At the end of this presentation, all the students should be able to:
Identify the various pathways for transmission of signals for voluntary motor control from the motor cortex to the muscles
Upper motor neurons (Descending tract)
Extra pyramidal tracts
They are mostly responsible for the involuntary and automatic control of all musculature, such as muscle
tone, balance, posture and locomotion.
Red nucleus present in midbrain receive signals directly from primary motor cortex and also corticospinal tract.
Red nucleus also contain neurons similar to betz cell(pyramidal cells) present in motor cortex.
Neurons of red nucleus contain greater number of dynamic neurons which excited at higher rate for shorter period of time at beginning of contraction and cause rapid development of force.
Importance: Red nucleus works with cerebellum and cerebellum play an important role in rapid initiation of muscle contraction.
- Fibers of this tract arise from red nucleus in midbrain.
- Then fibers cross the midline and descend through the reticular formation of pons and medulla.
- Lies in lateral column of spinal cord.
- Then terminate in the interneurons and or anterior motor neurons of the spinal cord up to thoracic segments along with lateral corticospinal tract(together form lateral motor system of cord).
- Help in contraction of flexor muscles of upper limb(not the fine movement).
Flexion of upper limb
Has two types of fibers:
- Medial reticulospinal fibres(Pontine reticular tract)
- Lateral reticulospinal fibres (Medullary reticular tract)
Medial Reticulospinal fibres:
Lateral reticulospinal fibers:
Functions of Reticulospinal tract:
Reticulospinal tract is concerned with:
- Control of movements of muscles
- Maintenance of muscle tone
::Pontine and medullary fibers have opposite effects on these functions.
Anterior vestibulospinal tract
- Integrate head and eye movements, so ultimately help in maintain gaze.
- During head movement, eyes move in opposite direction and maintain image in center of visual field.