Termination

All the fibers of pyramidal tracts, either crossed or uncrossed, terminate in the motor neurons situated in anterior gray horn either directly or through internuncial neurons. The axons of the anterior motor neurons supply the skeletal muscles directly by passing through the anterior nerve root. The neurons giving origin to the fibers of pyramidal tract and their axons are together called the upper motor neurons. The anterior motor neurons in the spinal cord and their axons are called the lower motor neurons.

Function

The pyramidal tracts are concerned with voluntary movements of the body. Fibers of the pyramidal tracts transmit motor impulses from motor area of cerebral cortex to the anterior motor neurons of the spinal cord. These two tracts are responsible for fine, skilled movements.

Effects of Lesion

The lesion in the neurons of motor cortex and the fibers of pyramidal tracts is called the upper motor neuron lesion. The following are the symptoms:

1) Voluntary movements: Voluntary movements of the body are very much affected. Initially, there is loss of voluntary movements in the extremities. Later, it involves the other parts of the body like hip and shoulder.

2) Muscle tone. The muscle tone is increased leading to spasticity of muscles. The muscles are paralyzed. This type of paralysis of muscles is called the spastic paralysis. The spasticity is due to the failure of inhibitory impulses from cerebral cortex to reach the spinal cord.

3) Reflexes: All the superficial reflexes are lost. And the deep reflexes are exaggerated. Some pathological reflexes are positive.

4. Materials for auditory self-work.

4.1.List of study practical tasks necessary to perform at the practical class.

Materials and methods: neurologic hammer.

Investigation object: human being.

Task 1. To investigate muscular tone in human being

Muscular tone must be determined by palpation and by passive movements in joints performance. You should determine by palpation the degree of muscular tension. Light tension is observed at normal muscular tone. The students assess the degree of resistance to passive movements by the passive movements performance.

At significant hypotony the movements volume is increased and they are performed without any resistance.

At hypertony passive movements at the first moments of flexion meet with strong (significant) resistance.

Task 2. To investigate surface (skin) reflexes on stretch

1. Abdominal reflexes:

1. superior – it’s caused by puncture irritation of abdomen skin in parallel of rib arc; the reflexes arc is closed at D₆-D₈ segments of spinal cord (from D – dorsal);

2. intermediate – by similar irritation but at horizontal dimension at navel level; the reflexes arc is closed at D₉-D₁₀;

3. inferior- in parallel to groin plica; the reflexes arc is closed at D₁₁-D₁₂.

2. Plantar reflex - is a plantar flexion of foot toes as a response of puncture irritation of external plantar limb; the reflexes arc is closed at L5-S2 and is in sciatic nerve.

At injury of corresponding motor nerve and corresponding link of reflector arc the response reaction is decreased or disappeared (areflexy), muscular atony, atrophy are observed.

Fig. 21