Anatomy and Physiology: Sketetal Muscle Mechanics and Metablolism
Anatomy and Physiology: Sketetal Muscle Mechanics and Metablolism ANPS 019
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This 3 page Class Notes was uploaded by Olivia may on Tuesday October 18, 2016. The Class Notes belongs to ANPS 019 at University of Vermont taught by Sean Flynn in Fall 2016. Since its upload, it has received 4 views.
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Date Created: 10/18/16
Lecture objectives 16 1. Describe and identify the components of the motor unit A single motor neuron + fibers it controls = a motor unit 2. Describe the components of a muscle twitch Muscle twitch - a motor unit's response to a single action potential from the motor neuron Latent Period - first few milliseconds, excitation - contraction coupling starts, cross bridges formed but no measurable shortening Contraction Period - 10-100 ms, cross bridges active, reach peak of muscle tension, muscles may shorten Relaxation Period - 10-100 ms, initiated by Ca2+ re entry into the SR, decreased number of active cross bridges, muscle tension decreased to zero, muscle returns to initial length 3. What is muscle tension? How is the difference from muscle tone? Muscle tension - force exerted by a contracting skeletal muscle on an object, muscle does not always shorten Muscle tone - relaxed muscles are always slightly contracted, generated by involuntary neural stimulation, involved in maintenance of posture and joint stabilization, NOT movement 4. Describe why muscle responses are graded and how frequency and strength of stimulation modulate that response Graded response - contract to varying degrees based on load. Same muscle that lift a pencil lift a 40 lb weight. Frequency - Wave summation - (low stimulus frequency) another stimulus is added before muscle relaxes completely, which increases tension b/c not al Ca2+ is removed which mean more active cross bridges - (high stimulus frequency) NOT a physiological event - muscle reached max tension then fails and tension drops to zero - tetanus events Strength of Stimulation - Sub-threshold stimulus - no observable contraction Threshold stimulus - the stimulus at which the first observable contraction occurs Size principal - small, more excitable fibers are recruited first, large, less excitable fibers are recruited only for powerful contractions. Individual motor units may be recruited asynchronously to delay fatigue 5. Compare and contrast isometric and isotonic contraction Isometric - “same measure”, the load exceeds muscle peak, contracting is not visible but there is tension. Isotonic - “same tension”, muscle forms enough tension to over some load and contract. Tension remains constant for the rest of the contraction. Concentric - muscle shortens as it does work Eccentric - muscle lengthens to generate force 6. How do muscle cell use and generate energy Hydrolysis of ATP resulting and ADP and a phosphate 7. What are the 3 metabolic pathways used by muscles to generate ATP At rest muscle store about 4-6 seconds of ATP for activity Immediate supply via direct phosphorylation - coupled reaction of creatine phosphate and ADP ---> creatine kinase-----> creatine and ATP - does NOT require oxygen - about 15 seconds of activity Short term supply via anaerobic cellular respiration - glucose from oxygen stored in blood supply, glycolysis in cytosol, glucose converted into two pyruvate molecules releasing 2 ATP molecules, lactic acid is then released into the blood due to compression of blood vessels and resulting oxygen deficiency Long term supply via aerobic cellular respiration - occurs within mitochondria, REQUIRES OXYGEN, pyruvate oxidizes to carbon dioxide, transfer of chemical bond energy to NADH and FADH2, energy used to generate ATP by oxidative phostoplation, 32 net ATP produced per glucose, after 30 minutes free fatty acids are also used for aerobic respiration and are the preferential fuel molecules for most skeletal muscle 8. How does exercise and aging affect muscle cells?
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