제 11 강근육생리 The Skeletal muscle fiber ( 골격근섬유 ) Structure of Muscle Muscle( 근육 )- Muscle fascicles( 근다발 )- Muscle fiber( 근섬유 )- Myofibril( 근원섬유 )- Myofilaments( 근세사 ) - actin, myosin Epimysium( 근바깥막 ) - entire muscle Perimysium( 근다발막 ) - fascicle and fascicle Endomysium( 근섬유막 ) - fiber and fiber 그림 1 골격근섬유의구조
Sarcomere( 근절 ) Z disc M band A band (anisotrophic) I band (isotrophic) H band (hell: bright, hensen) 그림 2 sarcomere
Neuromuscular transmission ( 신경 - 근전달 ) Neuromuscular junction (motor end plate) 운동종판의구조 그림 3 Neuromuscular junction motor neuron : Ach. vesicle 크기약 40nm 한소포체에 10,000-50,000 분자의전달물질시냅스틈새 : 약 20nm muscle membrane(=sarcolemma) 근초 : 근섬유세포막 -흥분성과전도성을가짐. transverse tubule(t-tubule) t 소관 SR( 근장세망 ) 내부 : 10-3 M Ca ++ 외부 : 10-7 M Ca ++ actin myosin
voltaged gated calcium channel voltaged gated sodium channel voltaged gated potassium channel acetylcholine receptor 시냅스전달활동전위전달 Ca channel 활성화 Ca 유리 시냅스소포에작용전달물질반출 (exocytosis) ach는 ach 수용기에결합 sodium channel, potassium channel 활성화 후전위발생 역치이상이면활동전위발생 T 관을타고신호전달 SR 의 Ca channel 활성화 Ca ++ 유리 아세틸콜린의분비 그림 4 아세틸콜린의분비
그림 5 end plate potential end plate potential (EPP, 종판전압 ) minuate end plate potential(mepp, 미세종판전압 ) Molecular characteristics of the contractile filaments ( 수축필라민트의분자적특징 ) myosin filament myosin forms thick filament( 굵은필라민트구성 )
myosin contains ATPase(ATPase 함유 ) myosin binds to the polymerized form of actin ( 액틴과결합 ) actin filament 그림 7 actin filament
tropomyosin strands ( 트로포마이오신 ) : 액틴활성부위를싸고있음 troponin( 트로포닌 ) TNT TNC TNI Interactin of actin and myosin filament( 액틴과마이오신의결합 ) Calcium ions : 칼슘이온은트로포닌과트로포마이오신결합체의기능을억제한다. 그림 8 액틴과구조물 수축에너지원 actin과 myosin의결합보다 myosin과 ATP와의결합이훨씬잘된다. ( 고개떼기 ) ATP ADP + Pi + Energy ( 고개세우기 ) ADP + Pi + 유리에너지 ( 고개구부리기 )
그림 9 근수축에너지원 Steps in contraction and relaxation Contraction Discharge of motor neuron Release of transmitter(acetylcholine) at motor end-plate. Binding of acetylcholine to acetylcholine receptors. Increased permeability of end-plate membrane to Na + and K + Generation of end-plate potential. Generation of action potentialin muscle fiber. Inward spread of depolarization along T tubules. Release of Ca ++ from lateral sacs of sarcoplasmic reticulum and diffusion to thick and thin filaments.
Binding of Ca ++ to troponin C, uncovering myosin binding sites on actin. Formation of cross-linkages between actin and myosin and sliding of thin on thick filaments, procucing shorting. relaxation Ca ++ pumped back into sarcoplasmic reticulum. Release of Ca ++ from troponin. Cessation of interaction between actin and myosin. Relationship between muscle length and tension( 근육의길이와장력간의관계 ) a sarcomere length of 2.0-2.2 microns effectively developed tension 그림 10 근절의길이와장력과의관계
excitation-contraction coupling ( 흥분 - 수축전달 ) 그림 11 흥분 - 수축전달 Mechanics of skeletal muscle contraction ( 근육수축의역학 ) Motor unit : 하나의운동신경과이신경이지배하는골격근섬유의집단 Summation of muscle contraction ( 근육수축의중합 ) Spatial summation ( 공간적중합 ) - 동시에수축하는 motor unit의증가 Temporal summation ( 시간적중합 ) - motor unit의수축빈도의증가
Character of Muscle Contraction Twitch : One action potential occurs muscle contraction with relaxation Tetanus : Repeated stimulus occurs strong contraction Contracted muscle contract again