Nerve Conduction Study Nervous System

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.,

* Electromyogram- Measures electrical activity of muscles at rest and during contraction. These studies measure how well and fast the nerves can send electrical signals.

The more stimuli per second, the greater the force generated by the muscle due to a

Encyclopedia of Nursing & Allied Health. Bioelectricity: Transmission of nerve impulses to muscle. Retrieved on 26 June 2011 from http://www.enotes.com/nursing-encyclopedia/bioelectricity

During the baseline measurement (Figure 1), when the setup was not actively manipulated, low amplitude, but still clearly visible signals where observed. This suggest that the skin contains receptors which constantly to respond to very subtle changes in the environment. Since the experimental conditions (temperature, air pressure, vibrations of the setup) were relatively stable throughout the baseline measurement, only receptors with a very low threshold of activation could respond. Since then only a relatively few number of primary sensory neurons are excited to the point that they fire APs, the amplitude of the CAPs that were measured were low.

2. Discuss the biological processes that explain why peak contractile force changes with different stimulus strengths.

Next with a stimulation duration of 50us, the stimulus amplitude should be set to the maximal tolerable stimulus intensity. With stimulus frequency of 2Hz, observe and record the leg movement, increase it by 5Hz but should not exceed 50Hz. With the electrodes connected to the analogy output channel and ground of the DAQ board. With the corresponding LabVIEW program, the frequency and amplitude (voltage) of the stimulation supplied to the leg can be controlled. With this the “sweet spot” of the lowest amplitude and best frequency to cause evoked movement can be found and recorded. Now the stimulation frequency should be set to 10Hz and the duration of stimulation pulse to 5ms or less. The range if leg movement changes can be observed as amplitude changes. Electrical stimulation in increments of 0.01V should be delivered and the minimal voltage required to generate muscle twitch should be recorded. The pulse duration should then be increased by durations of 10ms and the minimum voltage should be recorded this should be repeated for a variety of pulse

In this exercise, you examined the effect of increasing stimulus intensity on the nerve. What other stimulus parameter

• Nerve conduction studies. These record muscle activity and check how well your muscle nerves send signals.

1. Click the Stimulate button once. Because the beginning voltage is set to zero, no muscle activity should result. You will see a blue line moving across the bottom of the oscilloscope display. This blue line will indicate muscle force in the experiments. If the tracings move too slowly across the screen, click and hold the

To test the muscle strengths the subjects were required to use the one repetition maximum method for a variety of different exercises. The experiment consisted of the subjects rising from the chair without the use of their hands. During the trial reflective markers were

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

• Once your muscles have been studied at rest, your health care provider will ask you to contract or flex your muscles. The electrodes will send a signal that tells the electrical activity of your muscles.

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

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)