Introduction
Force-length curves offer insight into how muscles function. Muscles are made up of fascicles, which are bundles of muscle fibers. Muscle fibers are allowed to shorten during a contraction when myosin moves past actin in sarcomeres. The length of the sarcomeres affects the number of action-myosin cross-bridges, therefore affecting the force output of the muscle. When a sarcomere is very short, the myosin cannot move (as it essentially hits a brick wall), so force output is very low. Additionally, when a sarcomere is very long, there are little-to-no actin-myosin cross-bridges and the force output remains very low. However, when the sarcomere length is somewhere in the middle, the number of actin-myosin cross-bridges increases
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Then, all subjects were plotted on a shared graph. One subject’s protocol was different and had different angles. This data had to be excluded from further analysis due to this. OpenSim was utilized to find the moment arm and muscle lengths at each angle. Rectus femoris and biceps femoris long head were chosen as representative muscles for extension and flexion, respectively. Using this new information, muscle force could be calculated. Force-length curves and scaled force-length curves were formed for the quadriceps and the hamstrings. To provide statistical information, the average force was plotted with error bars to show the standard deviation of each collection …show more content…
The slope and shape looks like an accepted force-length curve; however, it is upside down. This could be due to OpenSim’s coordinate system, because it gave negative moment arms for those muscles, but the Biodex software did not give negative torques. Perhaps if I chose a different representative muscle, instead of the biceps femoris long head, I would have gotten a better plot. The error bars on this plot were smaller. At a muscle length between 0.39 and 0.4 meters, they reach a minimum. This suggests that torque output during flexion is more uniform between subjects, which contradicts the earlier notion that torque output is varied between subjects. Therefore, the quadriceps are varied between subjects whereas the hamstrings aren’t as varied between
In the beginning phases of muscle contraction, a “cocked” motor neuron in the spinal cord is activated to form a neuromuscular junction with each muscle fiber when it begins branching out to each cell. An action potential is passed down the nerve, releasing calcium, which simultaneously stimulates the release of acetylcholine onto the sarcolemma. As long as calcium and ATP are present, the contraction will continue. Acetylcholine then initiates the resting potential’s change under the motor end plate, stimulates the action potential, and passes along both directions on the surface of the muscle fiber. Sodium ions rush into the cell through the open channels to depolarize the sarcolemma. The depolarization spreads. The potassium channels open while the sodium channels close off, which repolarizes the entire cell. The action potential is dispersed throughout the cell through the transverse tubule, causing the sarcoplasmic reticulum to release
James’s biopsy of his right gastrocnemius muscle would have shown a degeneration of the muscle or skeletal fibers due to the lack of dystrophyn. Another microscopic change that would be noticed is the accumulation of white blood cells. White blood cells have a very specific function which is to clear the damaged muscle fibers from the debris. Clearly, due to some of the muscle fibers being damaged other healthy fibers that have not been damaged appear denser. By having damaged muscle fibers, all the work rest upon the healthy fibers making them contract to the fullest due to the fact that the myosin and acting would have to overlap even more to make the muscle work.
The first activity was isolating the gastrocnemius muscle. A cut between the thigh and hip was made so the skin can be pulled down past the lower leg. Then the tendon was cut away from the bone of the heel and one end of the nine-inch string was tied to the tendon. This led to the isolation of the sciatic nerve, found between the hamstring and heel on the lateral side of the thigh. Using fingers, the seams along the quadriceps and hamstring underwent a blunt dissection. In doing so, the glass-dissecting probe was used to free the sciatic nerve embedded in the tissues. A four-inch string was inserted between the nerve and the tissues. Then the transducer was calibrated using a fifty-gram block under the “Frog Muscle” program. Parameter of CAL 1 was changed to zero grams and CAL 2 was changed
Another weakness in the experimental design was that the reliability of the experiment was very low. As each test subject was only tested against each amount of prior exercise once, the impact of random errors is likely very large, which can be seen by the spread of the data on the graph. Although, this was attempted to be rectified by averaging the results of all four test subjects, it does not improve reliability too much. Conclusion: The results of this investigation indicated that a relationship between the amount of prior exercise and muscle fatigue does exist, however the results are also not conclusive enough to speculate on what the relationship is. This means that the hypothesis “If the amount of time spent performing vigorous exercise prior to the set of repetitions increases, then the physical performance (number of repetitions) will decrease” cannot be supported or rejected due to the inconclusive data.
One of the most important muscles in both a mink and a human are those of the arms and shoulders because of their involvement with movement. One of the primal movers of arm abduction along the frontal plane is the deltoid muscle found in both minks and humans. In both species, deltoid muscles allow for the abduction of the humerus. The next two muscles are the biceps brachii and its opposing muscle the triceps brachii. The biceps brachii consists of two heads, which arise from the scapula and join to form a single muscle that ends upon the upper forearm. The most important functions of the biceps brachii are the supination of the forearm and the flexing of the elbow. The triceps brachii on the other hand extends the forearm in both minks and humans and has three heads as opposed to two in its antagonist biceps brachii (Scott). The origin of the triceps brachii is also from the scapula like the biceps brachii. In a mink, the extensor digitorium originates on the lateral epicondyle of the humerus yet in humans it is present in the posterior forearm and is responsible for extending the phalanges, wrist, and elbow in both species. Anothier muscle with similar functions to the extensor digitorium is the flexor carpi ulnaris but instead it is soley responsible for flexin...
