Factors That Affect The Activity Of Contractile Activity

Contractility of ASM requires an increased levels of intracellular Ca2+. When surface receptors are not activated, Ca2+ levels are low. Upon activation of these cell surface receptors by contractile agonists e.g. acetylcholine, serotonin and histamine, intracellular Ca2+ increases causing a contraction (9). Smooth muscle cell contraction is controlled by both receptor and mechanical activation of proteins actin and myosin and also changes to membrane potential.

As the trials progressed, the strength of the muscles decreased as well because of the experienced muscle fatigue due to the lactate threshold. In

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.

Creatine phosphate has been heavily experimented upon to show that it is an important effector towards muscle activity. When creatine phosphate is present in a solution containing muscle fibers without the presence of ATP, it serves as the energy supplier due to the fact that it absorbs bound adenine nucleotide, which is firmly linked to the contractile elements on muscle fibers (Bozler, 1953). Even in low concentrations this nucleotide can be considered an energy transfer mechanism, for it takes full advantage of the creatine phosphates energy supply, thus acting as a substrate for the enzymatic activity of the contractile elements of a muscle group. Consumption of this nucleotide leads to an increase in the strength of contraction. Creatine phosphate also speeds up rate of relaxation of muscles, for it induces the relaxing effect of ATP (Bozler, 1953). Thus, this research suggests that creatine phosphate is directly linked to instigate muscle contractibility.

Next, to determine if contraction via the EMC pathway requires extracellular or intracellular calcium, the second type of stimulus was used and the tissue was stimulated using calcium free K+-depolarising solution. The bathing solution in this experiment was calcium free solution to make sure all extracellular calcium was eliminated, as without calcium, the EMC pathway is expected to produce no response.

Abstract: In this experiment the measurements of skeletal muscle fibers of the rabbit are in millimeters. The average length for the three muscle fibers after adding the solution A which contained only 0.25% ATP in distilled water was 20 mm. The average length for the three muscle fibers after adding the solution C which contained 0.5M KCl and 0.001M MgCl2 in distilled water was 1.77 mm and the average length for the three muscle fibers after adding the solution B which contained 0.25 % ATP and 0.5 M KCl with 0.001 M Mgcl2 in water was 1.77 mm.

An increase in calcium inside muscle cells activates processes that generate heat and production of excess acid, leading to a continual increase in body temperature and then acidosis.

During relaxation calcium is pumped back into the sarcoplasmic reticulum, troponin loses its calcium and tropomyosin reverts. When this action occurs it blocks mechanism of muscle regulation.

The muscle spindles and Golgi tendon organ are fundamental to the control of muscle length and tone. Any disturbance in the activity of these receptors may occur through shortened muscle length, intense work exercise and exercise to fatigue. This will likely result in an increase of motor neuron activity and motor unit recruitment. The relaxation phase of a muscle contraction is prolonged in a fatigued muscle, raising the likelihood of fused summation of action potentials if motor neuron activity muscle spindle and motor neuron activity by reflex inhabitation and afferent stimulation (Bentley, S, 1996). It has been documented that fatigue increases the afferent activity of the muscle spindle and decreases afferent activity of the Golgi tendon organ which, then may result in an increased alpha motor neuron activity. The uncontrolled firing of neurons on the muscle and the reduced relaxation of the muscle fibers leads to cramps (Schwellnus MP, 2010).

Muscle fatigue is the process of exhaustion or strength lost, as well as muscular endurance that corresponds with the building up of lactic acid in the muscles (Medical Dictionary) Throughout the lab it was discovered that the greater the number of muscles in the body that are used, the more fatigue builds up, and it becomes difficult to use those muscles. According to table 1.2 and 1.3, there was a decrease in the number of squeezes of a clothespin that were completed in 30 seconds for each of the 10 trials. As the number of trials were increased it became difficult to press the clothes pin quickly and efficiently, causing the fingers’ pace to slow down. The first couple of trials were easily completed without muscle soreness since the

Potassium is a necessary intracellular ion, found in each cell membrane, playing a vital role in the normal functioning of nerve and muscle cells. It is crucial for proper fluid balance in the body by countering the effect of sodium and creates an electrical charge across the cell membrane. This is important as it allows nerves to conduct electrical impulses to communicate between muscles and cells to contract. A majority is found inside muscle tissue, and the balance between sodium and potassium ions is crucial to maintain an electrical gradient which works to transport substances in/out the cell and transmit nerve signals which consequently trigger muscle contractions.

The findings of this experiment reinforced the hypothesis that the resting membrane potential is most influenced by the ion potassium. We were able to deduce this through the collection of a multitude of intracellular and extracellular recordings, such as the one shown below in Figure 1. This shows how this experiment was able to record every single resting membrane potential in all three different muscle groups under all six solutions.

supply more oxygenated blood in time to assist with the activity the muscle is undertaking. If a

muscle fiber. The change in membrane potential causes a decrease in the release of calcium from

twitch muscles. Fast twitch muscles have a fast form of myosin ATP and are very