Muscles

Muscles - constitute 40-50% of the total body weight - produce movement/motion from alternate contraction (shortening) and relaxation Myology – scientific studies of muscles Functions of Muscles: 1. produce movement 2. stabilize body position 3. regulate organ volume 4. generate heat 5. movement of substances in the body Types of Muscle Tissue 1. Skeletal muscle - attached primarily to the bone - moves parts of the skeleton - striated, voluntary 2. Cardiac muscle - form most of the heart - striated, involuntary muscle - has a pacemaker system that causes the heart to beat (autorhythmicity) 3. Smooth muscle - located in the walls of hollow internal organs (stomach, bv, intestine, etc.) - nonstriated/smooth, involuntary Characteristics of Muscle Tissue 1. Excitability/Irritability 2. Conductivity 3. contractility 4. Extensibility 5. Elasticity

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Connective Tissue components: 1. Fascia – sheet or broad band of fibrous connective tissue deep to the skin or around muscles and other organs of the body a. Superficial fascia – immediately beneath the skin - stores water and fat - reduces the rate of heat loss - provides mechanical protection against traumatic blows - provides framework for nerves and blood vessels to enter and exit muscles b. Deep fascia – dense, irregular connective tissue that lines the body walls and limbs and hold the muscle groups together (functional grp) Muscular Organization Skeletal muscle – group of Fascicles – group of muscle fibers – group of myofibrils – group of myofilaments Covering of the muscle tissues 1. Epimysium – whole muscle 2. Perimysium – muscle bundles/fascicles 3. Endomysium – individual muscle fibers • Tendon – cord of dense connective tissue (3 coverings) that attaches a muscle to the periosteum of a bone • Aponeurosis – broad, flat layer of connective tissue attaches a muscle to the coverings of a bone, another muscle or skin

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Nerve Supply *Motor Neuron – these are neurons that stimulate muscle to contract *Motor unit – motor neuron + all muscle fibers it innervates *NMJ – synapse formed between a motor neuron and skeletal muscle fiber - aka Myoneuronal junction *Synapse – a specialized region of connection between neurons *Ach – neurotransmitter in the NMJ - upon release of enough Ach in the NMJ causes a change I the membrane potential of the sarcolema making it permeable to the sodium ion producing muscle action potential leading to muscle contraction Microscopic Anatomy of Skeletal Muscles • Sarcomere – basic functional unit of striated muscle • Sarcolemma – plasma membrane of a muscle cell • Sarcoplasm – muscle cytoplasm • Sarcoplasmic reticulum – fluid filled system, store Ca+ • T Tubules (Transverse) tunnel like in folding of the sarcolemma • Myofibrils – contractile elements of skeletal muscle 3 Types of Myofilaments 1. Thin filament – Actin - composed of * Actin - G actin – basic building block of actin - F actin – polymerized/long fibrous stand of G actin * Tropomyosin - Two strands of tropomyosin are twisted around the double call of F’actin * Troponin - Globular protein, binds to a specific region of the tropomyosin filaments - Has enormous avidity for Ca lons

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2. Thick Filament – Myosin - has two fragments * Light Meromyosin - Responsible for self aggregation properties of Myosin * Heavy Meromyosin - Shaped like the lower ¼ of a hockey stick - Exhibits enzyme like qualities capable of splitting ATP into ADP and PO4 and energy 3. Elastic Filament – Connection Parts of the Sacromere 1. Z disc / line – separates one sacromere from another 2. A Band – dark band, consist mostly of thick filaments and includes portion of thin filaments 3. I Band – light band, consist of thin filaments 4. H Zone – center of each A band containing thick bands 5. M Line – divides the H Zone Sliding Filament Mechanism HOW DO MUSCLE MECHANISM 1. In the relaxed state the regulatory proteins forming part of the actin

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myofilaments event myosin binding Upon action poterial along the sacrolemma, Calcium lons are released from the sacroplasmic reticulum The calcium lons bind with the regulatory proteins, which changes its shape and thereby exposing the myosin binding sites Myosin heads pivot to the center of the sacromere upon attachment to the actin The myosin heads pivot to the center of the sacromere upon attachment to the actin ATP provides the energy needed to release and reposition the myosin heads ready to take another step. (Produce movement like that of the centipede) When the action potential ends the calcium lons are reabsorbed back in the sacroplasmic reticulum, the proteins return back to its original 4

shape and place covering the myosin binding site thereby returning the muscle length back to its original length. Note: only the actin filaments during contraction and slides over the myosin. Muscle Twitch - briet contraction of all the muscle fibers in a motor unit of a muscle - latent period, contraction period, relaxation period - follows the “All or None Principle” Wave/Temporal Summation - stimuli arrive at different times and cause larger contractions Tetanus – sustained muscular stimulation Treppe - staircase effect - muscle is stimulated for some time and is then stimulated to contract by several identical stimuli that are toofar apart for wave summation Recruitment - process of increasing the number of active motor units Types of Ms Contraction 1. Isotonic a. Eccentric b. Concentric 2. Isometric 3. Isokinetic 3 Energy System of Muscle Contraction 1. Phosphagen - utilized phosphocreatine to produce ATP - Maximum contraction lasts for 15 secs

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2. Glycogen-Lactic Acid System - utilizes glucose to produce ATP - Anaerobic process - Maximum contraction lasts for 30 – 40 secs 3. Aerobic System - utilizes oxygen (Biological Oxidation) - this is utilized for activities lasting longer than ½ min 2 Sources of Muscle Oxygen 1. Blood through diffusion 2. Myoglobin * Endurance VS Strength Training Types of Skeletal Ms Fibers According to myoglobin content a. Read Ms fivers – increased myoglobin mitochondria, blood capillaries b. White Ms fibers – low myoglobin According to Metabolic Process 1. Slow Oxidation (Type I) – slow twitch, fatigue resistant 2. Fast Oxidation (Type IIA) – fast twitch A, fatigue resistant 3. Fast Glycolytic (Type IIB) – fast twitch B, fatigable fibers Macroscopic Anatomy 1. Origin – attachment of a muscle tendon to a stationary bone 2. Insertion – attachment of a muscle tendon to a movable bone 3. Belly – fleshy portion of the muscle Note: The muscle groups in the UE and LE are placed in specific compartments so as to determine easily their group muscle action. Upper Extremity Muscle Head and Neck Muscle Facial Muscle

Trunk Muscle LE Muscle

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