When performing manual muscle testing for shoulder flexion and abduction, PTA’s typically place their hand at the wrist verses the mid-extremity because placing their hands at the wrist increases the length of the lever thus testing the muscles ability to resist externally applied force overtime and across the bone-joint lever arm system. Shorter lever arms will provide higher testing scores when compared to using longer lever arms, thus changing the point of force application affects the length of the lever arm and therefore the muscle torque.
...st the sacrolemma will depolarized, thus activation potentials along the T-tubules. This signal will transmit from along the T-tubules to sarcroplasmic reticulum's terminal sacs. Next, sarcoplasmic reticulum will release the calcium into the sarcroplasm leading to the next second event called contraction. The released calcium ions will now bind to troponin. This will cause the inhibition of actin and mysoin interaction to be released. The crossbridge of myosin filaments that are attached to the actin filaments, thus causing tension to be exerted and the muscles will shorten by sliding filament mechanism. The last event is called Relaxation. After the sliding of the filament mechanism, the calcium will be slowly pumped back into the scaroplasmic reticulum. The crossbridges will detach from the filaments. The inhibition of the actin and myosin will go back to normal.
Cardiovascular Activity And How it Influences the body. Introduction: Cardiovascular fitness is a form of aerobic fitness (Neporent and Egan 1997). There are many different ways of evaluating the amount of oxygen used during cardiovascular fitness and one the methods involved is called VO2 Max. VO2 Max is the maximum amount of oxygen that the body can hold.
Kinesiology: The Mechanics & Pathomechanics of Human Movement (Second ed.). Glenside, Pennsylvania: Lippincott Williams & Wilkins. Qiao T, Liu C and Ran F. (2005) The impact of gastrocnemius muscle cell changes in chronic venous insufficiency. Eur J Vasc Endovase Surg 30; 430-436.
Throughout literature countermovement jumps (CMJ) are seen to be higher in contrast to squat jumps (SJ) (Bobbert et al. 1996; Kubo et al. 1999; Bobbert et al. 2005). However present literature regarding the key potential mechanisms behind why greater muscle forces are seen accelerating the body upwards in CMJ in comparison to SJ is somewhat unclear. A CMJ can be defined as a positioning starting upright, beginning the descending motion in advance of the upward motion in contrast to a SJ where the start position is squatted with no preparatory countermovement (Akl 2013). The higher jump heights seen in CMJ in comparison to SJ are apparent even if at the start of propulsion phase the body configuration is identical (Bobbert et al. 1996). In past literature three main mechanisms have looked to provide an explanation for the greater muscle forces seen in CMJ than the SJ. The first plausible theory is that the muscle stretch in CMJ increases the production of force capability of the contractile machinery (Edman et al. 1978; Ettema et al. 1992; Herzog et al. 2003). Secondly the assumption that the muscle fibres are on the descending limb of their force–length relationship at the start of propulsion in the CMJ and SJ, however in CMJ the stretching of a chain of elastic components, they are not as far past optimum length therefore allowing a greater force over the initial phase of their shortening range, with the stretching of sequences of elastic components, this then causes the storage of elastic energy that is then reutilized in the propulsion phase (Ettema et al. 1992). The final explan...
The sarcomere is found in structures called myofibrils which make up skeletal muscle fibres. Within the sarcomere there are various different proteins. One of the most significant, myosin is found in the thick filaments of the sarcomere. Although both cells contain myosin, it is important to highlight that smooth muscle cells contain a much lower percentage of myosin compared to skeletal muscle cells. Despite this, myosin filaments in smooth muscle cells bind to actin filaments in a manner similar to that in skeletal muscle cells; although there are some differences. For instance, myosin filaments in smooth muscle cells are saturated with myosin heads so that myosin can glide over bound actin filaments over longer distances, enabling smooth muscle cells to stretch further, whilst in skeleta...
Myosin is a thick filament which are longer in smooth muscles than in skeletal muscles. (Filatov,
The purpose of this experiment was to gather data on how the amount of time spent active impacts the speed of heart rate in beats per minute. The hypothesis stated that if the amount of time active is lengthened then the speed of the heart rate is expected to rise because when one is active, the cells of the body are using the oxygen quickly. The heart then needs to speed up in order to maintain homeostasis by rapidly providing oxygen to the working cells. The hypothesis is accepted because the data collected supports the initial prediction. There is a relationship between the amount of time spent active and the speed of heart rate: as the amount of time spent active rose, the data displayed that the speed that the heart was beating at had also increased. This relationship is visible in the data since the average resting heart rate was 79 beats per minutes, while the results show that the average heart rate after taking part in 30 seconds of activity had risen to 165 beats per minute, which is a significantly larger amount of beats per minute compared to the resting heart rate. Furthermore, the average heart rates after 10 and 20 seconds of activity were 124 and 152 beats per minute, and both of which are higher than the original average resting heartbeat of 79.
AIM: - the aim of this experiment is to find out what the effects of exercise are on the heart rate. And to record these results in various formats. VARIABLES: - * Type of exercise * Duration of exercise * Intensity of exercise * Stage of respiration
The muscular system is a very important part of the human body. It has many components and functions, and is the source of the body’s movement. There are roughly 650 muscles in the human body and are different types of muscles. Muscles can either be voluntary or involuntary which means controlled or uncontrolled movement. Muscles have many reasons and in this paper you will widen your knowledge of muscles and their functions as well their diseases and how they help maintain the body.