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13b reticular pathways - Coggle Diagram
13b
reticular pathways
The afferent and efferent connections of the RF form several pathways.
Cortico-reticulospinal pathways
Afferents of this pathway to neurons of RF come from the motor and
other areas of cerebral cortex.
Areas of reticular formation which receive impulses from the cerebral cortex are:
Bulbo-reticular inhibitory area
located in the lower part
of the medulla,
Bulbo-reticular facilitatory area
located in the pons
Cortico-reticulo-cerebellar and
cortico-reticulo-basal ganglia
connections
Some afferents from cerebral cortex,
after relaying in reticular formation
project to the cerebellum and basal ganglia.
Cerebello-reticular connections,
Visceral control pathways and
Certain centres in the
reticular formation regulate
respiration,
heart rate and
blood pressure.
These effects are mediated through connections
between the reticular formation and autonomic centres in the brainstem & SC,
but the pathways concerned are not well defined.
Reticular activating system (RAS).
Reticular activating system (RAS) also known as ascending reticular activating system (ARAS)
is a complex polysynaptic pathway that
projects diffusely from the brainstem
reticular formation to the cerebral cortex.
Collaterals to RAS funnel from the following sources:
Long, ascending sensory pathways
such as spinothalamic tracts
are the important sources of collaterals to RAS. The fibres of the tracts, which
convey
slow pain
, send the richest collateral connections to the RAS.
collateral to the RAS also funnel from the
trigeminal,
auditory,
visual and
olfactory pathway systems.
Efferent projections from RAS are:
Majority of RAS fibres
end in nonspecific thalamic nuclei
(intralaminar and midline nuclei),
and from there are projected
diffusely and nonspecifically to the
whole neocortex.
Another part of RAS .
bypasses the thalamus
to project diffusely
to the cortex
The RAS fibres occupy the
core portion of the brainstem.
Whereas the specific fibres occupy the
lateral parts of the brainstem.
RAS-core
sp fibers- lateral parts
Stimulation of RAS.
The reticular activating system (RAS) is stimulated by impulses
funnelled into it through the collateral described above.
t
he spinothalamic pathway and trigeminal and etc
Thus, the RAS is a nonspecific system
which can be
excited by
any sensation.
Whereas, the classic sensory pathways are specific in that the fibres in them are
activated by only one type of sensory stimulation.