Muscles: Troponin Interaction Between Myosin And T

This activity is the critical driving force of muscle contraction. The stream of action potentials along the muscle fiber surface is terminated as Acetylcholine at the neuromuscular junction is broken down by acetyl cholinesterase. The release of Calcium ions is ceased. The action of the myosin molecule heads is obstructed because of the change in the configuration of troponin and tropomyosin due to the absence of calcium ions. This will eventually cause the contraction to be ceased. Together with these physical processes, an external stretching force such as gravity pulls the muscle back to its normal length.

-Sarcoplasmic Reticulum (SR) then releases Calcium which binds to troponin in the thin filament, exposing myosin-binding sites;

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

How is contraction ended? Ach is released and binds to receptors on the motor end plate, then an action potential is produced which releases Ca+. The Ca+ binds to troponin, then myosin binds to actin to form crossbridges. The myosin pulls the actin then releases from actin and ADP is bound to the myosin.

For muscle to contract, actin and myosin filaments need to slide past each other, causing the sarcomere to shorten in length . Each myosin filament has a protruding bulbous head, which can bind with the binding sites on the

The power stroke is responsible for the contraction of the muscle and force generation. ATP binding to the myosin head detaches the myosin head from the actin filament and allows the cycle to repeat. The coordinated contraction and relaxation of many muscles in an antagonistic fashion is the basis for the kinematics of any movement.

ith the myosin have been activated by the ATP, they will bind the action binding site.

Myofibrils are made up of long proteins that include myosin, titin, and actin while other proteins bind them together. These proteins are arranged into thin and thick filaments that are repetitive along the myofibril in sectors known as sarcomeres. The sliding of actin and myosin filaments along each other is when the muscle is contracting. Dark A-bands and light I-bands reappear along myofibrils. The alignment of myofibrils causes an appearance of the cell to look banded or striated. A myofibril is made up of lots of sarcomeres. As the sarcomeres contract individually the muscle cells and myofibrils shorten in length. The longitudinal section of skeletal muscle exhibits a unique pattern of alternating light and dark bands. The dark staining, A-bands possess a pale region in the middle called the H-zone. In the middle of the H-zone the M-line is found, that displays filamentous structures that can join the thick filaments. The light-staining bands also known as I-bands are divided by thin Z-line. These striated patterns appear because of the presence of myofibrils in the sarcoplasm (IUPUI, 2016).

(Table 1) ATP alone causes myosin to break the cross-bridge and allow the myosin to reattach to the actin causing a muscle contraction, since the solution we used had ATP; I believed that that was enough to cause the fiber contraction. I thought that we had done our experiment in correctly because there was no muscle contraction. I believed that it was due to the amount of solution we added to the fiber. We re did the experiment and added four drops of the solution but there was no muscle contraction as

Heart contraction is produced by stretching of sarcomere units, which produces strokes between myosin head and actin monomers located in the thin filament of sarcomere (Robinson, Dong et al. 2004). Changes in the resting tension of heart muscle affect the range of heart contraction. The heart has the capacity to adjust its contraction force as result of variations in ventricular filling (end-diastole), this effect is known as the Frank–Starling Law (Sequeira and van der Velden 2015). An increased systolic contraction is the results of the ventricle stretching due to greater end-diastolic volume happens (Schneider, Shimayoshi et al. 2006). However,

The sarcomere is the smallest unit of muscle fiber and linked end-to-end within a muscle fiber, which is located between two Z lines and is approximately 2.5 μm long (Toldrá, 2002). The overlapping arrangement of myofilaments results in dark (A) and light (I) bands will cause the striated appearance. The A band is known as area where the actin and myosin overlap. When the area in the A band contains no thin filaments, it will called as H zone, while I band is the region which contains no thick filaments (Feiner, 2006). I bands are bisected by Z-lines which results in dark lines, while A bands bisected by M-lines (Toldrá, 2002). Actin and myosin are connected to the Z line and M line,

There are several steps that are needed to complete muscle contraction. First a neuron action potential arrives at the end of the motor neuron. Acetylcholine (ACh) is later released from the axon to receptors, which is located on the sarcolemma. The sarcolemma is stimulated and a muscle impulse travels over the surface of the muscle fiber and deep into the fiber through the transverse tubules and reaches the sarcoplasmic reticulum

Muscle myopathy is a disease in which the skeletal muscle in human body weakens and difficult to move (Carnell et al., 2012). This disease can also affect the smooth muscle in respiratory tract that leads to shortage in oxygen and carbon dioxide accumulation in blood. This disease is caused by the mutation of ATP-binding activity of actin filaments. Therefore, muscle contraction cannot occur, being that ATP is essential for the muscle to contract. There is no effective cure for this disease (NINDS, 2015). However, some treatments can be done to overcome the weakness of the muscle. Treatment for this disease is based on the muscle condition of the patient. Some physical therapy and using brace as a support of the muscle can help the patient who

form of myosin ATP and are not very good at delivering calcium to the muscle

Both of these muscles expand and contract as they have complex structures so it is essential how they do this. The cardiac muscle needs the contractions to occur in order to pump blood out of the atria and into the ventricles and round the circulatory system so the structure of this muscle shows the systole of the heart. The contractions of the skeletal muscle also depend on its structure. The binding and releasing of two strands of sarcomere is how the repeated pattern of contractions occurs. ATP is used to prepare myosin for binding to allow the contractions to happen. The skeletal and cardiac muscle also both has elasticity. The elasticity is used to restore the muscles back to their original lengths which enable them to resume back to their original length once they have contracted and been stretched.