Locomotor/Musculoskeletal system (Hệ vận động- Sinh lý xương) In this chapter, students will learn: •Components of the musculoskeletal system •Basic of how musculoskeletal system generates motion •Structure of skeletal muscle: muscle fiber, myofibrils, actin and myosin filaments • Structures of a sarcomere •The movements of actin and myosin filaments during muscle contraction •Molecular mechanism of muscle contraction The crossbridge cycle Role of Ca2+ and ATP in muscle contraction •Motor unit •muscle twitch and phases of a muscle twitch •Isotonic and isometric contraction •muscle fatigue •ATP production in muscle cells – Oxygen debt •Structure of bone tissue, bone cells and their function •Osteoblast, osteocyte, osteoclast and their function • long bone elongation and bone remodeling • Structure of smooth muscle and molecular mechanism of smooth muscle contraction Specific terms and keywords • Muscle – Muscular system – Musculature – Neuromuscular junction – Muscle force/tension – Crossbridge – Sarcomere – thin and thick filaments • Skeleton – Skeletal system – Musculoskeletal system – Osteoblast – Osteoclast – Bone modeling/remodeling – Mineralization/calcification Musculoskeletal system Cơ nhị đầu (giãn) Cơ tam đầu (co) • • • • • • muscles bones (the skeleton) cartilage tendons, ligaments joints other connective tissue http://www.helicon.co.uk/images/samples/C00100.gif Muscles and skeletal are main components of locomotor system – striated/skeletal muscle exoskeletal – soft-bodied animals – smooth muscle – cardiac muscle endoskeletal, Hydrostatic skeletal/ hydroskeletal: fluid-filled cavity surrounded by muscles The musculoskeletal system generates motion for animals • Muscles are attached to bones • Bones are connected by joints • Muscle contraction allows motion of the bone attached at the joints • Muscles across joints are arranged in antagonistic groups allowing motion in different directions Skeletal muscle – structure and physiology Structure of a skelelal muscle xương gân Bắp Mô liên kết Bó Sợi Tơ Màng sợi Các sợi bó • Các sợi protein Nhân Muscle body – fascicle • muscle fibers – muscle cell surrounded by sarcolemma: multiple nuclei Cơ tương (chứa myoglobin), myofibrils, protein filaments C.L Standfield.2011 Principles of Human Physiology, 4th edition Structure of a muscle cell Khớp nối thần kinh Túi synap Axon TB thần kinh vận động Khe synap Sợi Tận vận động ống T nhân Màng bao Lưới tương Lưới tương ống T Tơ Ti thể Sợi dày (myosin) Fig 12.2 C.L Standfield.2011 Principles of Human Physiology, th edition Sợi mỏng (actin) Myofibril and sarcomere Đĩa A Vạch Z Đĩa I Vạch M Sợi dày • Sợi mỏng • • • Fig 12.2 C.L Standfield.2011 Principles of Human Physiology, 4th edition Thick and thin filaments are orderly arranged (in a 1:2 ratio) showing striped appearance (hence the name striated muscle) Z line M line Sarcomere (Đơn vị co cơ): the structure between two neighbouring z lines Structure of a sarcomere Sarcomere A band ( dark band) Z-line I band (light band) myosin H zone actin •A band ( dark band): thick filaments overlapped with thin filaments at the two ends •H zone: center region of A band where only thick filaments are present I band (light band) www.arn.org/docs/glicksman/eyw_040901.htm • I band: structure between A bands where only thin filaments are present Bone functions - supporting the body allowing motion protecting vital organs storage system for calcium and phosphorus forming blood cells Bone shapes • • • • • long bones short bones flat bones irregular bones sesamoid bones Axial skeleton http://en.wikipedia.org/wiki/Axial_skeleton Appendicular skeleton http://en.wikipedia.org/wiki/Appendicular_skeleton Structure of bone tissue • Connective tissue • bone cells • Bone matrix (Khuôn ngoại bào Tế bào xương Tế bào hủy xương Tế bào tạo xương Khuôn ngoại bào khoáng hóa Fig.21.13 C.L Standfield.2011 Principles of Human Physiology, 