the amount stimulus voltage from applied to the muscle 0.0V up to 10.0V, I was able to notice some small change in the muscle itself. Although the length of the muscle never changed throughout the experiment (always starting at 75mm), the amount of force it exerted did. The table illustrates that with an increase in voltage, the amount of grams of force the muscle produced increased along with it. Passive force stayed at zero throughout the experiment because I used a stimulus to activate the muscle contraction. Lastly, I compared the duration of the latent period. As the

Post-lab Quiz Results You scored 50% by answering 2 out of 4 questions correctly. 1. Which of the following is not one of the ways that the body can increase the force produced by a skeletal muscle? Your answer: b. application of high-frequency stimulation by a motor neuron Correct answer: d. application of higher voltages to the whole muscle 2. When a muscle receives a stimulus frequency that causes non-overlapping twitches to follow each other closely in time such that the peak tension of each twitch rises in a stepwise fashion up to a plateau value, the result is known as You correctly answered: c. treppe. 3. In this experiment the isolated skeletal muscle was repetitively stimulated such that individual twitches overlapped with each other and resulted in a stronger muscle contraction than a standalone twitch. This phenomenon is known as You correctly answered: c. wave summation. 4. Wave summation is achieved by Your answer: c. summating action potentials so that their depolarizing magnitude is greater. Correct answer: a. increasing the rate of stimulus delivery (frequency)