LSB258 Lecture Notes - Lecture 5: Sarcomere, Cardiac Pacemaker, Endomysium
Document Summary
Skeletal muscle structure at molecular level: skeletal muscle appears striated or striped. Energy released used to convert myosin to high-energy form; ca 2+ is present, cross bridge cycle continues. Latent period: contraction phase; ca 2+ release exceeds reuptake, relaxation phase; ca 2+ reuptake exceeds release, twitches may vary from one muscle or muscle cell to another, diameter. Force produced by individual muscle fibres depends on two main factors: number of muscle fibres contracting. Force generated in individual muscle fibres --> number of active cross bridges; dependent on three further factors: number of active cross bridges (and muscle force) depends on: Frequency of stimulation; individual twitches/ contractions only occur at low stimulation frequencies -->relaxation defends on the balance of ca 2+ release and uptake. Fibre diameter; number of thick and thin filaments per unit cross sectional area does not differ greatly between muscles. Muscles with more sarcomeres in parallel (i. e. greater diameter) produce more force; hypertrophy: change in fibre (sarcomere) length.