4th edition khoáng hóa) Bone matrix • Organic part: 35% – Osteoid containing collagen, proteoglycan – Bone Elasticity • Inorganic part: 65% – Hydroxyapatite (a calcium phosphate- Ca10(PO4)6(OH)2) – Bone stiffness and rigidity • Balance between elasticity and rigidity gives bone its strength Bone cells • Osteoblast (Tế bào tạo xương): bone forming cells – “bone maker” • Osteocyte (Tế bào xương): mature bone cells • Osteoclast (Tế bào hủy xương): bone resorbing cell –”bone breaker” Osteoblasts and ossification • Osteoblasts – Lay down/ produce bone matrix: osteoid (collagen, proteoglycan) • vesicles containing Ca2+, PO4 2-, enzymes -> hydroxyapatit – Osteoid is then calcified (calcification/ mineralization) http://www.sciencephoto.com/media/435812/view • Ossification (osteogenesis) is the process in which osteoblasts lay down new bone tissue Osteocytes • Osteoblasts produce bone matrix and get “trapped”/immobilized in the matrix - > osteocytes trapped in lacunae • osteocytes maintain the bone matrix and no longer produce new bone tissue http://faculty.une.edu/com/abell/histo/histolab3.htm • Osteocytes contact/connect to each other and to nearby osteoblasts by long processes (canaliculi): exchange materials(oxygen, nutrients, wastes…) taken by cells close to blood vessels http://www.denniskunkel.com/index.php?module=media&pId=102&id=10665 Osteoclasts • Giant cells, multinucleated, ruffled border • Bone resorptive activity: – acids (HCl) dissolve inorganic compounds (hydroxyapatite) of bone http://faculty.une.edu/com/abell/histo/osteoclast.jpg matrix > release Ca, P – Enzymes break down osteoid (collagens, proteins in bone matrix) http://www.biology-online.org/js/tiny_mce/plugins/imagemanager/files/boa002/AN-nothingF03.jpg Bone is a dynamic tissue • Bone tissue can: – grow during childhood – heal following a fracture – changes its structure in response to forces applying on it – renew its structure • Bone modeling and bone remodeling Long bone elongation • Under the influence of GH: – Epiphyseal plate (EP)containing cartilage – Chrondrocytes in the EP increase in size and numberforming thicker cartilage layer -> wider EP – Cartilage adjacent to the shaft is replaced by bone-> new bone added to the bone shaft -> elongated bone length – When EP is completely filled by bone (late adolescence)-> epiphysial plate closure Sụn tiếp hợp đầu xương Đầu xương Fig 21.15 C.L Standfield.2011 Principles of Human Physiology, 4th edition • sex hormone (androgens and estrogens) -> plate closure • When plate closure occurs -> no more bone elongation -> no more increases in height (normally after adolescence ) Bone remodeling (Qúa trình tái tạo xương) www.cptc.ctc.edu/library/Bio%20118%20Lecture% Factors affect bone growth and development • Vitamin D: Ca2+ absorption – Sunlight exposure – fat absorption (vitamin D is fat-soluble) – Rickets and vitamin D deficiency • Vitamin C: collagen • Hormones: GH, Thyroid hormones, sex hormones: estrogen, testosterone Structure of smooth muscle, compared with skeletal muscle C.L Standfield.2011 Principles of Human Physiology, 4th edition Smooth muscle • spindle-shaped, uninucleated with a centrally located nucleus • Thick and thin filaments are obliquely arranged in various directions • No sarcomere structure -> not striated (no striation) • Dense body (Thể hạt) transmit contractile force to the cell’s exterior Contraction occurs along several axes • C.L Standfield.2011 Principles of Human Physiology, 4th edition Molecular mechanism of smooth muscle contraction •G-protein coupled Receptor • extracellular Ca 2+ •Camodulin •Myosin kinase C.L Standfield.2011 Principles of Human Physiology, 4th edition [...]