Skeletal Muscle Contraction Report

Nerves are responsible for the controlling the contraction of muscles, determining the number and the sequence and force of muscle contractions (Muscle Fatigue, 2015). The movements that are required for a force far below what a muscle is able to generate and with the exception of pathology nervous fatigue is seldom an issue. For extremely powerful contractions that are close to the upper limit of a muscle’s ability to generate force, nervous fatigue can be limiting factor in untrained individuals.

The twitch tension of fast-contracting fibres (white muscle) is increased by adrenaline, particularly if the muscle is fatigued. Whereas the twitch of slow (red) muscle is reduced. These effects depend on an action on the contractile proteins, rather than on the membrane and the mechanism is poorly understood. In humans, adrenaline and other b2-agonists cause a marked tremor: shakiness that accompanies fear, excitement or the excessive use of b2-agonists (example: salbutamol) in the treatment of asthma examples of this. This results from an increase in muscle spindle discharge, coupled with an effect on the contraction kinetics of the fibres, these effects combining to produce an instability in the reflex control of muscle length. Beta-receptor antagonists are sometimes used to control pathological tremor. The b2-agonists also cause long-term changes in the expression of the sarcoplasmic reticular proteins that can control contraction of skeletal

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

As discussed in paper one, readers can see the complexity that lies behind muscle fibers and the contractile units that make up each muscle cell. At the normal physiology level, muscle fibers exist as complex bundles of small muscle filaments. These filaments, known as actin and myosin bind in such a way that allows for sarcomere contraction. In assistance with calcium flowing into muscle cells, proteins known as tropomyosin and troponin ultimately allow “cross bridging” to occur. Throughout the body three types of muscle fibers exist, these types of fibers are slow oxidative, fast oxidative and fast glycolytic. Activation or recruitment of these fibers varies from person to person depending on the muscle specificity needed to perform a given contraction. In other words the innervation of each fiber depends solely on the muscle needed to engage in a specific exercise. By first knowing the anatomy behind a muscle cell one can then have a better understanding of the effects training has on muscle cell hypertrophy.

Effects of Varying Lengths of Rana Pipiens Gastrocnemius on Tetanic Contraction Joshua Porter, Sofia Tuttle, Yoniko Washington TA: Ryan Hoffman Abstract Muscles play an essential role in vertebrate life from maintaining posture and locomotion to controlling the heart. Better understanding them is essential to better understanding life processes. (2) In this experiment, the effects of muscle length on the tetanic contraction tension of the gastrocnemius muscle of a rana pipiens were observed.

Skeletal muscles rarely work by themselves to achieve movements in the body. More often they work in groups to produce precise movements. The muscle that produces any particular movement of the body is known as an agonist or prime mover. The agonist always pairs with an antagonist muscle that produces the opposite effect on the same bones. For example, the biceps brachii muscle flexes the arm at the elbow. As the antagonist for this motion, the triceps brachii muscle extends the arm at the elbow. When the triceps is extending the arm, the biceps would be considered the antagonist.

Participants were tested concentrically at 60% in a seated position with the hips and knees in 90 degrees of flexion and the remainder of the body firmly strapped to the seat of the dynamometer. Before tests had commenced, participants went through a series of warm ups consisting of repetitions at 50%, 75% and 100% intensity. The participants took 1 minute of rest, the participants then completed 3 separate trials at 100% intensity and the peak of these 3 trials were then averaged. Determination of muscle volume was done by a 1.5-T Signa LX magnetic resonance imaging device. While laying supine the scan measured both thighs on the femoral head to the tibiofemoral joint. The muscle volume was determined by measuring muscle cross-sectional area

As the interaction within a single muscle group improves, the motor neurons connection with the individual muscle fibres it innervates is strengthened. The body also becomes better at recruiting motor units and muscle fibres to produce force.

For contraction to occur it is necessary to stimulate the muscle in the form of an impulse (action potential) from the motor neuron. one motor neuron does not stimulate the entire muscle, but only a few muscle fibers in the muscles. The individual motor neuron plus the muscle fibers that it stimulates is called the motor. The end plate of the motor (also known as the neuromuscular junction) is a mix of axons of motor

The length of the biceps muscle changes with the angle. Muscle has a minimum length to which it can be contracted and a maximum length to which it can be stretched and still function. At these two extremes, the force the muscle can exert is much smaller. At some point in between, the muscle produces its maximum force. If the biceps pulls vertically (which is an approximation), the angle of the forearm does not affect the force required; but it does affect the length of the biceps muscle, which in turn affects the ability of the muscle to provide the needed

First Muscles perform three types of contractions: concentric, eccentric, and isometric. When executing a strength exercise, all three of the muscle contractions are involved. As you perform a movement, the main muscles undergo a concentric contraction while the opposite muscles undergo an eccentric contraction. The adjacent parts of the body that are not in use are stabilized via the isometric contraction.

Without the skeletal muscle in our body, we would be stick people; we would have no movement. Almost all of the movement in our body is a result of muscle contraction. Did you know that the skeletal muscle makes up 40% of someone’s body weight, and it forms more than 600 muscles. The muscles allow us to frown, laugh, smile and express many other emotions. But, the most important functions of the muscular system are movement, posture, joint stability and heat production. There are also three major different types of muscle in the body: skeletal, smooth, and cardiac. They all play an important role in maintaining homeostasis.

In the first experiment, as muscle force increases as induced by the subject, it is expected that the EMG activity will elevate likewise due to the directly proportional relationship between contraction strength and the muscle’s amount of electrical impulses. Additionally, it is expected that resistance to fatigue will increase with greater forearm circumference due to the greater amount of fatigue-resistant slow oxidative fibers. In the third section of this lab, it is anticipated that as path length of a particular reflex arc (in this case, the Achilles tendon reflex) increases, the overall conduction velocity will decrease due to the increased reflex time necessary for the impulse to be conducted up and down longer neurons.

In order for us to move, our bodies utilize its muscles to create movement. Muscles help with maintaining body temperature, supporting of soft tissue and skeletal movement. To do this, muscles must be able to contract during each movement. This lab session was completed in order for us to have a greater understanding of how muscles function and to find the relationship between muscle length and force. To better understand what events occur during muscle contraction, an electromyogram (EMG) was used to record the electrical activity of contracted forearm flexors at different angles of the wrist.

The muscular system is fundamental to human life, without the skeletal muscles mobility and balance would be impeded. The purpose of this lab is to study the physiological properties of the skeletal muscle by isolating the gastrocnemius of a frog and running it through a series of tests. These tests will help us identify the minimum and maximum strength of stimulation (threshold and plateau values) that will evoke a muscle twitch. The force generated by muscles is dependent on the total number of muscle fibers, the number of activated fibers also depend on frequency and stimulation.