RETICULAR FORMATION IN CONTROL OF MOTOR FUNCTIONS

RETICULAR FORMATION IS THE CENTRAL CORE OF THE BRAINSTEM  

Extends from the rostral midbrain to the caudal medulla.

Reticular formation is concerned with the locomotor control not only through its direct reticulospinal projections to lower motor centers, but indirectly, by influencing the activities of the cerebellum, red nucleus, substantia nigra, subthalamic centers, the corpus striatum and the cerebral cortex

MOTOR CONTROL. RETICULOSPINAL TRACT

Reticulospinal tract extends from reticular formation to the spinal cord.

It has two parts:

Medial (pontine) - MRST;

Lateral (medullary)- LRST

MOTOR CONTROL. RETICULOSPINAL TRACT

Medial (pontine)- MRST;

The fibers of this tract arise from the caudal pontine reticular nucleus and the oral pontine reticular nucleus and project to the lamina VII and lamina VIII of the spinal cord

MOTOR CONTROL. RETICULOSPINAL TRACT

Lateral (medullary)- LRST

The fibers of this tract arise from the medullary reticular formation, mostly from the gigantocellular nucleus, and descend the length of the spinal cord in the anterior part of the lateral column. The tract terminates in lamina VII mostly with some fibers terminating in lamina IX of the spinal cord.

CONTROL OF SKELETAL MUSCLE

Modulate muscle tone and reflex activity: Through the reticulospinal and reticulobulbar tracts, the reticular formation can the activity of the alpha and gamma motor neurons.

Reciprocal inhibition

Maintaining the tone of the antigravity muscles when standing: assisted by the vestibular apparatus of the inner ear and the vestibular spinal tract.

Control of the respiratory muscle

CONTROL OF SKELETAL MUSCLE   Controlling the muscles of facial expression when associated with

emotion: For example, when a person smiles or laughs in response to a joke, the motor control is provided by the reticular formation on both sides of the brain. The descending tracts are separate from the corticobulbar fibers.

During movement, signals pass from the brain's cortex, via reticular formation and spinal cord (pathway A), to muscles, which contract. Other signals pass, by pathway B, to the basal ganglia; these damp the signals in pathway A, reducing muscle tone so that movement is not jerky. Dopamine, a nerve transmitter made in the basal ganglia, is needed for this damping effect. Another transmitter, acetylcholine, inhibits the damping effect

EFFECTS

 It is responsible for:

tone,

balance,

posture, especially during movement.

THE EFFERENT CONEXIONS OF THE RETICULAR FORMATIONThe efferent conexions of the reticular formation are:

Autonomic and locomotor control centers and interneuronals points of spinal cord via the reticular spinal tracts

By short desdcending pathways to similar centers in the brain stem

To the cerebellum

To the red nucleus, substantia nigra and tectum of the midbrain

To numerous nuclei in the subthalamus, thalamus and hypothalamus

 Indirectly through radiations of the later diencephalic nuclei to the corpus striatum and to the cerebral cortex, including most regions  of the neocortex and many areas of the limbic system

RETICULAR FORMATION

Reticular formation convergent information channels from all the principal parts of the nervous system, in turn it projects directly or indirectly back on these regions.

It is essentially involved in all the major functional activities of the nervous system.