Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Essentials of Human Anatomy & Physiology Chapter 8 The Muscular System Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Function of Muscles Produce movement Maintain posture / Stabilize joints Regulation of body temperature / Generate heat Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Connective Tissue Wrappings of Skeletal Muscle Epimysium – covers the entire skeletal muscle Figure 6.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Connective Tissue Wrappings of Skeletal Muscle Perimysium – around a fascicle (bundle of muscle fibers) Endomysium – around single muscle fiber (individual muscle cell Figure 6.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle Myofibril Bundles of myofilaments Myofibrils give skeletal muscle their striated appearance Figure 6.3b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle Sarcomere = Contractile unit of a muscle fiber Thick filaments = Composed of the protein myosin Thin filaments = Composed of the protein actin Figure 6.3c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Muscle Contraction – Motor Units Skeletal muscles must be stimulated by a nerve to contract (motor neuron) Motor unit One neuron Muscle fibers stimulated by that neuron Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.4a Muscle Contraction - Synapse Neuromuscular junctions – site of nerve and muscle connection Neurotransmitters (Acetylcholine) are released upon arrival of a nerve impulse Triggers muscle contraction upon diffusing across the synapse Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.5b The Sliding Filament Theory of Muscle Contraction Figure 6.7 The Sliding Filament Theory of Muscle Contraction This continued action causes a sliding of the myosin along the actin The result is that the muscle is shortened (contracted) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.7 Principles of Muscle Contraction Threshold Stimulus The minimal strength of a stimulus required to cause muscle contraction All or None Law If a threshold stimulus is met a skeletal muscle fiber will contract to its fullest extent (or not all). Recruitment Signifies an increase in motor units activating due to varying levels of stimulation Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Muscle Response to Stimuli Muscle force depends upon the number of fibers (motor units) stimulated More fibers contracting results in greater muscle tension (Strength) Less fibers contracting results in decreased muscle tension (Strength) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Energy for Muscle Contraction Initially, muscles use available Adenosine Triphosphate (ATP) for energy Bonds of ATP are broken to release energy Only 4-6 seconds worth of ATP is stored by muscles After this initial time, other pathways must be utilized to produce ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Energy for Muscle Contraction • Creatine Phosphate Muscle cells contain a high energy molecule called creatine phosphate (CP) After ATP is depleted, ADP is left CP transfers energy to ADP in the transfer of a P, to regenerate ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.10a Energy for Muscle Contraction Anaerobic Respiration Reaction that breaks down glucose without oxygen Glucose is broken down to pyruvic acid to produce some ATP Pyruvic acid is converted to lactic acid Lactic acid produces muscle soreness and cramping Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.10b Energy for Muscle Contraction Aerobic Respiration Series of metabolic pathways that occur in the mitochondria Glucose is broken down to carbon dioxide, water and ATP This is a slower reaction that requires continuous oxygen Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.10c Muscle Fatigue Muscular Fatigue – Lack of production of ATP to sustain muscle contraction Synaptic Fatigue – Lack of production of Acetylcholine to pass across the synapse Psychological Fatigue – neuromuscular system is functional, mind “gives up”. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings