Question

A 47-year-old man complains of slowly progressing weakness of both “legs.” On examination he has a flaccid paralysis of both lower extremities, muscle fasciculations, hypotonia, and areflexia. In addition, there is loss of pain and temperature sensations over the anterior aspect of both lower extremities and most of the feet but sparing the little toes.

        19.    The flaccid paralysis, fasciculations, hypotonia, and areflexia in this patient are most likely the result of damage to what structures?

a.	Lateral corticospinal tracts
b.	Posterior (dorsal) roots
c.	Anterior (ventral) horn cells and alpha motor neurons
d.	Reticulospinal/vestibulospinal tracts
e.	Afferent fibers involved in monosynaptic reflexes

Answer 1

When there is a damage or injury to the lower motor neuron,the voluntary actions of the skeletalmuscle system are directly affected resulting in loss of muscle tone,flaccid paralysis,fasciculation and hypotonia.This lower motor neuron together forms the ventral root of the nerve in the spinal cord. . There are three muscle fibres in lower motor neuron alpha (extrafusal muscle fibre) ,beta(both extrafusal and intrafusal)and gamma(intrafusal) motor neuron.The alpha motor neuron innervates the extrafusal muscle fibre and initiating the movement of the skeletal system

Ans:c.Anterior (ventral ) horn cells and alpha motor neuron