Types of motor neuron α – motor neuron γ - motor neuron
Types of muscle fibers Extrafusal muscle fibers ( cause muscle contraction supplied by α - motor neuron) Intrafusal muscle fibers or muscle spindle (receptor for stretch reflex, supplied by γ - motor neuron)
DIFFERENCE BETWEEN UPPER & LOWER MOTOR NEURON LESION UMN LESION Paralysis affect movement rather than muscles Muscle wasting is only from disuse, therefore slight. Occasionally marked in chronic severe lesions. Spasticity of clasp- knife’ type. Muscles hypertonic. LMN LESION Individual muscle or group of muscles are affected. Wasting pronounced. Flaccidity. Muscles hypotonic.
Tendon reflexes increased. Clonus often present. Superficial reflexes diminished or modified. Abdominal reflex absent. Babinski’s sign +ve, Increased jaw jerk. Tendon reflexes diminished or absent. Superficial reflexes often unaltered.