各论全册配套完整课件.ppt

1、 Skeletal Muscle Types of muscle: Skeletal muscle骨骼肌 Cardiac muscle 心肌 Smooth muscle平滑肌 Striated muscle 横纹肌 Muscle Muscle contraction The sliding filament mechanism（肌丝滑行机制）（肌丝滑行机制）, in which myosin（肌凝蛋白）（肌凝蛋白） filaments bind to and move actin （肌纤（肌纤 蛋白）蛋白）filaments, is the basis for shortening of st

2、imulated skeletal, smooth, and cardiac muscles. In all three types of muscle, myosin and actin interactions are regulated by the availability of calcium ions. Changes in the membrane potential of muscles are linked to internal changes in calcium release and contraction. Neuronal influences on the co

3、ntraction of muscles is affected when neural activity causes changes in the membrane potential of muscles. Smooth muscles operate in a wide variety of involuntary functions such as regulation of blood pressure and movement of materials in the gut. Muscle contraction 内脏内脏 Structure of skeletal muscle

4、 Skeletal muscles are attached to the skeleton by tendons. Skeletal muscles typically contain many, many muscle fibers. 肌腱肌腱 The sarcomere（肌小节）（肌小节） is composed of: thick filaments called myosin, anchored in place by titin fibers, and thin filaments called actin, anchored to Z-lines . Titin 肌联蛋白 Tit

5、in（肌联蛋白）:从细肌丝的z发起，向粗肌丝内延伸并与M线接触，将粗细肌丝连接在一起 A cross section of sarcomere: each myosin can interact with 6 actin filaments each actin can interact with 3 myosin filaments Sarcomere structures in an electron micrograph. Filaments Myosin 肌凝蛋白 Myosin 肌凝蛋白 Myosin filament (thick filament)粗肌丝粗肌丝 Actin 肌纤蛋白

6、 Tropomyosin 原肌凝蛋白 Troponin 肌钙蛋白 Actin filament (thin filament) 细肌丝细肌丝 Sarcotubular system (1) Transverse Tubule横管 (2) Longitudinal Tubule纵管 Sarcoplasmic reticulum肌浆网 肌膜肌膜 Molecular mechanisms of contraction Contraction myosin binds to actin, pulling the Z-lines closer together, and reducing the wid

7、th of the I-bands. filament lengths have not changed Contraction: myosins cross-bridges（横桥）（横桥） bind to actin; the crossbridges then flex to slide actin. Thick filament (myosin) is actually a polymer of myosin molecule which has a flexible cross-bridge that binds ATP and actin. Cross-bridge cycle re

8、quires ATP The myosin-binding site on actin becomes available, so the energized cross-bridge binds. 1. The full hydrolysis and departure of ADP + Pi causes the flexing of the bound cross-bridge. 2. Binding of a new ATP to the cross-bridge uncouples the bridge. 3. Partial hydrolysis of the bound ATP

9、energizes or re-cocks the bridge. 4. 水解水解 The myosin-binding site on actin becomes available, so the energized cross-bridge binds. 1. The full hydrolysis and departure of ADP + Pi causes the flexing of the bound cross-bridge. 2. Binding of a new ATP to the cross-bridge uncouples the bridge. 3. Parti

10、al hydrolysis of the bound ATP energizes or re-cocks the bridge. 4. The myosin-binding site on actin becomes available, so the energized cross-bridge binds. 1. The full hydrolysis and departure of ADP + Pi causes the flexing of the bound cross-bridge. 2. Binding of a new ATP to the cross-bridge unco

11、uples the bridge. 3. Partial hydrolysis of the bound ATP energizes or re-cocks the bridge. 4. Cross-bridge cycle requires ATP In relaxed skeletal muscle, tropomyosin blocks the cross-bridge binding site on actin. Contraction occurs when calcium ions bind to troponin. This complex then pulls tropomyo

12、sin away from the cross-bridge binding site. Roles of troponin, tropomyosin, and calcium in contraction Interaction of myosin and actin Myosin 肌凝蛋白 Actin 肌纤蛋白 Transmission of action potential along T tubules Calcium release caused by T tubule action potential Contraction initiated by calcium ions Ex

13、citation-contraction coupling 兴奋-收缩偶联 The latent period between excitation and development of tension in a skeletal muscle includes the time needed to release Ca+ from sarcoplasmic reticulum, move tropomyosin, and cycle the cross-bridges. Transverse tubules bring action potentials into the interior

14、of the skeletal muscle fibers, so that the wave of depolarization passes close to the sarcoplasmic reticulum, stimulating the release of calcium ions. The extensive meshwork (网状) of sarcoplasmic reticulum assures that when it releases calcium ions they can readily diffuse to all of the troponin site

