The reticular formation

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The reticular formation
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Reticular Formation

• loosely arranged neuron cell bodies intermingled
  with bundles of axons
• Various nuclei 1) Nuclei of medullary
  reticular formation
• 2) Nuclei of pontine reticular
  formation
• 3) Nuclei of midbrain reticular
  formation
• It receives and integrates input from all regions
  of the
• central nervous system and processes a great
  deal of neural
• information.

Diffused mass of neurons and nerve fibers forming
an ill-defined meshwork of reticulum in the
central portion of the brainstem.
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THE RETICULAR FORMATION (cont.)

• RF is formed of large number of neurons
• present through the entire brainstem, it
• extends upward to the level of the thalamus
• and downward to be continuous with the
• interneurons of the spinal cord.

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Locations of the reticular and vestibular nuclei
in the brain stem
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THE RETICULAR FORMATION (cont.)

• Afferent projection
• All sensory pathways (general or special
  sensations)
• Cerebral cortex
• cerebellum
• Basal ganglia(corpus striatum)
• Vestibular nuclei, visual pathway
• Thalamus, Subthalamus and Hypothalamic nuclei

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THE RETICULAR FORMATION (cont.)

• Efferent projection
• Reticulobulbar and reticulospinal tracts
• descending pathway to sympathetic and
  parasympathetic outflow of ANS
• cerebellum
• Basal ganglia(corpus striatum)
• Thalamus, Subthalamus and Hypothalamic nuclei

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Connections of Reticular Formation
Fig. 2 Efferent connections of reticular
formation
Fig. 1 -Afferent connections of reticular
formation
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Ascending Reticular Activating System - ARAS
Functional divisions of Reticular Formation

• the reticular activating system (RAS) is an area
  of the brain (including the reticular formation
  and its connections) responsible for regulating
  arousal and sleep-wake transitions.
• Receives fibers from the sensory pathways via
  long ascending spinal tracts.
• Alertness, maintenance of attention and
  wakefulness.
• Emotional reactions, important in learning
  processes.
• Tumor or lesion sleeping sickness or coma.

Fig.3 Brain section.
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Functions

1. Control of skeletal muscles
2. Control of somatic and visceral sensations
3. Control of ANS
4. Influence the biologic clock
5. The reticular activating system
6. Control of endocrine nervous system

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Vestibulospinal and reticulospinal tracts
descending in the spinal cord to excite (solid
lines) or inhibit (dashed lines) the anterior
motor neurons that control the bodys axial
musculature
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• Damage to RF persistent unconsciousness and even
  coma

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Sleep

• Sleep is defined as changed state of
  consciousness from which the person can be
  aroused by sensory or other stimuli, it is
  facilitated by reducing sensory input and by
  fatigue.
• Coma is unconsciousness from which
• the person cannot be aroused.