Muscular System Lecture Outline PDF

Lecture Outline The Muscular System 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. After this lecture,...

Lecture Outline The Muscular System 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. After this lecture, students should be able to 1. name, differentiate the morphology and function of different types of muscle 2. describe the microscopic structures of different types of muscle 3. state the energy sources for muscle contraction 4. describe the mechanisms of muscle contraction 5. understand the muscular disorders 2  Functions and Types of Muscles 1. Smooth Muscle 平滑肌  Locates in the walls of hollow internal organs and blood vessels （e.g. stomach, small intestine and blood vessels）  Contractions involuntarily不隨意的  Moves materials through organs and regulates blood flow  Has cylindrical cells with pointed ends  Each cell is uninucleated 單核的 Picture Source: Mcgrawhill company. Picture Source: Mcgrawhill company. 3  Picture Source: Mcgraw hill company. 2.Cardiac Muscle 心肌  Forms the heart wall  Has uni-nucleated, striated紋狀的, tubular and branched fibers  permits contractions to spread quickly across the heart, through intercalated disks 閏板 that joins the fibers  does not require outside nervous stimulation to contract  Affected by nerves that regulate heart rate and strength of contraction 4 Picture Source: Mcgraw hill company. 3. Skeletal Muscle 骨骼肌  Fibers are tubular, multinucleated and striated  Are those muscles attach to the skeleton  Contraction is voluntary 隨意的 Picture Source: Mcgrawhill company. 5  Physiology of skeletal muscles  Functions  Support the body  Make bones and other body parts move  Help maintain a constant body temperature  Assists fluid movement in cardiovascular and lymphatic vessels  Protect bones, internal organs, and stabilize joints 6 Skeletal muscles: Anatomy Connective Tissue Coverings of Skeletal Muscle  Endomysium 肌內膜 Thin layer of areolar connective tissue網狀結締組織 Surrounds each skeletal muscle fiber (cell) Perimysium 肌束膜 – Source: people.eku.edu  Surrounds bundles of muscle fibers (fascicles 束)  Epimysium 肌外膜 Layer that surrounds the entire muscle Becomes part of the fascia 筋膜 (separates muscles from each other) Collagen fibers extend from epimysium to form tendons that attach muscles to bone 7 Connective tissue of a skeletal muscle Cross section of the arm showing the arrangement of the muscles, which are separated from the skin by fascia. The superficial fascia contains adipose tissue Trace the connective tissue of a muscle from the endomysium to the perimysium to the epimysium, which becomes a part of the deep fascia and from which the tendon extends to Photomicrograph of muscle fascicles from the tongue attach a muscle to the periosteum of a bone where the fascicles run in different directions 8 (c.s.=cross section; l.s.=longitudinal section Microscopic Anatomy of a Muscle 9 Microscopic Anatomy of skeletal muscle 2. Muscle fiber components  Sarcolemma 肌纖維膜 – plasma membrane  Sarcoplasm 肌質– cytoplasm  Contains glycogen that provides energy for muscle contraction  Contains myoglobin which binds oxygen until needed  Sarcoplasmic reticulum 肌質網 – endoplasmic reticulum  T- (transverse) tubules  Formed by the sarcolemma penetrating into the cell  Come into contact with expanded portions of the sarcoplasmic reticulum Structure of muscle: 10 https://www.youtube.com/watch?v=SCznFaTwTPE Picture Source: Mcgrawhill company. 