BIO 3303 Lecture 15: LECTURE 15 - BIO3303
30 Aug 2016
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Document Summary
Tropomyosin: double stranded protein spanning ~7 actin monomers, blocks myosin binding sites on actin. Troponin: 3 subunits: tnc: ca2+ binding sites* most important, tni: binds actin* rotates out of the way, tnt: binds tropomyosin. Regulation of actino-myosin binding: ca+ binds to tnc, tni releases actin, troponin-tropomyosin complex moves away from myosin-binding sites, myosin can bind to actin. Mechanism to allow myosin to unattach when the muscle isn"t excited. Black dots represents where myosin binds to actin. Note: active shortening passive lengthening; troponin and tropomyosin are key in allowing muscles to relax. (along with opposing muscle contraction. ) The way they relax and lengthen is by passive means. When muscles are relaxed, need something to lengthen them back out. Speed of contraction and relaxation pattern of cheetahs: super quick. Flying squirrel more postural; holding limbs out, controling precise movements. Motor cortex and other motor control centres send signals through descending tract of spinal cord.