... forming actin strands found in thin filaments 2 regulatory proteins control the contraction of muslce fiber • Tropomyosin: long fibrous molecule extending over actin monomers to block the myosin-binding site when muslce is at rest • Troponin complex consists of 3 subunites: – One attaches to the actin strand – One binds tropomyosin – One is the site for reversible binding with Ca2+ Fig 12.5 C.L Standfield.2011... tubules): membranous tubules formed by deep invagination of sarcolemma into the cytoplasm of the muscle cell T- tubules transmit action potential High Ca2+ concentration in lumen of the SR (sarcoplasmic reticulum) when muscle relaxed Molecular mechanism of muscle contraction, step 1: acetylcholine release and the generation of action potential in the motor end plate of neuromuscular junction • Neuromuscular... and all the muscle fibers innervated by that neuron are collectively defined as a motor unit http://academic.wsc.edu/faculty/jatodd1/351/motor_unit.jpg Isometric and isotonic contraction • isometric contraction (Co cơ đẳng trường): - Tension created, but muscle does not shorten as the load is greater than the force generated – Unchanged muscle length Co cơ đẳng trường • isotonic contraction (Co cơ đẳng... the length of muscle fiber (created by length of the sarcomeres, not by the number of sarcomeres in series) at the onset of contraction • Muscle at optimum length generates greatest force Increase in the number of active motor units increases force for whole muscles: recruitment C.L Standfield.2011 Principles of Human Physiology, 4th edition The size principle Muscle fatigue • Muscles differs in their... frequency of muscle stimulation where independent twitches follow one another closely such that the peak tension rises in stepwise fashion with each twitch until eventually it reaches a constant level Factor affecting the force generated by individual muscle fibers: Frequency: high stimulus frequency causes summation and tetanus • High Ca2+ level in the cytosol Factors affecting the force generated by individual... whole muscle to a single action potential – Lag/latent peroid (Giai đoạn tiềm tàng ): 2ms: delay time between the action potential in the muscle cell and the start of contraction ( release of Ca 2+ ) – contraction phase (Giai đoạn cơ co) : 10100 ms: time between the end of latent period and the peak of muscular tension: increasing cytosolic Ca2+ levels, increasing active actin-myosin crossbridges – relaxation... moderate exercise • Glucose 6O2 + 38 ADP + 38 P -> 6CO2 + 6H2O+ 38 ATP • Effective; glucose, fatty acids and amino acids can be used • slow – anaerobic respiration: heavy exercise • Glucose -> pyruvate -> 2 ATP + 2 acid pyruvic lactate • less effective (2ATP) • Fast • Oxygen debt: The additional oxygen that must be taken into the body after vigorous exercise to restore all systems to their normal states... Regarding muscle contraction process, What would happen if: 1 Na+ ion channels were blocked and there was no movement of Na+ through membrane of muscle cells ? 2 There was an insufficient amount of ATP available in the muscle cells ? 3 There were an sufficient amount of ATP and an excess amount of Ca2+ available in the cytosol of muscle fibers ? Muscle twitch and its phases • A twitch is the mechanical... available in the cytosol Neurotoxins and muscle paralysis • Spastic paralysis stiffness of the muscles and muscular spasms (Liệt co cứng ): + insecticides, chemical weapons inhibit AChE • Flaccid paralysis (Liệt mềm nhũn ): a weakness or lack of muscle tone + Snake venom + Curare + Botulinum (Clostridium botulinum)- botulism http://mynotes4usmle.tumblr.com/post/34773331063/houseofmind-theneuromuscular-junction-nmj... decreases the oxidative capacity and increase glycolytic capacity of muscle fibers (reduces muscle resistance to fatigue)-> converting a portion of fast oxidative fibers into fast glycolytic fibers: – decreases in size and number of mitochondria – Increases in the concentration of glycolytic enzymes – Increases in fiber diameter (new myofibrils are synthesized) • Muscle hypertrophy • Muscle atrophy (teo