Skeletal Muscle: a Study of Skeletal Muscle Contraction Mechanism in Fogs and the Various Factors Affecting It
Experiment 2: Skeletal Muscle
ABSTRACT
Frog skeletal muscle is used as an animal model to study muscle contraction. The objectives of this experiment is to demonstrate the physiological responses of skeletal muscle to electrical stimuli using frog gastrocnemius, to understand twitch, summation, tetanus and fatigue, to investigate the relationship between initial tension and force of contraction, to explore the differences between human and frog skeletal muscle. The threshold voltage is 0.4V. The minimum voltage required to give a maximal response is 5V. Stimulus voltages and muscle response shows a linear relationship from 0.4V to 5V and reaches plateau at 6V. The optimal initial tension at which maximum force of contraction could be achieved is 45 g. Maximum contraction occurs when maximum number of cross-bridges are formed. The duration of twitch contraction is 233 ms, which is considerably longer than the duration of action potential (1-2 ms). Summation of twitches, subteanus, and complete tetanus occurred at frequency of 5 Hz, 10 Hz and 20 Hz respectively. The duration of muscle fatigue was longer than nerve fatigue during prolonged stimulation at 100 Hz. After addition of d-tubocurarine and the stimulation of the muscle and nerve, full muscle response was seen, but no nerve response was observed because d-tubocurarine blocks the signal pathway by competing with acetylcholine for its nicotinic receptor binding sites. Human muscle had higher threshold voltage than the frog muscle because humans have larger body mass and thus higher muscle mass. However, tetanus and summation of human muscle occur at same frequency as those of the frog muscle.
INTRODUCTION
Skeletal muscles are the engines of the body. They are attached to the bones of the skeleton and so serve to produce movements or exert forces. They are essential for positioning and the movement of the skeleton [1]. They consist of muscle fibers that contain sarcoplasmic reticulum and the t-tubule [1].
ABSTRACT
Frog skeletal muscle is used as an animal model to study muscle contraction. The objectives of this experiment is to demonstrate the physiological responses of skeletal muscle to electrical stimuli using frog gastrocnemius, to understand twitch, summation, tetanus and fatigue, to investigate the relationship between initial tension and force of contraction, to explore the differences between human and frog skeletal muscle. The threshold voltage is 0.4V. The minimum voltage required to give a maximal response is 5V. Stimulus voltages and muscle response shows a linear relationship from 0.4V to 5V and reaches plateau at 6V. The optimal initial tension at which maximum force of contraction could be achieved is 45 g. Maximum contraction occurs when maximum number of cross-bridges are formed. The duration of twitch contraction is 233 ms, which is considerably longer than the duration of action potential (1-2 ms). Summation of twitches, subteanus, and complete tetanus occurred at frequency of 5 Hz, 10 Hz and 20 Hz respectively. The duration of muscle fatigue was longer than nerve fatigue during prolonged stimulation at 100 Hz. After addition of d-tubocurarine and the stimulation of the muscle and nerve, full muscle response was seen, but no nerve response was observed because d-tubocurarine blocks the signal pathway by competing with acetylcholine for its nicotinic receptor binding sites. Human muscle had higher threshold voltage than the frog muscle because humans have larger body mass and thus higher muscle mass. However, tetanus and summation of human muscle occur at same frequency as those of the frog muscle.
INTRODUCTION
Skeletal muscles are the engines of the body. They are attached to the bones of the skeleton and so serve to produce movements or exert forces. They are essential for positioning and the movement of the skeleton [1]. They consist of muscle fibers that contain sarcoplasmic reticulum and the t-tubule [1].