Skeletal Muscle Contraction And Relaxation Is Vital For

Skeletal muscle contraction and relaxation is vital for voluntary body movements to occur. Skeletal muscles contract when myofibrils composed of actin and myosin slide past each other, which contracts the muscle by altering its length. The gastrocnemius muscle in Rana pipiens, which is attached to the sciatic nerve, can be stimulated to find threshold and maximal stimulus voltage. Once threshold is reached, contraction amplitude increases with stimulus voltage until the maximal voltage is reached, at which point it levels off. Altering the interstimulus interval can induce twitch summation in the gastrocnemius, leading to one combined contraction with a high amplitude. Increased stimulus frequency can be used to induce a tetanic†¦show more content†¦Twitches are the resulting contraction from the firing of an AP in muscles. Twitches are much longer than the APs themselves. Twitch recruitment uses external stimuli to determine the threshold and maximal voltages of nerves and muscles. Stimuli below the threshold voltage, or the minimum stimulus strength required to elicit an action potential, will not cause a muscle to twitch. Once threshold potential is determined, increased stimulus voltage will increase the contraction amplitude of the twitch until the maximal stimulus is reached. The twitch will not significantly increase in strength for any voltage above maximal. This is because at maximal stimulus voltage all motor units have already been recruited to contract. The gastrocnemius muscle has a far higher threshold and maximal voltage that the sciatic nerve due to its size and the number of motor units present in the gastrocnemius. Along with increasing stimulus voltage, contraction amplitude can also be increased through twitch summation. Twitch summation occurs when a muscle is stimulated twice in quick succession, so that the second twitch occurs before the first twitch has relaxed. The twitches then combine to form a stronger muscle contraction. T his process is made possible by the temporal relationship between a muscle’s AP and the resulting twitch, which is far longer in duration than the 1 ms AP that causes it. Due to the nature of skeletal muscle contraction, the length-tension relationship inShow MoreRelatedThe Body s First Line Of Defense And Protection1254 Words   |  6 Pagesand nightly bases. Starting from the outside and working inwards this paper will give you a basic rundown of how each system works. Then talk about how that system works with the other systems within the body. The eleven systems are; integumentary, skeletal, muscular, cardiovascular, endocrine, nervous, respiratory, lymphatic/immune, urinary, gastrointestinal, and reproductive. The integumentary system is the body’s first line of defense and protection. This is your skin, and it is the main part ofRead MoreUnit 5769 Words   |  4 PagesP2: Outline the four main tissue types such as Epithelial, connective, muscle, nervous. 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