6. Muscle Structure and Contraction Flashcards
Name the layers of a muscle fibre from outside in
Epimysium
Perimysium (surrounds fascicle)
Endomysium
Muscle fibre
What is the H zone?
Myosin with no actin
Bisects the A band
What is the I band?
Actin with no myosin
What is the A band?
Entire length of myosin, including the area overlapping actin
What is a sarcomere?
Until of a myofibril contained between 2 Z lines
What is the M line?
Bisects the H zone
What are accessory proteins?
Maintain structure of muscle
What does alpha-actinin do?
Maintains actin lattice
What does dystrophin do?
Anchors the actin filaments to the sarcolema
What are triads made up of?
2 cisternae tubules
Transverse tubule
Where are triads found?
Junction of A and I bands
What do t-tubules do?
Brings action potential into interior of muscle fibre
What is the function of ryanodine receptors?
Ion channel responsible for the release of Ca++ from the sarcoplasmic reticulum
What is a dihydropyridine receptor?
Protein which senses the depolarisation of the T-tubule
Describe the process of muscle contraction
- Myosin head attaches to actin myofilament, forming a cross bridge
- Phosphate generated in the previous cycle is released, initiating the power stroke
- Myosin head pivots and bends as it pulls on the actin filament, sliding it towards the M line
- ADP is released
- When ATP attaches to the myosin head, the link between the myosin and actin weakens and the cross bridge detaches
- When ATP is split the myosin head is energised