15、s. 去极化去极化 肌浆网肌浆网 刺激刺激 大范围的大范围的 传播传播 Passage of an action potential along the transverse tubule opens nearby voltage-gated calcium channels, the ryanodine receptor located on the sarcoplasmic reticulum, and calcium ions released into the cytosol bind to troponin. The calcium-troponin complex pulls tr

16、opomyosin off the myosin-binding site of actin, thus allowing the binding of the cross-bridge, followed by its flexing to slide the actin filament. Which of these following proteins contains the binding sites for Ca2+ that initiates contraction? A Myosin B Troponin I C Tropomyosin D Troponin C E Tro

17、ponin T Neuromuscular transmission Excitation-contraction coupling Muscle contraction General process of excitation and contraction in skeletal muscle A single motor unit（运动单位）（运动单位） consists of a motor neuron and all of the muscle fibers it controls. The neuromuscular junction（ 神经肌接头）神经肌接头）is the p

18、oint of synaptic contact between the axon terminal of a motor neuron and the muscle fiber it controls. Action potentials in the motor neuron cause Acetylcholine（乙酰胆碱）（乙酰胆碱） release into the neuromuscular junction. Muscle contraction follows the delivery of acetylcholine to the muscle fiber. 1. The e

19、xocytosis of acetylcholine from the axon terminal occurs when the acetylcholine vesicles merge into the membrane covering the terminal. 2. On the membrane of the muscle fiber, the receptors for acetylcholine respond to its binding by increasing Na+ entry into the fiber, causing a graded depolarizati

20、on. 3. The graded depolarization typically exceeds threshold for the nearby voltage-gate Na+ and K+ channels, so an action potential occurs on the muscle fiber. Nicotinic acetylcholine receptor 烟碱型乙酰胆碱受体烟碱型乙酰胆碱受体 Acetylcholinesterase 乙酰胆碱酯酶乙酰胆碱酯酶 End plate potential (EPP) 终板电位终板电位 Miniature end plat

21、e potential 微终板电位 Small fluctuations (typically 0.5 mV) in the resting potential of postsynaptic cells. They are the same shape as, but much smaller than, the end plate potentials caused by stimulation of the presynaptic cell. Miniature end plate potentials are considered as evidence for the quantal

22、 release of neurotransmitters at chemical synapses, a single miniature end plate potential resulting from the release of the contents of a single synaptic vesicle. A woman comes to your clinic and explains that she is noting gradually worsening fatigue/weakness in her legs when she goes for her walk

23、. She also mentions a droopy right eyelid, and wonders if this is a normal aging process. You examine her and find the following: overall decreased muscle strength, trace reflexes throughout, and weakness of eyelid closure bilaterally. The rest of the exam is unremarkable. What would you administer

24、to treat the likely condition? A Muscarinic blockers B Nicotinic blockers C Acetylcholinesterase blockers D Alpha blockers E Beta blockers A woman comes to your clinic and explains that she is noting gradually worsening fatigue/weakness in her legs when she goes for her walk. She also mentions a dro

25、opy right eyelid, and wonders if this is a normal aging process. You examine her and find the following: overall decreased muscle strength, trace reflexes throughout, and weakness of eyelid closure bilaterally. The rest of the exam is unremarkable. What would you administer to treat the likely condi

26、tion? A Muscarinic blockers B Nicotinic blockers C Acetylcholinesterase blockers D Alpha blockers E Beta blockers Neuromuscular transmission A Is caused by the release of acetylcholine from the muscle side of the junction B Shows a permeability change to Na+ and K+ at the receptor site during the en

27、dplate potential (EPP) C May be facilitated by curare in myasthenia gravis D Is blocked by curare because it competes with the Na+ entry during the muscle action potential E Is solely an electronic function Neuromuscular transmission A Is caused by the release of acetylcholine from the muscle side o

28、f the junction B Shows a permeability change to Na+ and K+ at the receptor site during the endplate potential (EPP) C May be facilitated by curare in myasthenia gravis D Is blocked by curare because it competes with the Na+ entry during the muscle action potential E Is solely an electronic function

29、A miniature end-plate potential is A Not related to changes in ionic permeability B A reduced action potential in the motor end-plate C Produced by spontaneous release of acetylcholine D Responsible for weak muscular contractions E An afterdischarge at the neuromuscular junction A miniature end-plat

30、e potential is A Not related to changes in ionic permeability B A reduced action potential in the motor end-plate C Produced by spontaneous release of acetylcholine D Responsible for weak muscular contractions E An afterdischarge at the neuromuscular junction The action of acetylcholine at the neuro

31、muscular junction is terminated primarily by A Enzymatic breakdown by choline acetylase B Enzymatic breakdown by acetylcholinesterase C Uptake into the muscle D Uptake into the nerve ending E Diffusion into the surrounding extracellular fluid The action of acetylcholine at the neuromuscular junction