3. Myofibrils 肌原纖維 and Sarcomeres  Myofibrils run the length of the muscle fiber  Composed of numerous sarcomeres  Extends between two vertical Z lines  Contains two types of protein myofilaments - Thick filaments are made up of - myosin 肌球蛋白 - Thin filaments are made up of - actin 肌動蛋白, - tropomyosin 原肌球蛋白, health-pictures.com - troponin 肌鈣蛋白  I band contains only thin filaments  A band in the center of the sarcomere contains thick and thin filaments  M band is a fine dark band in the center of the H zone  H zone in the center of the A band has only myosin 11 filaments 12 4. Myofilaments  Thick filaments  Composed of several hundred of molecules of myosin  Myosin molecules end in a cross-bridge  Thin filaments  Two strands of actin  Double strands of tropomyosin coil of each actin strand  Troponin occurs at intervals on the tropomyosin strand THIN 1 Cross-bridge 2 THICK Picture Source: Mcgrawhill company. 13  Physiology of skeletal muscle 1. Sliding filaments  Occurs when sarcomeres shorten (during muscle contraction)  Actin filaments slide past the myosin filaments  Thick and thin filaments remain the same length 14  Sliding filaments  Occurs when sarcomeres shorten (during muscle contraction)  Actin (thin) filaments slide past the myosin (thick) filaments  Thick and thin filaments remain the same length Sliding Filament Theory Of Muscle Contraction Explained https://www.youtube.com/watch?v=nTZnBdeIb5c 15  Nerve Synaptic vesicles with ACh Axon terminal Neuromuscular Junction, Animation https://www.youtube.com/watch?v=zbo0i1r1pXA https://www.youtube.com/watch?v=ZscXOvDgCmQ sarcolemma muscle 2. Neuromuscular junction (NMJ)  Axon terminals 軸突終端 Synaptic cleft  Come into close proximity to the sarcolemma  Have vesicles that contain acetylcholine 乙醯膽鹼(ACh)  Synaptic cleft 隙 – a small gap that separates the axon from the sarcolemma 16 Neuromuscular junction acetylcholine 17 Skeletal muscle contraction Steps https://www.youtube.com/watch?v=sZuy356qkPM 1. Nerve signal (action potential) arrives at the axon terminal. 2. The synaptic vesicles release a neurotransmitter named Acetylcholine (ACh). ACh binds to receptors on the motor end plate (membrane). 3. The binding of ACh to the receptors increases the membrane permeability to Na+. Na+ rushes into the cell. 4. An action potential occurs across the surface of sarcolemma and also travels T tubules down the T tubules triggers release of Ca2+ in the terminal cisternae 槽 which is an enlarged portion of sacroplasmic reticulum. 5. Ca2+ causes the filaments to slide past one another. ACh is broken down by AChE (Acetylcholinesterase, 18 cholinesterase). The Role of Actin and Myosin Actin molecules a. When Ca2+ intracellular level is low (muscle is relaxed), myosin binding sites on actin molecules are covered by tropomyosin. b. When released calcium from sacroplasmic reticulum combines with troponin, myosin binding sites are exposed. Each myosin head has two binding sites 1. Actin binding site 2. ATP binding site 19 In relaxed muscle, tropomyosin covers myosin binding sites on actins. When calcium binds to troponin, myosin binding site is exposed. After breaking down ATP, myosin heads bind to actin filaments, forming cross-bridges. Then, release of ADP and Pi creates a power-stroke that causes actin to move. Myosin head detaches and returns to resting after binding another ATP. 20 Muscle Contraction - Cross Bridge Cycle, Animation. - YouTube Energy for Muscle Contraction  ATP present before strenuous 費力的 exercise only lasts a few seconds  Muscles acquire new ATP in three ways 1. Creatine phosphate 肌磷酸 breakdown 2. Cellular respiration 細胞呼吸作用 3. Fermentation 發酵作用 21 丙酮酸鹽 22 1. Creatine Phosphate(肌磷 酸)Breakdown  Does not require oxygen (anaerobic厭氧的)  Regenerates ATP by transferring its phosphate to ADP  Fastest way to make ATP available to muscles  