chapter 6 contraction of skeletal muscle dr. marko ljubković department of physiology
TRANSCRIPT
Chapter 6
Contraction of Skeletal Muscle
Dr. Marko LjubkovićDepartment of Physiology
Anatomy of Skeletal Muscle
• Muscle fibers
• Myofibrils
• Sarcomeres
Sarcomere
Myofibrils
SR
Anatomy of Skeletal Muscle
Actin and Myosin Filaments
Cross-bridge Cycle
Muscle Length-Force Relationship
Velocity-Load Relationship
Determined by isotonic contraction
Sources of Energy for Contraction1. ATP pool
2. Creatine phosphate
3. Carbohydrates
• Glycolysis
• Oxidative phosphorylation
4. Fatty acids
• β-oxidation
Oxygen debt• Strenuous ex. (mostly fast
motor units)• Endurance ex. (slow units)
Fatigue• Accumulation of lactic acid
Types of Muscle Fibers
1. Fast twitch fibers• Thicker muscle fibers and nerves• Extensive SR• Abundance of glycolitic enzymes• Lower mitochondrial content• Different myosin isoform
2. Slow twitch fibers3. Both types found in individual muscle
Mechanics of Muscle Contraction
1. Motor unit
• α-motor neuron + muscle fibers
• Small (100 to 500 fibers, slow twitch) and Large (1000 to 2000 fibers, fast twitch)
2. Recruitment
• Slow twitch units recruited first
• Spatial summation
• Temporal summation (frequency depends on muscle type)
Muscle Growth