indirect and direct stimulation of frog muscle What was the muscle we used, what
ID: 82695 • Letter: I
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indirect and direct stimulation of frog muscle What was the muscle we used, what is the purpose of ringers, how did we indirectly stimulate the muscle, we altered several parameters for stimulation, what were these parameters and how does each parameter alter the contraction of muscle, what is a twitch, what is incomplete tetanus, what is tetanus and why does it occur, what occurs during fatigue, what is a motor unit, what allows force of contraction to increase, what is summation, how did direct stimulation differ from indirectExplanation / Answer
Muscles are categorized in to striated like skeletal and cardiac muscles or unstriated like smooth muscle. These are categorized depending on the alternating dark and light bands or stripes occurring on the muscle. Further muscles are categorized into voluntary muscle (skeletal muscle) or involuntary muscle (cardiac or smooth muscle) depending on the innervations of somatic nervous system. A whole muscle is a muscle of organ which is further classified into muscle fiber or muscle of a cell, myofibril or intracellular structure of muscle, thick and thin bands or cytoskeletal elements of the muscle and muscle proteins such as myosin and actin.
Ringer's solution is the saline which enables the entry of ions like calcium, sodium and potassium into muscles when the muscles are bathed in the solution. This can be useful to study the muscle contraction and relaxation and ion movement into muscles and stimulation of muscle activity by the ions.
The muscle tension is generated within the sarcomere due to cross bridge activity and the resulted sliding of filaments. The sarcomeres are not directly attached to bones but the tension generated by these contractile elements is transmitted to bone via tendons. Tendon is a non-contractile elastic tissue that connects the bone with the muscle. Thus, muscle tension is transmitted to bone by the tightening of this elastic component. The force applied to the bone moves it against the load.
High strength of contraction of skeletal muscle can be changed to generate greater force. There are several means for the generation of great force. These include the recruitment of motor neurons, absence of fatigue, twitch summation, tetanus and muscle hypertrophy.
All muscle fibers forming a bundle called motor unit. For strong contractions to occur several motor units are recruited and stimulated to contract simultaneously and this process is known as motor unit recruitment.
The absence of fatigue contributing to sustained contraction for longer duration. The contractions with greater tension resulting in the two twitches produced from two action potentials summing into a greater tension is known as twitch summation.
Stimulated muscle fiber does not have a chance of relax between the stimuli and result in smooth sustained contraction of maximal strength known as tetanus. Tetanus is 3 – 4 times stronger than a single twitch. Muscle enlargement with the increase in diameter results in hypertrophy which causes powerful contractions.
The twitch summation is accomplished by two factors and they are sustained elevation of cytosolic Ca2+ levels and more time to stretch the series elastic component.
The level of cytosolic Ca2+ is increased by the repetitive release of Ca2+ from the lateral sacs. The repeated excitation of skeletal muscle cell results in inadequate time availability between action potentials to pump all of the Ca2+ released back into the lateral sacs. The sustained elevated cytosolic Ca2+ levels lead to prolonged exposure of myosin cross bridge binding sites for interaction with actin molecules. This generates greater power stroke resulted by twitch summation.
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