UTH MS1 DEVO: Block 2:3 Neuro devo/new
NEURAL TUBE DEFECTS:
...
NEURO DEVO
...
NEURO II
...
The caudal _____ of the neural plate becomes the spinal cord.
1/3
The cortex of embryo is still smooth at week
14
Cortex begins to develop major sulci and gyri by week
26
Sympathetic chain ganglia derived from spinal neural crest cells, and in cervical region, only ____ ganglia form and in coccygeal region, there is ____ chain ganglia.
3 cervical ganglia, 1 coccygeal chain ganglia.
Cortex has developed most of major sulci and gyri by week
30
by the end of cortical development, there are ___ layers, the ____ layer becomes white matter, and layer ___ developed first.
6 layers, the intermediate layer becomes white matter, and layer 6 developed first
The hindbrain has ____ segments called _______ that are specified according to the expression patterns of HOX genes.
8 rhombomeres
Alar plate is a collection of nerve cell bodies in the CNS (Nuclei) that make up dorsal gray matter. Receive and relay input from _________________.
Afferent (sensory, somatic, visceral) neurons (top light blue)
Basic organizing feature of the spinal cord are the ________.
Alar and basal plates.
The cerebellum arises largely from extension of ______ plate of _____cephalon.
Alar plate of Metencephalon
The two organizing centers of the forebrain develop from the anterior neural tube:
Anterior neural ridge (ANR) and second organizing center
In subventricular zone, you can keep getting neurons and oligodendrocytes developing, but they come from ____ instead of radial glial cells.
B cells that make intermediate precursors.
What morphogen determins the dorsal-ventral axis of the spinal cord?
BMP (dorsal, sensory) and SHH (ventral, motor)
What links the cerebral hemispheres?
Commisures (bands of neural tissue connecting hemispheres) and corpus callosum (by week 6) if don't link, not compatible with life.
The three major inter-hemispheric pathways:
Corpus callosum, and anterior & posterior commissures.
Neurogenesis of cerebellum: the ventricular zone becomes the internal germinal layer, which produces neuroblasts that form the...
Deep cerebellar nuclei, primitive purkinje neuroblasts, golgi neuroblasts AND GLIOBLASTS (--> macroglia, astrocytes and oligodendrocytes)
Cranial nerve II is the only CN associated with
Diencephalon All the others (lower down! like on the brain from anatomy lab. mostly associated with medulla)
Cerebral hemispheres end up growing so much they cover the
Diencephalon (thalami), mesencephalon (midbrain), and rhombencephalon (hindbrain)
*Just like the spinal cord, the morphogen ____ is at a higher concentration on the dorsal side and the morphogen ____ is at a higher concentration on the ventral side of the brain
Dorsal: BMP Ventral: SHH
each spinal nerve (mixed) splits into dorsal and ventral primary rami; dorsal to innervate _____ and ventral to innervate _____.
Dorsal: epiaxial muscles (deep muscles of back) Ventral: hypaxial muscles (diaphragm, abdominal muscles, limb muscles)
Second organizing center secretes FGF 8 too, but between midbrain and hindbrain. There it induces expression of... which..
EN1 and EN2, differentiates midbrain and cerebellum
Pituitary gland: duel development: anterior lobe origins:
Ectodermal placode on roof of stomodeum invaginates to form RATHKE's POUCH, and grows dorsally. It loses attachment to stomodeum and cells on outside make into anterior pituitary (adenohypophysis). posterior surface= pars intermedia of adenohypophysis.
After glioblasts differentiate, the ventricular layer forms the __________ of the ventricles and central canal of the spinal cord.
Ependymal cell lining
The anterior neural ridge forms at the most cranial border of the neural plate. growth factor _____ induces expression of transcription factor ____ to differentiate the telencephalon.
FGF8, FOXG1
ANR secretes FGF 8 at cranial border of neural plate, and induces expression of ... which...
FOXG1, plays a key role in differention of telencephalon.
The Metencephalon's adult derivative is the
Pons and cerebellum
Neuroblasts can no longer divide and is differentiated because it has formed...
Processes: primitive axon and dendrite.
The three types of cortical development disordersare
Proliferation/apoptosis, migration, organization
Neural crest cells in each rhombomere migrate to specific locations in the embryo:
R1-2--> phar arch 1 R4--> phar arch 2 R6-7--> phar arch 3
excitatory neurons do ____ migration inhibitory neurons do ____ migration
Radial tangential
SHH induces the paraxial mesoderm to differentiate into
Sclerotome (which becomes vertebrae) and Dermomyotome (which becomes skin and epiaxial/hypaxial muscles)
Sulcus limitans
Shallow, longitudinal groove left in lateral walls of neural tube. Separates developing gray matter into dorsal alar plate and ventral basal plate. Runs length of spinal cord through mesencephalon.
Special visceral afferents:
Smell and taste!
The spina bifida in which meninges or spinal cord protrudes through a vertebral arch that failed to fuse is called
Spina bifida cystica Usually causes hydrocephaly too, because CSF can't circulate well. 3 types
The spina bifida in which vertebral arches (usually L5 or S1) fail to fuse= incomplete vertebral arch, is called
Spina bifida occulta Usually see little dimple and tuft of hair there.
