Figure Figure The Arrangement of Motor Units in a Skeletal Muscle

Internal tension generated inside contracting muscle fibers External tension generated in extracellular fibers Tension production by skeletal muscles

Figure Internal and External Tension Figure 10.16

Motor units –All the muscle fibers innervated by one neuron –Precise control of movement determined by number and size of motor unit Muscle tone –Stabilizes bones and joints

Figure Figure The Arrangement of Motor Units in a Skeletal Muscle

Isometric –Tension rises, length of muscle remains constant Isotonic Tension rises, length of muscle changes Resistance and speed of contraction inversely related Return to resting lengths due to elastic components, contraction of opposing muscle groups, gravity Contractions

Figure Isotonic and Isometric Contractions Figure 10.18

Figure Figure Resistance and Speed of Contraction

Creatine phosphate (CP) releases stored energy to convert ADP to ATP –CP made creatine with excess ATPs –Returns energy to ATP via enzyme creatine phosphokinase (CPK); excess in blood with muscle damage Aerobic metabolism (req. O 2 ) provides most ATP needed for contraction Glycolysis in cytoplasm; oxidative phosphorylation in mitochondria At peak activity, anaerobic glycolysis needed to generate ATP Fermentation- lactate from pyruvate; temporarily maintains glycolysis without O 2 ; far less ATP produced Muscle Contraction requires large amounts of E

Figure Muscle Metabolism Figure 10.20

Figure Muscle Metabolism Figure 10.20

Energy production and use patterns mirror muscle activity Fatigued muscle no longer contracts –Build up of lactic acid –Exhaustion of energy resources lack of ATP, CP, pH drop (lactate) Energy use and level of muscular activity