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FUNCTIONAL COMPONENTS AND ORGANIZATION
OF SPINAL CORD AND BRAINSTEM
Cross-section of embryo:
Neural crest neuroectoderm
Neural fold
Neural crest
Notochord
Neural crest
Dorsal root ganglion
Surface ectoderm
Neural canal
Neural tube
Formation of basal and alar plates of neural tube
Alar plate
(Sensory
projection neurons
of gray matter)
Basal plate
(Motor neurons
of gray matter)
(White
matter)
Definitive structures from alar and basal plates in spinal cord
(from alar plate)
Spinal nerve
(from basal plate)
Sensory projection neuron =
Alar and basal plates in brain
• Only found in medulla, pons, and midbrain
• Separated by sulcus limitans
• Form sensory and motor nuclei of cranial nerves
III – XII
– Sensory nuclei lateral
– Motor nuclei medial
Cross-section of myelencephalon:
Sensory cranial nerve nuclei lateral
Motor cranial nerve nuclei medial
Sensory
Motor
Sensory
Motor
SPINAL CORD DEVELOPMENT: NOLTE
GSA
GVA
GVE
GSE
BRAINSTEM DEVELOPMENT: NOLTE
GSA
GVA
GVE
GSE
COLUMNS OF NUCLEI IN BRAINSTEM: NOLTE TEXTBOOK
SSA
GSA
SVA
GVA
GVE
SVE
GSE
SVE, SVA, SSA NUCLEI DEVELOP AS COLUMNS IN
BRAINSTEM
COLUMNS OF NUCLEI IN BRAINSTEM: GREY’S ANATOMY
SSA
GSA
SVA
GVA
GVE
SVE
GSE
NOLTE; NUCLEI MIGRATE BUT MAINTAIN SAME GENERAL ORGANIZATION
COLUMNS OF CELLS IN BRAINSTEM
Appendix:
Embryonic development of cranial sensory
and motor cell columns in the Brainstem
Embryonic Development of the Medulla
Alar
Plate
• The myelencephalon develops into
a closed medulla and an open
medulla.
• In the closed medulla:
Some cells in the alar plate
migrate to the marginal zone to
form the nuclei of gracilis and
cuneatus.
• In the open medulla:
The ventricle opens up and
stretches the roof plate becoming
very thin. The brain wall moves
laterally: the alar plate is situated
lateral to the basal plate.
Inf. Olivary Nu
Alar Plate gives rise to
Sensory Relay Nu.
Alar plate is pushed
lateral to basal plate,
and separated by
sulcus limitans.
Sulcus Limitans
GVE
Basal Plate
gives rise to
Motor Nu.
I
O
N
ALAR PLATE gives rise to Nu. Gracilis, Nu. Cuneatus, Inferior
Olivary Nu. and 4 Sensory Cell Columns
• GVA (General visceral afferent) –Caudal Solitary nucleus receives
sensory inputs from mucous membrane of pharynx and larynx, aortic
arch/body and carotid sinus/body (VII, IX, X).
• SVA (Special visceral afferent) –Rostral Solitary nucleus receives taste
sensation from tongues, pharynx and larynx, and epiglottis (VII, IX, X).
• GSA (General somatic afferents)-Spinal Trigeminal Nucleus receives
pain, temperature, and touch sensation from ipsilateral face, ear and neck
areas (V, VII, IX, X)
• SSA (Special somatic afferent )-Vestibulo-cochlear nuclei receive input
from inner ear for vestibular and auditory nerves (VIII).
BASAL PLATE gives rise to 3 motor cell columns
• GSE (general somatic motor)--Hypoglossal Nu. For CN XII.
• SVE (special visceral [branchial] motor) – Nu. Ambiguus, for CN 9, 10,
(cr.11) and innervating muscles of branchial arches. This cell column
migrates to the deep lateral tegmentum.
The spinal accessory Nu./Nv (CN 11) somehow is also put into SVE.
• GVE (general visceral motor)—Inferior salivatory Nu of IX and Dorsal
motor nucleus of vagus, represent the preganglionic neurons of
parasympathetic CN 9 and 10, respectively; they innervate the
postganglionic neurons for the parotid gland (IX), GI and pulmonary
viscera (X), respectively. The GVE to the heart, however, is incorporated
into the SVE (nucleus ambiguus).
Review: Connecting Cranial Nerve
Functional Components to Central Nuclei
Basal Plate (Motor Nu)
CN#
1
GSE
GVE
SVE
2
3
4
5
6
7
8
9
10
11
12
Alar Plate (Sensory Relay Nu)
GSA
GVA
SVA
++
SSA
Forebrain
++
Mesencephalic Nu V
++
++
++
Midbrain
++
+ ++ +
Chief Sensory Nu V
++
Sup. Salivatory
Pons
++
++
++
++
++
++
Inf. Salivatory
D- Motor Vagus
++
++
++
++
++
+++
++
Cr+ Sp++
++
++
++
++
Spinal Trigeminal Nu V
Ambiguus Nu
Medulla
Solitary Nu