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BIOL 103 (103)
Chapter 43


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BIOL 103
Peter T Boag

Jan/27/11 44.4 Skeletal Muscle Function - Skeletal muscle has a variety of functions – locomotion, stretching, chewing, breathing, maintaining balance. - Muscle fibres are classified based on their rates of shortening and the way they produce ATP for contraction. Skeletal Muscle Fibres are adapted for Different Types of Movement - Fast fibres contain myosin with high ATPase activity and is 4x faster at cross-bridge cycling than slow fibres, but the maximal force produced is the same. - Slow fibres contain myosin with low ATPase activity. - Oxidative fibres are fibres with numerous mitochondria and have a high capacity for oxidative phosphorylation, so they rely on many small blood vessels to deliver oxygen. - They can also contain myoglobin, an oxygen-binding protein which provides an intracellular reservoir of oxygen, which gives these fibres a dark red colour. o Oxidative fibres are often called red muscle fibres. - Glycolytic fibres have few mitochondria but possess a high concentration of glycolytic enzymes and large stores of glycogen. They use very little oxygen, myoglobin and is surrounded by few blood vessels, earning them the name ‘white muscle fibres’. - There are 3 types of skeletal muscle: 1. Slow-oxidative fibres (red muscle) - Low ATPase activity but can make large amounts of ATP due to lots of mitochondria. - Used for prolonged, endurance activity. o Ex. Flight, long-distance swimming, maintenance of posture 2. Fast-oxidative fibres - High ATPase activity and can make lots of ATP. - For prolonged, long-term activity like the slow-oxidative fibres – the difference is this fibre is for rapid activities. o Ex. Rapid trilling sounds of throat muscles of birds, clicking sounds of rattlesnake’s tail. 3. Fast-glycolytic fibres - High myosin ATPase activity, but no ATP production since source is glycolysis. - Used for rapid, intense actions because they fatigue rapidly. o Ex. Sprinting, cat pouncing on prey. - Depending on the actions you’re performing, motor nerve inputs can be adjusted to stimulate different ratios of fibre types. CH 43: NEUROSCIENCE- SENSORY SYSTEMS - A sense is a system that consists of sensory cells that respond to a specific type of chemical or
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