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發表於 2018-12-27 16:36
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01 Bones and Skeletal Muscles 骨与骨骼肌; n# z, l$ `( L% r
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#10-12 Skeletal muscle contractions 骨骼肌收缩 A# m. O) a" m6 B- F/ e
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|) j% R) U, Z9 U#10 Skeletal muscle contractions 骨骼肌收缩
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+ ^: _9 y; S& I4 q, EThe muscular, nervous, and skeletal systems interact to produce movement. Messages travel through the nervous system to the skeletal muscles that attach to bones throughout the body. The fibrous appearance of skeletal muscles is created by the arrangement of proteins inside the cells that form muscle tissue.
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9 ]- C+ m( E' ?9 ^5 v肌肉、神经和骨骼系统的相互作用产生运动。信号通过神经系统传递到附着于全身骨骼的骨骼肌。骨骼肌的纤维外观是由形成肌肉组织的细胞内蛋白质排列所致。
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2 W* s6 g' A( x3 h" T& }' E8 nMotor neurons of the nervous system connect with these skeletal muscles. Movement occurs through a series of steps. Impulses from the nervous system reach the neuromuscular junction. The neuron releases a neurotransmitter called acetylcholine. It binds to receptors on the muscle and begins a chemical reaction within its fibers. The muscle filaments slide across each other and the muscle shortens, or contracts. This action produces movement.
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. V1 v7 e: G0 Q% @1 B神经系统的运动神经元与这些骨骼肌连接,运动通过一系列步骤完成。冲动从神经系统传到神经-肌接头,神经元释放一种叫乙酰胆碱的神经递质,与肌肉的受体结合,促发肌纤维内的化学反应。肌丝相对滑动,肌肉缩短或收缩,这个作用形成运动。
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#11 Muscle contraction: Action potential 肌肉收缩:动作电位
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In order to produce movement in the body, the muscular, nervous, and skeletal systems interact in a process called muscle contraction. Muscle contraction begins when the nervous system generates a signal. 0 K! z5 X4 N4 M E1 K3 V
6 i; C" _# `# e y! Z: y为了让机体产生运动,肌肉、神经和骨骼系统通过称为肌肉收缩的过程相互作用。神经系统产生信号时,肌肉收缩即开始。
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) E8 [8 O3 i) x# @A motor neuron conducts an action potential to its link with a muscle fiber. At the neuromuscular junction, a neurotransmitter called acetylcholine is released. This chemical binds to receptors on the muscle fiber. Acetylcholine receptors are chemically-gated ion channels, allowing an influx of sodium ions into the muscle fiber. This stimulates the sarcolemma and generates another action potential that travels through tiny folds know as transverse tubules. The action potential reaches myofibrils within the muscle fiber. Surrounding the myofibrils are membranous sacs called the sarcoplasmic reticulum. The arrival of the action potential triggers the release of calcium ions stored in the sarcoplasmic reticulum. They diffuse into the muscle fiber and the next phase of muscle contraction begins.; c9 C, ?4 L. D- @
' _' K9 D% m; n2 ~; r运动神经元将动作电位传导至与其相连的肌纤维,在神经-肌接头释放一种叫乙酰胆碱的神经递质,这些化学物质与肌纤维受体结合。乙酰胆碱受体为化学门控离子通道,与乙酰胆碱结合使通道开放,让钠离子内流到肌纤维内。这刺激了肌膜,产生另一个动作电位,跨过横小管的细小折叠,动作电位抵达肌纤维内的肌原纤维。包绕肌原纤维的是称为肌质网的膜囊,动作电位抵达后,促发释放肌质网中储存的钙离子,弥散分布到肌肉纤维内,开始肌肉收缩的下一阶段。
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#12 Muscle contraction: Cross bridge formation 肌肉收缩:横桥形成
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When an action potential travels to a muscle fiber, a series of steps begin within the fiber that result in contraction. Muscle fibers are organized into units called sarcomeres that contain two types of filaments. Thick filaments consist of myosin. Thin filaments consist of actin. Eventually these two filaments will come together, creating a cross bridge. In response to an action potential, the sarcoplasmic reticulum within a muscle fiber release calcium ions. These ions bind to protein complex causing it to shift and expose the myosin binding sites. The myosin head then binds to actin and the cross bridge is established./ e! x) P' Z5 A! m$ l6 U3 _* \
8 j3 G4 D9 h9 n当动作电位传到肌纤维,在纤维内会发生一系列步骤而造成收缩。肌纤维以肌节为单位排列,含有两类细丝,粗肌丝含有肌球蛋白,细肌丝含有肌动蛋白,这两种肌丝最终结合在一起,构成横桥。肌纤维内的肌质网对动作电位作出反应,释放钙离子。这些钙离子与肌钙蛋白结合,使其转变并暴露肌球蛋白结合位点,肌球蛋白头部与肌动蛋白结合,建立起横桥。8 g$ c$ m0 P8 ~ Q+ X7 ]
- q6 T+ l4 @1 z+ i p2 XIn the next step, ADP and phosphate are released. Their energy powers the movement of the myosin head. This step is called the power stroke. Actin moves toward the center of the sarcomere. ATP then binds again to myosin and it detaches from actin. ATP breaks down into ADP+Phosphate and the myosin head cocks back. Myosin heads continue to deactivate and reactivate. This causes the myosin filaments to pull together and slide across one another, contracting the muscle.+ M* J3 f, a! e' Z" `! \
- Q+ W0 @! [$ ]) m& W0 G; ?下一步便是释放ADP和磷酸盐,其能量驱动肌球蛋白头部运动,这一步骤称为动力冲程,肌动蛋白朝肌节中心运动。肌球蛋白再与ATP结合,从肌动蛋白分离。ATP降解为ADP与磷酸盐,肌球蛋白头部复位。肌球蛋白头部持续失活并复活,这样让粗肌丝一起牵拉,彼此相互滑行,从而收缩肌肉。
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: J( |6 j: ^9 k$ [0 @载点 https://pan.baidu.com/s/15uy6HRBDKdqyXJNsdExddw A* r% S, |# y. C# d9 v/ R; h, C
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