Kinesiology 2230A/B Lecture Notes - Lecture 26: Myosin Head, Too Short, Sarcomere

• School: Western University
• Department: Kinesiology
• Course: Kinesiology 2230A/B
• Professor: Glen Belfry

Document Summary

Without release of ca+, no contraction occurring, extensive network of tubular channels to myofibrils, each tubule terminates in a saclike vesicle that stores ca, depolarization --> release of ca+ --> activates actin filaments. Muscle triad: on both sides of a t-tubule are dilated end sacs of the sarcoplasmic reticulum called the terminal cisternae. A t-tubule, together with its two terminal cisternae, is called a muscle triad. Sliding filament hypothesis: distance between actin gets shorter. I band: looking at proximal ends closest to the z-line of the myosin. Since the actin is moving to(cid:449)ard each other, the (cid:373)yosi(cid:374) does(cid:374)"t (cid:373)o(cid:448)e (cid:373)uch. Distance between z-line and proximal ends of myosin is going to decrease as the muscle conract: a- band: length of the myosin itself. Distance does not change: h- zone: distal ends of actin. Mechanism for myosin- actin interaction: ca+ released from sarcoplasmic reticulum. Moves the tropomyosin away from the binding sites for the myosin heads.