Transcript Figure 10.17 The Arrangement of Motor Units in a Skeletal Muscle

Figure 10.17 The Arrangement of
Motor Units in a Skeletal Muscle
Figure 10.17
Tension production by skeletal
muscles
• Internal tension generated inside
contracting muscle fibers
• External tension generated in extracellular
fibers
Figure 10.16 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 10.17 The Arrangement of
Motor Units in a Skeletal Muscle
Figure 10.17
Contractions
• 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
Figure 10.18 Isotonic and
Isometric Contractions
Figure 10.18
Figure 10.19 Resistance and Speed
of Contraction
Figure 10.19
•
Muscle Contraction requires
Creatine phosphate
(CP)
releases stored
energy to convert
large
amounts
of
E
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. O2) 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
O2; far less ATP produced
Figure 10.20 Muscle
Metabolism
Figure 10.20
Figure 10.20 Muscle
Metabolism
Figure 10.20
Energy use and level of muscular
activity
• 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)