32、 is terminated primarily by A Enzymatic breakdown by choline acetylase B Enzymatic breakdown by acetylcholinesterase C Uptake into the muscle D Uptake into the nerve ending E Diffusion into the surrounding extracellular fluid The transmission of an action potential over the muscle fiber membrane cau

33、ses the contraction of the fiber a few milliseconds later. Which of the following terms is used to describe that process? A Ratchet Theory of Muscle Contraction B Excitation Contraction Coupling C Membrane Potential D All-or -Nothing Law The transmission of an action potential over the muscle fiber

34、membrane causes the contraction of the fiber a few milliseconds later. Which of the following terms is used to describe that process? A Ratchet Theory of Muscle Contraction B Excitation Contraction Coupling C Membrane Potential D All-or -Nothing Law Muscle tension 肌张力 the force exerted on an object

35、by a contracting muscle Load 负荷 the force exerted on the muscle by an object (usually its weight) Isometric contraction 等长收缩 a muscle develops tension but does not shorten (or lengthen) (constant length) Isotonic contraction 等张收缩 the muscle shortens while the load on the muscle remains constant (con

36、stant tension) Mechanics of single-fiber contraction The mechanical response of a single muscle fiber to a single action potential is know as a TWITCH Twitch contraction 单收缩单收缩 Tension increases rapidly and dissipates slowly Shortening occurs slowly, only after taking up elastic tension; the relaxin

37、g muscle quickly returns to its resting length. iso = same tonic = tension metric = length All three are isotonic contractions. 1.Latent period潜伏期潜伏期 2.Velocity of shortening 3.Duration of the twitch 4.Distance shortened Load-velocity relation 长度长度-速度关系速度关系 Answer the following question by referring

38、 to the attached chart. Which curve or line represents the total tension of the muscle? A Curve A B Curve B C Curve C D Curve D E Curve E Answer the following question by referring to the attached chart. Which curve or line represents the total tension of the muscle? A Curve A B Curve B C Curve C D

39、Curve D E Curve E Complete dissipation of elastic tension between subsequent stimuli. S3 occurred prior to the complete dissipation of elastic tension from S2. S3 occurred prior to the dissipation of ANY elastic tension from S2. Frequency-tension relation频率频率-张力关系张力关系 T e m p o r a l s u m m a t i o

40、 n. Unfused tetanus非融合性强直收缩非融合性强直收缩: partial dissipation of elastic tension between subsequent stimuli. Fused tetanus融合性强直收缩融合性强直收缩: no time for dissipation of elastic tension between rapidly recurring stimuli. Frequency-tension relation Mechanism for greater tetanic tension Successive action potent

41、ials result in a persistent elevation of cytosolic calcium concentration Long sarcomere: actin and myosin do not overlap much, so little tension can be developed. Length-tension relation Short sarcomere: actin filaments lack room to slide, so little tension can be developed. Optimal-length sarcomere

42、: lots of actin-myosin overlap and plenty of room to slide. Optimal length Skeletal muscles capacity to produce ATP via oxidative phosphorylation is further supplemented by the availability of molecular oxygen bound to intracellular myoglobin. In skeletal muscle, ATP production via substrate phospho

43、rylation is supplemented by the availability of creatine phosphate磷酸肌酸磷酸肌酸. In skeletal muscle, repetitive stimulation leads to fatigue疲劳疲劳, evident as reduced tension. Rest overcomes fatigue, but fatigue will reoccur sooner if inadequate recovery time passes. On the basis of maximal velocities of s

44、hortening Fast fibers快肌纤维 containing myosin with high ATPase activity (type II fibers) Slow fibers慢肌纤维 - containing myosin with low ATPase activity (type I fibers) On the basis of major pathway to form ATP Oxidative fibers氧化型肌纤维 containing numerous mitochondria and having a high capacity for oxidati

45、ve phosphorylation, also containing large amounts of myoglobin (red muscle fibers) Glycolytic fibers糖酵解型肌纤维 - containing few mitochondria but possessing a high concentration of glycolytic enzymes and a large store of glycogen, and containing little myoglobin (white muscle fibers) Types of skeletal m

46、uscle fibers Slow-oxidative fibers combine low myosin- ATPase activity with high oxidative capacity Fast-oxidative fibers - combine high myosin- ATPase activity with high oxidative capacity and intermediate glycolytic capacity Fast-glycolytic fibers - combine high myosin-ATPase activity with high gl

47、ycolytic capacity Types of skeletal muscle fibers Slow-oxidative skeletal muscle responds well to repetitive stimulation without becoming fatigued; muscles of body posture are examples. Fast-oxidative skeletal muscle responds quickly and to repetitive stimulation without becoming fatigued; muscles u

48、sed in walking are examples. Fast-glycolytic skeletal muscle is used for quick bursts of strong activation, such as muscles used to jump or to run a short sprint. Most skeletal muscles include all three types. Note: Because fast-glycolytic fibers have significant glycolytic capacity, they are sometimes