BioNinja

All muscles contain long protein filaments (myofibrils) which are responsible for muscle contraction and relaxation – however different types of muscles possess specialised features according to their function

• Striated muscles connect to the bones of the skeleton and are responsible for locomotion (voluntary movement)

• Cardiac muscle cells are found within the heart tissue and are responsible for the rhythmic beating of the heart

Striated Muscle Fibres:

• Skeletal muscles are comprised of long, cylindrical fibres that are formed from the fusion of individual cells 
  

• The fibres therefore have a single, continuous plasma membrane (sarcolemma) and are multinucleate
  

• These long and cylindrical fibres are packed together in unbranching strands (typically 2–3 cm in length) that collectively form a muscle bundle 
  

• While the muscle fibre operates as a single functional unit, the fact that it was formed from the fusion of individual muscle cells makes it debatable whether a muscle fibre can be considered a cell
  

Cardiac Muscle Cells:

• Cardiac muscle cells are short (~0.1 mm), narrow and fairly rectangular in shape
  

• Unlike in skeletal muscle, the cardac muscle cells are not fused together and consequently are mononucleated (one nucleus per cell)
  

• The individual muscle cells are connected by gap junctions at intercalated discs, which allow for electrical conduction between the cells
  

• Cardiac muscle cells are branched, allowing for faster signal propagation and contraction in three dimensions
  

• The cells have more mitochondria than striated muscle fibres as they are more reliant on aerobic respiration for ATP production
  

Types of Muscle

Skeletal Muscle

Cardiac Muscle