1. Reticular formation (RF) in the brain stem, nuclei of RF, RAS, function of RS, coma, brain death

2. Reticular Formation and its connections
04/10/2016
Dr. Tibor Wenger

3. Reticular formation: definition
Mass of neurons and nerve fibers extending from the medulla (caudal part) to the midbrain (continuing into the zona inserta and reticular nuclei of the diencephalon)
Organized into definitive nuclei groups having important afferent and efferent connections

4. Positions of the reticular formation nuclei (1)

5. Positions of the nuclei of the reticular formation (2)
Reticular nuclei in the
caudal region of the pontine
tegmentum
Reticular nuclei at the level
of inferior colliculus

6. Nuclei of the reticular formation of the brain stem, rostro-caudal orientation

7. Neurons of the reticular Formation. A: interactions between
dendrites and axon
collaterals of neurons
with asceding (blue)
and descending (red)
Projections.
B: Neuron whose axon
divides into long
ascending and
descending branches
(After Barr and Kiernan: The Human Nervous
System)

8. Connections of the central and lateral groups of the reticular nuclei
(After Barr and Kiernan: The Human Nervous System)

9. The afferent connections of the reticular formation
Sensory systems: practically most of the sensory system (somatic and visceral) projects upon the RF with exception of medial lemniscus
Spinal cord: spinoreticular fibers (mainly from lamina VI-VIII)
Cerebral cortex: from wide areas of both motor and sensory cortex (so called: cortico-reticular tract)
Cerebellum: projections mainly from nucl. Fastigi
Brain stem: lateral hypothalamus, superior colliculus
Basal ganglia: pallidum

10. The efferent connections of the reticular formation 1
Ascending connections Cerebral cortex: few fibers directly, mainly via the diencephalon (thalamus, hypothalamus, subthalamus, particularly intralaminar nuclei (Ascending reticular activating system!)
Locus ceruleus (sleep)

11. The efferent connections of the reticular formation 2
Descending connections: Spinal cord: medial reticulospinal tract, lateral reticulospinal tract Cranial nerve nuclei: practically all nulei of cranial nerves (N. II ?)
Local connections: between different groups of RF’s nuclei

12. Functions of the RF 1
Somatic motor function: both cerebral and cerebellar
via cranial nerve nuclei and lamina IX of spinal cord (modification of alpha and gamma motor neurons: pontine facilitatory, the medullary inhibitory influences)
Somatic sensory function:
selective transmission of sensory impulses
pain!

13. Functions of the RF 2 Visceral motor function:
Medial group: Inspiration,
depressor effects on circulatory system
(hearth rate, blood pressure!)
Lateral group: expiration,
pressor circulatory effects

14. Ascending reticular activation system
(RAS)

15. Functions of RAS Brain death: Irreversible brain (in most cases RAS)
ACTIVATION:Via diencephalic nuclei major role in
arousal and attentiveness, alertness
Improuves learning (wakefulness)
DESACTIVITY: somnolence (sleep!)
coma (not only RF!)
Sensitive to general anesthetics and tranquilizing drugs
Consciousness in brain degenerative diseases
Coma: patient cannot vocalize, has no spontaneous eye movements and no responds reflexlyor no to painful stimuli
Brain death: Unresponsivnes to external stimuli, absence of spontaneous breathing, dilated, fixed pupils, flat EEG, no return from coma(no recognizable reversible cause for the coma)
Brain death: Irreversible brain (in most cases RAS)
damages of respiratory and cardiovascular functions