Download General somatic motor nuclei

 What
is the Reticular
Formation ?
• Reticular Formation
Diffused mass of neurons and nerve fibers forming an ill-defined
meshwork of reticulum in the central portion of the brainstem.
 Various nuclei: 1) Nuclei of medullary reticular formation
2) Nuclei of pontine reticular formation
3) Nuclei of midbrain reticular formation
 Situated: - Downwards into spinal cord
- Upwards up to thalamus and subthalamus
Connections of Reticular Formation
Fig. 1 -Afferent connections of
reticular formation
Fig. 2 – Efferent connections
of reticular formation
Functional divisions of Reticular Formation
Ascending Reticular Activating System - ARAS
 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 lession – sleeping
sickness or coma.
Fig.3 – Brain section.
Reticular Formation



Extends throughout
brainstem
loosely organized neurons,
outside of the major nuclear
groups of the brainstem.
Participate in widespread
connections
Reticular formation





Phylogenetically oldest part of brain
Diffuse net-like meshwork (reticulum)
Functions: homeostasis, consciousness, arousal,
pain, primitive motor control, muscle tone,
Vital centers in medulla and pons: cardiovascular,
respiratory, homeostatic
Ascending reticular activating system (ARAS)
originating from midbrain RF: diffuse cortical
projections- consciousness, lesions lead to coma
Reticular formation
3 ZONE
 • Raphe nuclei
 • Medial zone nuclei
 • Lateral zone nuclei

Medial zone Lateral zone
Raphe Nuclei
Midline - bilaterally
Found at all 3 levels of
brainstem
Neurotransmitter used is
serotinin
Projections
Rostrally - active in
sleep program
Caudally - modulates
pain perception
Raphe Nuclei

Raphe nuclei of medulla




Raphe nuclei of the pontine reticular formation



Nucleus raphe obscurus (nucleus raphe obscurus)
Nucleus raphe magnus (raphe magnus)
Nucleus pallidus (raphe pallidus)
Pontine raphe nucleus (raphe pontis)
Inferior central nucleus
Raphe nuclei of the midbrain reticular formation


Superior central nucleus (nucleus centralis superior)
Dorsal raphe nucleus (nucleus raphe dorsalis
Raphe
Nuclei
P A I N

periaqueductal gray and Raphe
nucleus Magnus

Stimulation of periaqueductal
gray activates Raphe nuclei Outflow to spinal cord, synapses
on interneurons in Lamina II
(substantia gelatinosa) & III

endorphins : regulate pain
perception & induce analgesia
Descending
connections
(A) to the dorsal horn, and from
there

(B) to the periaqueductal grey
(PAG).

Descending impulses pass
(C) to the raphe nuclei,
especially the nucleus raphe
magnus, in the upper
medulla,

reticulospinal fibres (D).
Central group






Central medullary n
Gigantocellular n.
Oral and caudal
Cunieform
Subcuniform
PPRF
Paramedian Pontine Reticular
Formation (PPRF)

mediate the horizontal
eye movements on

their ipsilateral sides.
innervations from the superior
colliculus and from the frontal
eye fields via frontopontine
fibers.
Gigantocellular reticular
nucleus
giant neuronal cells
excites the hypoglossal
nucleus, and can play a role in
the actions of the said nerve
expiration (or outbreathing) along with the
parvocellular nucleus
2
1
Lateral reticular nucleus



Reticulocerebellar tract
and spinal cord
Motor systems
movement, ocular
movement, posture
Magnocellular reticular nucleus
(lateral )

inspiration (in-breathing) with
a part of the ventral r. nucleus



(learning / memory?)
projections to the vermis of
the cerebellum. The rest sends to
the hemisphere
most input from the spinal cord is
relayed into the vermis
PMRN : paramedian reticular
nucleus




Reticulocerebellar tract
connections to the spinal
cord in a mostly ipsilateral
manner
projects to the vermis in
the anterior lobe, the
pyramis and the uvula
stereotyped of motion
Cholinergic neurons
‫در حرکات کلیشه ای‬
‫و هوشیاری‬
catecholamine nuclei
Locus ceruleus

Melanin
granules = blue
color;( nucleus
pigmentosus
pontis),
Locus ceruleus


mediating arousal
to be activated by
stimuli.
modulate pain
through pathways
that descend to the
spinal cord

2.1 Afferent connections from


- Spinal cord - Basal ganglia
- Cranial nerve nuclei - Cerebral cortex
- Cerebellum
- Subthalamus, hypothalamus & thalamus

2.2 Efferent connections to

- Spinal cord - Basal ganglia
- Cranial nerve nuclei - Cerebral cortex
- Cerebellum
- Subthalamus, hypothalamus & thalamus





parvocelular nuclei
PVN : parvocellular reticular formation

expiration with a part of

the gigantocellular
nucleus
innervate the
mesencephalic
trigeminal nucleus and
the facial, hypoglossal
nuclei

control feeding reflexes
parabrachial nuclei



Taste fiber reley
kolliker fuse
(respiration rhytem
regulation
Nucleus of Darkschewitz


Periaqueductal gray
Vertical eye
movement
Vertical conjugate
Gaze Center
Rostal interstitial
nucleus of MLF
Horizontal conjugate
Gaze center
Interstitial Nucleus of Cajal
•ocular movement
related to vertical (up or down) eye
position and saccades
Oculomotor & Trochleai nuclei
group of neurons located ventrolateral
to the hypoglossal nucleus
Basal Forebrain
•Stimulating the basal forebrain gives
rise to EEG sychrony and sleep.
•located near the sub-arachnoidal
space.
Ach
ventral to the lentiform nucleus
•Basal Forebrain
•includes the septal
nuclei and the
basal nucleus of Meynert.

Cortical ACh release during waking and
rapid eye movement (REM)

reduced during non-REM (NREM) sleep.

Loss of basal forebrain cholinergic neurons :
sleep disruption
THANK YOU