ATP produced only lasts about 8 seconds 23 2. Cellular Respiration  Usually provides most of a muscle’s ATP  Uses glucose from stored glycogen and fatty acids from stored fats  Required oxygen  Myoglobin can make oxygen available to muscle mitochondria  Carbon dioxide and water are end products Heat is a by-product 24  3. Fermentation  Anaerobic process  Produces ATP for short bursts of exercise  Glucose is broken down to lactate (lactic acid) 25  Oxygen Debt 氧債  the extra oxygen, taken in by the body during recovery from exercise, beyond the resting needs of the body. Occurs when muscles use fermentation to supply ATP Requires replenishing 補充 creatine phosphate supplies and disposing of 去除 lactic acid 乳酸 26  Smooth Muscle: Structure Smooth muscle fibers contain thick and thin filaments  Filaments are not arranged into myofibrils that create striations  Thin filaments are anchored directly to the sarcolemma called dense bodies 27 Smooth Muscle: Contraction When contracted, the elongated cells become shorter and wider Contraction occurs very slowly Contractions can last for long periods of time without fatigue 28 Functional organization of skeletal muscle The Motor Unit and Recruitment in Skeletal Muscle - YouTube o Motor unit A nerve fiber together with all of the muscle fibers that the nerve innervates 受神經支配 The number of muscle fibers within a motor unit can differ (1: 23 in ocular 眼的 muscle; 1:1000 in Gastrocnemius 腓腸肌) Obeys the all-or-none law o Recruitment As the intensity of nervous stimulation increases, more motor units are activated (tetanic contraction) Results in stronger muscle contractions o Muscle Tone Generated by parts of muscle fibers contracting Important in maintaining posture 29 Motor Unit Single motor neuron All muscle fibers controlled by motor neuron The number of muscle fibers within a motor unit can be different Motor neuron: muscle fiber 1: 23 (ocular 眼的 muscle) 1:1000 (gastrocnemius 腓腸肌) 30 Skeletal Muscle adaptation Athletics and muscle contraction  Size of muscles  Atrophy 萎縮 – a decrease in muscle size  Hypertrophy 過度生長 – an increase in muscle size https://thesushantkumar.com/2019/09/16/understanding-hypertrophy-repetition-range-to-build-muscle/ 31  Skeletal muscle: fiber types 1. Slow-twitch fibers (Type I fibers) 2. Intermediate-twitch fibers  Tend to be aerobic (Type IIa fibers)  Have more endurance  All the same features as  Have many mitochondria slow-twitch fibers, but much faster  Dark in color because they contain myoglobin 肌紅蛋白  Called fast aerobic fibers  Highly resistant to fatigue  Used in moderate activity 32 3. Fast-twitch fibers (Type IIb fibers)  Tend to be anaerobic  Designed for strength  Light in color, fewer mitochondria, little or no myoglobin, and fewer blood vessels than slow-twitch fibers  Vulnerable to accumulation of lactic acid and can fatigue easily 33  Skeletal Muscles of the Body Basic terms  Origin – attachment of a muscle to the immovable bone  Insertion – attachment of a muscle to the bone that moves  Prime mover (Agonist) – muscle that Picture source: The McGrawhill company Inc。 does most of the work in a movement  Synergist – muscles that assist the prime mover  Antagonists – muscles that work opposite one another to bring about movement in opposite directions E.g. biceps as prime mover contract while triceps relaxed as antagonist 34  Skeletal Muscles of the Body Naming Muscles  Size e.g. gluteus maximus 臀大肌  Shape e.g. deltoid 三角肌  Direction of fibers e.g. rectus abdominis 腹直肌  Location e.g. pectoralis 胸肌  Attachment e.g. brachioradialis 肱橈肌  Number of attachments e.g. biceps brachii  Action e.g. extensor digitorum 指伸肌/趾伸肌 Picture source: The McGrawhill company Inc。 