Understanding Motor Units: The Building Blocks Of Muscle Movement

Understanding Motor Units: The Building Blocks Of Muscle Movement

Question 1. Motor unit.
Answer:

Motor unit Definition:

• Each ventral horn cell along with its motor nerve is called motor neuron.
• The single motor neuron, its axon terminal and the muscle fibers innervated by it are together called motor unit.

Motor unit Properties:

1. The number of muscle fibers in a motor unit varies inversely with the precision of the movement performed by the part.
   • The number of muscle fibers is small in the motor units of the muscles controlling fine, graded and precise movements.
   • The muscles concerned with coarse movements have motor units with large number of muscle fibers.
2. All the muscle fibers in a motor unit are of same type.
3. Depending on the type of muscle fibers, they innervate, motor units are of two types slow and fast.
4. Recruitment of motor unit.
   • With minimal voluntary activity of muscle a few motor units are discharge and with increasing voluntary efforts more motor units are put into action.
   • This process is called recruitment of motor units.
5. The graded response in the muscle is directly proportional to the number of motor units activated.

Question 2. State the difference between voluntary and involuntary muscles.
Answer: