Skeletal Muscle: a Study of Skeletal Muscle Contraction Mechanism in Fogs and the Various Factors Affecting It

* 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

Smooth muscle contraction occurs when calcium is present in the smooth muscle cell and binds onto calmodulin to activate myosin light chain kinase (Wilson et al., 2002). Phosphorylation of myosin light chains result in myosin ATPase activity thus cross-bridge cycling occurs causing the muscle to contract (Horowitz et al., 1996). There are two known models of excitation and contraction in smooth muscle, electromechanical coupling (EMC) and pharmomechanical coupling

One criticism of this research is that it is correlational. Therefore, we cannot infer a causal

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

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

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,

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

The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state. OBJECTIVE: To become familiar with the skeletal

As the voltage was increased from threshold to maximum voltage, there was a greater force in the muscle contraction. Once the maximum voltage (2500 mv) was reached, even if there was an increase in voltage, the force of the muscle contraction remained the same.

The introduction of this lab report discussed and elaborated how muscle contraction is an intricate and precise step-by-step process in the body. The concepts outlined at the introduction intertwine with the experiments performed in this lab. The experiments aimed to showcase the physiological cause and effect of skeletal muscle responses towards various situations. For instance, the first experiment demonstrated spatial summation through the form of muscle recruitment. The cause of this reaction was due to the increased voltage input on the sciatic nerve. Furthermore, the second case study exhibited temporal summation, where constant stimulus exposure led to a fusion of twitches called a tetanic contraction. As for the third experiment, the

Henneman (1965) investigated the relationship of neuron excitability and its size in the stretch reflex of the triceps surae muscle of the decrebrated cat. His finding lead him to believe there is a set of principles dictating the order of muscle unit recruitment as dictated by size which he coined the size principle.

This is an exercise designed to demonstrate some properties of skeletal muscle using the gastrocnemius muscle of a frog. A muscle organ, such as the gastrocnemius muscle, is composed of many individual muscle fibers. A twitch is a muscle contraction the occurs in response to a single, rapid stimulus that evokes a single, isolated action potential in a muscle fiber. The contraction of a muscle fiber in response to a single action potential is likewise an all or none response. There is a minimum stimulus strength that must be applied to the muscle fiber in order to reach threshold, evoke the action potential and, in turn induce the contraction. The threshold is that intensity (voltage) of stimulus which brings response. The experiment will note

Muscles are responsible for producing movement and maintaining positions in the body. Skeletal muscles, specifically, are formed by one or more muscle fibers that are controlled by a nerve, this is called a motor unit. For muscles to contract, the motor unit must be stimulated, thus allowing the muscle fibers to contract. Through such contraction, our body is able to perform many tasks, whether it is walking, jumping, or simply sitting up. When a muscle contracts, the strength that the motor unit is able to ‘pull’ is known as the summation.

Exercise 2: Skeletal Muscle Physiology: Activity 3: The Effect of Stimulus Frequency on Skeletal Muscle Contraction Lab Report Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. During a single twitch of a skeletal muscle You correctly answered: b. maximal force is never achieved. 2. When a skeletal muscle is repetitively stimulated, twitches can overlap each other and result in a stronger muscle contraction than a stand-alone twitch. This phenomenon is known as You correctly answered: c. wave summation. 3. Wave summation is achieved by You correctly answered: a. increasing the stimulus frequency (the rate of stimulus delivery to the muscle). 4. Wave summation increases the force produced in the muscle.