影響橫紋肌收縮效能的因素

1、影響橫紋肌收縮效能的因素,肌肉的收縮形式:等長(zhǎng)收縮(isometric contraction)： 等張收縮(isotonic contraction)： Resting tension,,Non-contractile and connective tissue in muscle itself,Tendon,張力不變，長(zhǎng)度減小,長(zhǎng)度不變，張力增加,Isometric contraction,isotonic contract

2、ion,Isotonic Isometric,負(fù)荷的形式,(1)、前負(fù)荷（preload）：肌肉收縮前已經(jīng)存在的負(fù)荷，它使肌肉在安靜時(shí)即有初長(zhǎng)度；(2)、后負(fù)荷（afterload）肌肉收縮后方能“感覺(jué)”到的負(fù)荷；,Isometric contraction,isotonic contraction,Preload（長(zhǎng)度-張力曲線）,F1,F3,,Initial length & p

3、reload,F2,Passive tension is the tension developed by simply stretching a muscle to different lengths ( think of a rubber band).Passive tension is determined by preload and the elasticity of the muscle itself.,,The act

4、ive tension is maximal when there is maximal overlap of thick and thin filaments and maximal cross-bridge,2 to 2.2?m in vivo,Preload（長(zhǎng)度-張力曲線）,長(zhǎng)度-張力關(guān)系,前負(fù)荷對(duì)肌收縮的影響,,最適前負(fù)荷（初長(zhǎng)）,,,,,,1.5µm,0.65,0.65,0.35,0.35,0.20,,M,骨骼肌

5、體內(nèi)所處自然長(zhǎng)度 肌小節(jié) 2.0-2.2µm粗、細(xì)肌絲理想重疊/收縮,,,肌小節(jié),,,Z,Z,最適初長(zhǎng)度：使肌肉收縮時(shí)產(chǎn)生最大張力的初長(zhǎng)度。最適前負(fù)荷：產(chǎn)生最適初長(zhǎng)度的前負(fù)荷。 　在最適初長(zhǎng)度和前負(fù)荷時(shí)，肌張力最大，收縮速度最快，縮短的長(zhǎng)度最大，橫橋與細(xì)肌絲結(jié)合最多，作功效率最高。Increasing preload does not affect latent period and sligh

6、tly reduces the distance shortened,,,長(zhǎng)度-張力關(guān)系,在有后負(fù)荷的情況下，肌肉能否縮短、其縮短速度，取決于肌肉收縮產(chǎn)生的張力與負(fù)荷的力量對(duì)比。,c,Experiment,afterload（張力-速度曲線）,Effects of afterload on fiber shortening,afterload（張力-速度曲線）,在有后負(fù)荷的情況下，肌肉能否縮短、其縮短速度，取決于肌肉收縮產(chǎn)生的張力與負(fù)荷

7、的力量對(duì)比,9,Experiment,Increasing afterload increase the latent period and reduces the distance shortened,The force of muscle contraction.,,,Because:,The speed of muscle shortening depends on the speed of cross-bridge cyclin

8、g.The force developed depends on the number of cross-bridge formed.As the afterload on the muscle increases, the velocity will be decreased because cross-bridge can cycle less rapidly against the higher resistance.,肌

9、肉的縮短速度取決于橫橋周期的長(zhǎng)短，收縮張力取決于每一瞬間與肌動(dòng)蛋白結(jié)合的橫橋的數(shù)目。,Afterload & Power,POWER = FORCE x VELOCITY physiological power = strength of muscle contraction x velocity of muscle contractionP=?L?V,Muscle fiber can shorten rap

10、idly or develop high forces but not at the same timePeak power occurs at approximately 1/3 maximum shortening velocity.,,負(fù)荷對(duì)肌肉收縮的影響,負(fù)荷越大，肌肉收縮時(shí)最終產(chǎn)生的張力越大出現(xiàn)縮短的時(shí)間越晚縮短的程度越小縮短的速度越小,正性肌力：Adr、Ca+等負(fù)性肌力：缺氧、酸中毒等,收縮性：影響肌收縮效果的內(nèi)

11、部機(jī)能狀態(tài),Length,Force,肌肉收縮能力,Contractility is determined by the level of intracellularCa2+, the activity of myosin and ATPase, etc. In vivo, the contractility of the muscle is regulated by hormones, drugs, and some other

12、 humoral substances.,The difference of muscle fiber,運(yùn)動(dòng)單位數(shù)量的總和：size principle頻率效應(yīng)的總和。,收縮的總和,收縮的總和,單收縮,復(fù)合收縮,不完全強(qiáng)直收縮,twitch,incomplete tetanus,完全強(qiáng)直收縮(complete tetanus),,4 收縮的總和,收縮特點(diǎn):,體內(nèi)肌收縮多為復(fù)合收縮。復(fù)合收縮幅度高于單收縮。收縮可以發(fā)生復(fù)合，但A

13、P是分離的。單收縮可以是等長(zhǎng)收縮，也可以是等張收縮。骨骼肌收縮的強(qiáng)度與參與的肌纖維數(shù)目和單個(gè)肌纖維的收縮幅度有關(guān)。,,A muscle that when contracted acts to bend a joint or limb in the body.,,summary,1. A mechanism consisting of a pawl that engages the sloping teeth of a wheel

14、or bar, permitting motion in one direction only.2. The pawl, wheel, or bar of this mechanism.,橫紋肌 平滑肌細(xì)粗肌絲比 1:1 15:1 肌小節(jié) 有 無(wú)橫紋