Reticular formation in control of motor functions

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Reticular formation in control of motor functions

  1. 1. RETICULAR FORMATION IN CONTROL OF MOTOR FUNCTIONS
  2. 2. 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
  3. 3. MOTOR CONTROL. RETICULOSPINAL TRACT Reticulospinal tract extends from reticular formation to the spinal cord. It has two parts:  Medial (pontine) - MRST;  Lateral (medullary)- LRST
  4. 4. 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
  5. 5. 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.
  6. 6. 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
  7. 7. 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
  8. 8. EFFECTS It is responsible for:  tone,  balance,  posture, especially during movement.
  9. 9. THE EFFERENT CONEXIONS OF THE RETICULAR FORMATION The 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
  10. 10. 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.

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