Twitch Duration Lab Report

* 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

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.

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

5. What effect did temperature have on muscle contraction? Do some outside Internet research (cite your sources) and explain.

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

Smooth muscle cells of the ileum spontaneously contract due to the presence of pacemaker cells, called Cajal cells (Widmaier et al., 2014d). However, these smooth muscle they are also innervated by autonomic nerves, which can be stimulated to change contraction rates by stimulating. Figure 1, shows the effect of nerve stimulation of 17volts on isolated ileum tissue. Stimulating sympathetic (sympathetic nerves was stimulated for this particular tissue), causes release of noradrenaline, which inhabits contraction of smooth muscle cells. Furthermore, according to table 1, there is a -58.83% change in contraction amplitude. It can be extrapolated that fewer smooth muscles are contracting. At lower voltages, a weaker response was observed, as voltage is increased a stronger response was observed. Increasing the voltage, means more neurons are being recruited (Widmaier et al., 2014b). In this particular experiment, stimulation of nerves around the mesenteric artery caused an inhibitory response, therefore at higher voltages, more smooth muscles are being inhibited.

2. What was the smallest voltage required to produce a contraction (the threshold voltage)? What proportion of the fibers in the muscle do you think were contracting to produce this small response?

During A, ACh has been released which made an action potential. Then at B, summation is occurring because the action potentials are happening in an extended period of time. The summation of the action potentials will cause the muscle fiber to not relax since it can’t lose any tension while action potentials are occurring. Afterwards, during C, tetanus occurs which is when the maximum level of contraction of muscle fiber is happening. Finally, at D, the tetanus decreases and shows that the action potentials are starting to generate at a lower rate which also represents the muscle fiber relaxing and losing its built up

The purpose of this experiment was to study the anatomy of human reflexes, specifically to compare monosynaptic reflexes to polysynaptic reflexes. The monosynaptic reflex in this experiment is the myotactic, or Hoffman, reflex that will be seen by simulating the tibial nerve and the polysynaptic reflex is the vestibulo-ocular reflex that will be seen by spinning the subject in a spin chair.

Jeffrey D Petersohn and Dr. Lee have been gathered that and are congruent with the aforementioned needs. Both clinician expressed difficulty recognizing the paraspinal muscle twitch near motor-threshold as well as confusion between mechanical artifacts caused by the heart-beat or subject movement and the elicited motor twitch. Additionally, a visible paraspinal muscle twitch at L5 is cannot be resolved through visual inspection, regardless of stimulation intensity. Clinical observations in the OR of both clinicians did, however, suggest that activation of the intrinsic back muscle at L5, can be recorded using EMG. Such use of EMG electrodes also allows for greater sensitivity to motor thresholds when compared to visual inspection. The motor-thresholds that are identified visually, are far greater than those determined with EMG (Westin et al., Clin Neurophysiol 2014; 125: 142-147). As such, low levels of muscle activation (i.e. threshold) cannot be reliably discerned by visual inspection. Additionally, when ultrasonography was used as an additional visualization tool during clinical studies, sole activation of the multifidus muscle was seen without a visible paraspinal muscle twitch. Conversely, when the iliocostalis and longissimus muscles were activated, a paraspinal muscle twitch was visible, even when the multifidus was not being

The current tracing does not dip as much but gradually decreases as the muscle fatigues.

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)

The experiments quantitative data was collected by completing the experiment, through the involvement of the participants, and then recording the results. The data gathered provides information to be interpreted by those involved in the research experiment and draw conclusions about the results in comparison to the hypothesis. The quantitative data from the reflex blink experiment recorded the frequency that the reflex was demonstrated both with and without a blow of air. This information allows for an accurate determination of whether the initial hypothesis was correct and allows for simple comparison to results of similar studies.