Muscle fibre cells are a great example of how animal cells can be highly specialised for their function. In this article we will look at the structure of muscle fibre cells and how it relates to their function.
Muscle fibre cells – structure and function
The below diagram shows a cross-section of a muscle fibre cell, with one of the myofibrils extended to show the actin and myosin filaments.
- Some muscle fibre cells have many mitochondria to provide ATP in aerobic respiration for muscle contraction. (Fast twitch fibres don’t – read more here).
- The sarcolemma is the cell-surface membrane. It is depolarised if acetylcholine is released at neuromuscular junctions.
- The depolarisation is spread into the cell via the T-tubules.
- The sarcoplasmic reticulum stores and releases calcium ions which are needed for contraction.
- Muscle fibre cells are multinucleate (they have more then one nucleus), because they are large cells originally formed from fusion of many cells.
- The sarcoplasm is the cytoplasm.
- The cells contain many specialised organelles called myofibrils. These consist of two main protein filaments: actin and myosin. These filaments slide over each other during muscle contraction.
- There are many capillaries nearby to provide oxygen and glucose for aerobic respiration.
Note that this is a skeletal muscle fibre cell. There are different types of muscle in the body e.g. smooth muscle and cardiac muscle. We will look at these different types of muscle in a future article.
Summary
- Muscle fibre cells are highly specialised for muscle contraction. Muscle contraction requires ATP, calcium ions and protein filaments, all of which the cells are adapted to provide.
- The prefix “sarco” is often used for different parts of muscle cells.
