describe the physical events of sliding filament theory. (5 marks)
The sliding filament theory explains how the muscle contraction occurs by the interaction between the thick and thin filaments .Sacromeres are the units of muscle tissue having arranged thick and thin filaments. According to this theory the increase in the Ca 2+ initiates the sliding of the filaments, which inturn is switched off due to the decrease in Ca 2+. That is the sarcoplasmic reticulum releases Ca 2+ into sarcoplasm during the initiation of contraction. All the thin filaments which are present on either sides of the sarcomere moves or slide towards the thick stationary filament which is present at the centre. Since the thin filaments slides inwards the sarcomere get shortened and as a result the contraction occurs. The relaxation occurs when there is re uptake of the Ca 2+ into sarcoplasmic reticulum. Due to the break down of the ACh at neuromuscular junction, the action potential of the muscle fibre stops. So the Ca 2+ moves back to sarcoplamic reticulum resulting in the process of relaxation. Some of the main physical changes that can be noticed are;
- Shortening of the sarcomeres.
- Viscosity increases the density of the sarcoplasm.
- Increased tonicity increases the number of motor units to attain the contraction phase.
- Partial conversion of ATP into heat occurs during the muscle contraction.