tailieunhanh - Lecture Human anatomy and physiology - Chapter 9: Muscles and muscle tissue (part c)

The main contents of this chapter include all of the following: Force of muscle contraction, avelocity and duration of contraction, muscle fiber type, effects of exercise, effects of resistance exercise, the overload principle, smooth muscle, peristalsis, microscopic structure, innervation of smooth muscle,.and other contents. | 9 Muscles and Muscle Tissue: Part C Force of Muscle Contraction The force of contraction is affected by: Number of muscle fibers stimulated (recruitment) Relative size of the fibers - hypertrophy of cells increases strength Force of Muscle Contraction The force of contraction is affected by: Frequency of stimulation - frequency allows time for more effective transfer of tension to noncontractile components Length-tension relationship - muscles contract most strongly when muscle fibers are 80–120% of their normal resting length Figure Large number of muscle fibers activated Contractile force High frequency of stimulation Large muscle fibers Muscle and sarcomere stretched to slightly over 100% of resting length Figure Sarcomeres greatly shortened Sarcomeres at resting length Sarcomeres excessively stretched 170% Optimal sarcomere operating length (80%–120% of resting length) 100% 75% Velocity and Duration of Contraction Influenced by: Muscle fiber type Load Recruitment Muscle Fiber Type Classified according to two characteristics: Speed of contraction: slow or fast, according to: Speed at which myosin ATPases split ATP Pattern of electrical activity of the motor neurons Muscle Fiber Type Metabolic pathways for ATP synthesis: Oxidative fibers—use aerobic pathways Glycolytic fibers—use anaerobic glycolysis Muscle Fiber Type Three types: Slow oxidative fibers Fast oxidative fibers Fast glycolytic fibers Table Figure Predominance of fast glycolytic (fatigable) fibers Predominance of slow oxidative (fatigue-resistant) fibers Small load Contractile velocity Contractile duration Effects of Exercise Aerobic (endurance) exercise: Leads to increased: Muscle capillaries Number of mitochondria Myoglobin synthesis Results in greater endurance, strength, and resistance to fatigue May convert fast glycolytic fibers into fast oxidative fibers Effects of Resistance Exercise Resistance exercise (typically anaerobic) results in: Muscle hypertrophy (due to increase in | 9 Muscles and Muscle Tissue: Part C Force of Muscle Contraction The force of contraction is affected by: Number of muscle fibers stimulated (recruitment) Relative size of the fibers - hypertrophy of cells increases strength Force of Muscle Contraction The force of contraction is affected by: Frequency of stimulation - frequency allows time for more effective transfer of tension to noncontractile components Length-tension relationship - muscles contract most strongly when muscle fibers are 80–120% of their normal resting length Figure Large number of muscle fibers activated Contractile force High frequency of stimulation Large muscle fibers Muscle and sarcomere stretched to slightly over 100% of resting length Figure Sarcomeres greatly shortened Sarcomeres at resting length Sarcomeres excessively stretched 170% Optimal sarcomere operating length (80%–120% of resting length) 100% 75% Velocity and Duration of Contraction Influenced by: Muscle fiber type Load Recruitment Muscle

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