- Muscles along with bones enable us to move and perform different activities
- The cells are elongated and are called muscle fibres
- The movement is possible due to special proteins called contractile proteins
- The proteins contract and relax to cause movement
Based on the types of movement and where they are present, the muscles are of different types.
- Muscle cells are long, cylindrical, unbranched and multinucleate (having many nuclei).
- Such muscles which we can move if we like to and control the movement is called voluntary muscle.
- Since these are mostly attached to bones and help in movement (for example movement of limbs), they are also called skeletal muscles.
- When stained appropriately and observed under the microscope, they have alternate dark and light bands or striations . Thus they are called striated muscles.
Can you control the movement of muscles in our digestive system or the movement of your lungs ?
The movement of some muscle groups cannot be controlled by us and they are called involuntary muscles .
A few more example include:
- Contraction and relaxation of blood vessels
- Muscles in iris of the eye
- Muscles in ureters
- Muscles in the bronchi of the lungs
The cells are spindle-shaped (long with pointed ends) and uninucleate (having a single nucleus).
They have a rather smooth appearance and do not have dark and light striations when observed under the microscope.
Hence they are also called Smooth muscles or Unstriated muscles .
- The muscles in the heart are also involuntary, we cannot control the movement
- However, the muscle tissue in the heart is different from other involuntary muscles
- Heart muscle cells are cylindrical, branched and uninucleate. They have striations .
- These involuntary muscles are called cardiac muscles and bring about contraction and relaxation of walls of the heart .