Ch12 - CHAPTER 12 Muscle Physiology K Wells VPHY3100...

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CHAPTER 12: Muscle Physiology K. Wells VPHY3100: Elements of Physiology Dept. Physiology & Pharmacology College Vet. Med.
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Wells/VPHY3100 Lecture Outline Types of muscle cells How skeletal muscle looks How skeletal muscle works Whole-muscle contraction Types of motor units Neural control of skeletal muscle
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Wells/VPHY3100 Muscles All muscle types Contraction occurs by sliding of actin & myosin filaments Excitation/contraction coupling relies on increases in intracellular calcium Skeletal Muscle Sarcomere is the smallest contractile unit; striated (striped) appearance Control by somatic motor neurons Cardiac Muscle Sarcomere is the smallest contractile unit; striated (striped) appearance Pacemaker cells: automatic rhythmic action potentials & contractions Regulation of strength & frequency of contraction by autonomic motor neurons Smooth Muscle No sarcomeres; no striated appearance Control by autonomic motor neurons
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Wells/VPHY3100 Muscle Types
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Wells/VPHY3100 Lecture Outline Types of muscle cells How skeletal muscle looks How skeletal muscle works Whole-muscle contraction Types of motor units Neural control of skeletal muscle
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Wells/VPHY3100 SKELETAL MUSCLE MUSCLE = bundle of fasciculi FASCICULUS = bundle of muscle fibers MUSCLE FIBER or MYOFIBER = muscle cell MYOFIBRIL = serially- repeating sarcomeres (a single muscle cell contains many myofibrils) SARCOMERE = smallest contractile unit of muscle cell Organization of muscle tissue
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The skeletal muscle cell SARCOLEMMA = plasma membrane of a muscle cell SARCOPLASM = cytoplasm of a muscle cell SARCOPLASMIC RETICULUM (SR) = specialized endoplasmic reticulum of a muscle cell Muscle cells are multi-nucleated Muscle cells appear striated due to dark & light banding pattern of sarcomeres
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Wells/VPHY3100 Lecture Outline Types of muscle cells How skeletal muscle looks How skeletal muscle works The motor unit The neuromuscular junction Excitation/contraction coupling Sarcomere structure & the sliding filament model of contraction Whole-muscle contraction Types of motor units Neural control of skeletal muscle
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Wells/VPHY3100 The Motor Unit A motor unit is comprised of a single motor neuron and all of the muscle fibers (cells) it innervates A typical motor neuron innervates 100 to 1,000 muscle cells One muscle cell is typically innervated by a single motor neuron A muscle is comprised of many motor units All muscle fibers in the same motor unit are of the same type (characterized by speed, strength, and fatigability)
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Wells/VPHY3100 Lecture Outline Types of muscle cells How skeletal muscle looks How skeletal muscle works The motor unit The neuromuscular junction Excitation/contraction coupling Sarcomere structure & the sliding filament model of contraction Whole-muscle contraction Types of motor units Neural control of skeletal muscle
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The Neuromuscular Junction NMJ
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