e.learning R.F.
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Transcript of e.learning R.F.
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RETICULAR FORMATION,
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Reticular Formation
Various nuclei: 1) Nuclei of medullary reticularformation
2) Nuclei of pontine reticular formation
3) Nuclei of midbrain reticularformation
within the meshes of this reticulum are located functionally associated nervous
structures which are vestibular nucleus, red nucleus and subthalamic nucleus.
Situated: - Downwards into spinal cord- U wards u to thalamus and subthalamus
Diffused mass of neurons and nerve fibers forming an ill-definedmeshwork of reticulum in the central portion of the brainstem.
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RETICULAR FORMATION AFFERENT & EFFERENTCONNECTIONS OF RETICULAR FORMATION
ReticularFormation
ReticularFormation
Cerebellum
RedNucleus
Thalamus,Hypothalamus
SC
CortexSubstancia Nigra
Tectum
EFFERENT CONNECTION TOTHE RETICULAR FORMATION
AFFERENT CONNECTION TOTHE RETICULAR FORMATION
Cortex
Thalamus
CorpusStriatum
Cerebellum
SC
SensoryPathways
(Touch, pain,
temperature,kinesthesticsensation)
Optic, auditoryolfactory andtastepathways
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Reticular neurons are classified into:
- sensory neurons
- Motor neurons
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Sensory neuron Motor neurons
Small in size Large in size
Large in number Small in number
Receive impulses from;Lemniscal pathways in brain
stem (medial, lateral,trigeminaland spinal lemnsci)
Olfactory pathway-vestibular
apparatus-cerebral cortex-cerebellum-hypothalamus
Receive impulse from sensoryneurons.
They are 2 types:
Facilitatory reticular formation(FRF)
Inhibitory reticularformation(IRF)
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reticular formation Divided into two branches
ASCENDING RETICULARACTIVATION SYSTEM
DESCENDING RETICULARACTIVATION SYSTEM
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DESCENDING RETICULAR ACTIVATION SYSTEM - DRAS
INHIBITORY (gives origin to
crossed lateral reticulospinal tract.)
Smoothness and accuracy ofvoluntary movements;
Reflex movements;
Regulates muscle tone;
Maintenance of posture;
FACILITATORY (gives origin tothe uncrossed medial
reticulospinal tract )
maintains the muscle tone;
Facilitates autonomic
functions;
Activates ARAS.
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ASCENDING RETICULAR ACTIVATION SYSTEM -ARAS
Receives fibers from the
sensory pathways via longascending spinal tracts.
Extends upward as reticularactivating system (RAS) that
relays in non specificthalamic nuclei (intralaminarand midline nuclei) thenthalamic radiation arises
toward the cerebral cortex.This pathway is calledreticulo-thalamocorticalpathway
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Ascending Reticular Activating System - ARAS
Functions:
Alertness, maintenance of attention and wakefulness.
Emotional reactions, important in learning processes.
It controls the ability to filter out information from external sourcesand focus on one particular fact, detail or thought .
It is responsible for providing an integrated (cardiovascular,respiratory and motor) response to external stimuli.
The Reticular Activating System is the attention center in the brain.It is the key to "turning on your brain," and also seems to be thecenter of motivation.
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Factors affecting activity of RAS
Factors increasing the activityof RAS
Impulses from sensory,motorpathways.
Stress
Sympathomimetic drugs
Caffeine
Thyroid hormone
Factors decreasing the activityof RAS
Decreased sensory input
Impulses from sleep centers
Anesthetic drugs
Tumor that destroy thissystem
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