35 36 Muscles of the Head and Neck 額肌 口輪匝肌 胸鎖乳突的 斜方肌 37 Muscles of the Head and Neck 38 Muscles of the Trunk Muscles of the thoracic wall  External intercostal muscles 肋間肌  Diaphragm 胸大肌  Internal intercostal muscles Muscles of the 腹直肌 腹橫肌 abdominal wall 內斜肌 外斜肌  External and internal obliques  Transversus abdominis Rectus abdominis 39   Muscles of the Trunk Lateral rotation of trunk Waist flexion Reference: ExRx.net. (2010). Exercise & Muscle Directory. Retrieved from 40 http://www.exrx.net/Lists/Directory.html. Muscles of the Shoulder Muscles that move the scapula  Trapezius  Serratus anterior 前鋸肌 Muscles that move the arm  Deltoid  Pectoralis major  Latissimus dorsi 背闊肌  Rotator cuff muscles  Supraspinatus 棘上肌  Infraspinatus 棘下肌  Teres minor 小圓肌  Subscapularis 肩胛下肌 41 Muscles of the Shoulder and Upper Limb 42  Muscles of the Arm and Forearm Muscles of the Arm  Biceps brachii  Brachialis  Triceps brachii Muscles of the Forearm  Flexor carpi and extensor carpi  Flexor digitorum and extensor digitorum Copyright to McGraw-hill publisher 43 Muscles of the Shoulder and Upper Limb 44 Muscles of the Hip and Lower Limb Muscles that move the thigh  Iliopsoas 髂腰肌  Gluteus maximus 臀大肌  Gluteus medius 臀中肌  Adductor group muscles  Pectineus 恥骨肌  Adductor longus 長收肌  Adductor magnus 大收肌  Gracilis 股薄肌 45 Muscles of the Hip and Lower Limb 46 Muscles of the Hip and Lower Limb Muscles that move the leg  Quadriceps femoris group 股四頭肌  Rectus femoris 股直肌  Vastus lateralis 股外側肌  Vastus medialis 股內側肌  Vastus intermedius 股中間肌  Sartorius 縫匠肌  Hamstring 腿窩 group  Biceps femoris 股二頭肌  Semimembranosus 半膜肌  Semitendinosus 半腱肌 47 48 Common neuromuscular disorders Tetanus 破傷風 - a serious, bacterial disease that affects the nervous system  Pathogenesis  Caused by Clostridium tetani, a spore-forming bacillus  The vegetative form is an anaerobe, thriving deep in tissues, for example, in a puncture wound  The exotoxin enters the nervous system, causing tonic muscle spasms  Symptoms of infection  Jaw stiffness, difficulty swallowing, stiff neck, headache, skeletal muscle spasm and eventually respiratory failure 49  Common neuromuscular disorders Muscular dystrophy (Duchenne muscular dystrophy) 肌肉萎縮症 - A metabolic defect, a deficit of dystrophin (a muscle cell membrane protein) leads to degeneration and necrosis of the cell  Pathogenesis  Skeletal muscle fibres are replaced by fat and fibrous connective tissue (leading to the hypertrophic appearance of the muscle), muscle function is gradually lost  Signs and symptoms  Imbalance between agonist and antagonist muscles lead to abnormal postures and the development of contractures and joint immobility 50 Common neuromuscular disorders Myasthenia gravis 重症肌無力 - a neuromuscular disease  Pathogenesis  IgG autoantibodies to ACh receptors form blocking and ultimately destroying the receptor site  Prevent any further stimulation of the muscle  Leads to skeletal muscles weakness and rapid fatigue of the affected muscles such as facial and ocular muscles initially, followed by the muscles of arm and trunk  Signs and symptoms  Muscle weakness in the face and eyes  Fatigue develops quickly when the muscles are being used 51 Homeostasis Cardiac muscle  Contract forces blood into the arteries and arterioles Smooth muscle  Found in arteries and arterioles help maintain blood pressure  Moves food along the digestive tract and assists in the voiding of urine Skeletal muscles  Protect internal organs and stabilizes joints  Active during breathing  Produce heat to maintain normal body temperature during contraction  Allows us to relocate our bodies 52