Factors that influence muscle tension - Sarcomere length and force, understretched and overstretched
• Muscle tension generated through the contraction of muscle cells provides the force necessary for the muscular system to function. • The amount of tension produced depends on several factors: • Sarcomere length Frequency of stimulation • Motor unit size • Recruitment of motor units Sarcomere length and force • The length of the sarcomere determines the degree of overlap between myosin (thick filament) and actin (thin filament). • The more the overlap, the greater the number of crossbridges, which form when myosin heads attach to actin. • The greater the number of crossbridges in the myofibril, the greater the amount of tension and the force of muscle contraction. Sarcomere length - understretched • In an understretched sarcomere the ends Of the actin filaments begin to overlap and hinder each other. • As crossbridge formation decreases, muscle tension declines, and contraction force weakens. Continued shortening of a sarcomere sharply reduces muscle tension and contraction force. Sarcomere length - overstretched • In an overstretched sarcomere the overlap between the myosin and actin filaments is reduced. • Smaller number of crossbridges results in lower muscle tension and weaker contraction. • When there's no overlap at all, crossbridges cannot form and muscle tension drops to zero.
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