Question

One effect of caffeine is to increase the level of calcium in the myoplasm of skeletal muscle. This tends to make muscle fibers more responsive to a stimulus so that they generate more force. Describe a reasonable mechanism for this action of caffeine.

Answer 1

Answer: Caffeine is a stimulant of a nervous system. It makes muscle fibres more responsive due to its action on neuro-muscular junction, because it acts upon the ryanodine receptor (Type-1) which causes the release of calcium ions from sarcoplasmic reticulum into the sarcoplasm or muscle cytoplasm. As soom as the myoplasm is flooded with the increased concentration of the calcium ions, so, more calcium will bind to the C-subunit of troponin protein and the change in its conformation occurs. Due to this changed conformation, it exposes the myosin- binding site of actin by removing the tropomyosin. As this site gets exposed, myosin head can bind to this exposed site and this lead to the formation of cross bridge, followed by the power stroke that separated the bound ADP on the myosin head. So, in the presence of caffeine, more calcium will be released and increaded concentration of calcium will increase the number of power strokes which inturn would increase the number of cross bridges formed that signifies the higher force generated.