VPB 121: Veterinary Physiology - II (2+1)

MOTOR END PLATE

• The axon terminals of the motor neurons innervate each muscle cell. The innervation ratio is the number of muscle fibers or cells innervated by a single motor neuron (motor unit).
• In muscles where delicate control is required the innervation ratio is small (3 to 6) as in extrinsic eye muscles. In the muscles of limb where the fine control is not necessary innervations ratio may be as high as 1000.
• The muscle cell plasmalemma at the motor end plate has got large numbers of infoldings - 0.5 to 1 μm deep 50 – 100 nm width.
• The axon terminal (contains 1,00,000 synaptic vesicles) sends finger like processes into these infoldings but they remain separated by a space of 40 – 60 nm.
• The nerve impulse propagated along the motorneuron and its axon collaterals reaches the neuromuscular junction.

Motor end plate or neuromuscular junction