Spina bifida cystica: Meningocoele
Spinal cord in normal spot, but meningeal sac protrudes through defect.
There are two places of adult neurogenesis:
Subventricular zone and hippocampus.
The alar plate of the mesencephalon gives rise to the
Superior colliculi (vision) and inferior colliculi (audition)
Prosencephalon, during week 5, divides into the :
Telencephalon and the diencephalon
The diencephalon's adult derivative is the
Thalami: Thalamus, hypothalamus, and epithalamus
Spina bifida is a defect in ...
The closure of the caudal neuropore.
Which layer of the cerebral cortex is the oldest?
The inside most layer. (inside out migration in cortical plate)
What is the marginal layer of developing spinal cord?
The outer white matter layer. increases in mass because of addition of different axons and incoming dorsal root sensory fibers
corpus callosum connects
The two cerebral hemispheres.
Thalamus grows and closes off the ___ ventricle by fusing together
Third
The neural canal in each vesicle becomes a definitive, distinct ______ in the future brain:
Ventricle
Hydrocephalus
abnormal accumulation of CSF. blockage of aqueduct. Enlarged head of baby and high pressure
Pontine flexure:
aka dorsal flexure. Forms between metencephalon and myelencephalon splits the walls of myelencephalon --> thinned roof of fourth ventricle. Helps in development of cerebellum and pons.
Cephalic flexure:
aka mesencephalic, midbrain. At level of future midbrain and persists in adult as the bend between brainstem and forebrain
What is the defect in which the rostral ("cranial") neural tube never closed?
anencephaly, cranioraschischisis.
The body of the medulla becomes flat on the ____ side.
anterior
Mesencephalon's neural canal becomes
aqueduct of sylvius
Cerebellum has three parts:
archicerebellum (vestibular system) Paleocerebellum (sensory function) Neo-cerebellum (control of movements)
The lumen of the neural tube is reduced to a small ______.
central canal --> neural canal.
By day 25 of development, the hindbrain has developed into 8 rhombomeres, and the rhombencephalon (hindbrain), which divides into the metencephalon and myelencephalon, give rise to ______ nerves. Name the rhombomeres that give rise to each CN and if they are associated with a phar arch, which one.
cranial motor nerves. cn IV: from R1 CN V: from R1, 2, 3 to P1 CN VII: from R4&5 to P2 CN VI: from R5 CN IX: from R6 to P3 CN X: from R7 to P4 CN XI & XII: from R8
In embryonic neurogenesis, neurons are derived directly from
early radial glial cells, not neuronal intermediate progenitor cells
The subplate neurons's role:
establishing connections between cortex and developing thalamus. form transient synaptic connections.
Holoprosencephaly
eyes fuse to form one central eye (cyclops) because lateral ventricles fuse. MIlder form: just incomplete devo of midline structures
At the end of week _____, the motor nerve fibers of ventral basal plate arise, and eventually join with the _______ of the dorsal alar plate to make ______.
four; Dorsal nerve root post ganglion; spinal nerves!
Chiari malformation
herniation of cerebellum, tonsils, and medulla down formen magnum.
encephalocoele:
herniation of intracranial contents via defect in cranium
The thalami are the
hypothalamus, thalamus, and epithalamus.
Special visceral efferents:
innervate skeletal BRANCHIOMERIC muscles: muscles related to pharyngeal arches.
Hippocampus: neurons can also develop from here, but they come from ____
intermediate precursors from subgranular zone's radial glia.
Ependymal cells come from
late formed radial glial cells
Oligodendrocytes arise from _____
lateral radial glia, and they form oligodendrocyte intermediate precursors
Diencephalon (thalami): Thalami first appear as bulge on..
lateral walls of third ventricle
The ___ zone is formed first, above the ______ zone
marginal, ventricular
The aqueduct of Sylvius comes from the neural canal of the _____ and it connects the _______ to the ______
mesencephalon, fourth to third ventricle.
Spina bifida cystica: meningomyelocele
more severe form of SBC, spinal cord and nerve roots AND meningeal sac protrudes through defect (to right)
General somatic efferent fibers (motor) refer to
motor nerves for skeletal muscle,
Neurons of ventral side of spinal cord (basal) send out ___ nerves to innervate ____
motor nerves to innervate muscles!
The first thing made by the ventricular layer in the developing spinal cord is _______ that migrate to the mantle layer
neuroblast cells.
The anterior commissure forms first and connects...
olfactory bulbs and center of hemispheres.
Neural crest cells become tons of things, including...
parasympathetic ganglia of CN's, pharyngeal arches, glial cells, peripheral sensory neurons, parasympathetic and sympathetic peripheral motor neurons, dorsal root ganglia for sensory relay.
Another part of diencephalon!: Pituitary gland: duel developmental origins: origin of posterior lobe (neurohypophysis)
posterior lobe of pituitary: distal part of infundibulum (diverticulum in floor of third ventricle) (grows ventrally towards stomodeum)
General visceral efferent fibers (motor) refer to
preganglionic autonomic fibers (innervation of glands and such)
Neuroblasts from basal plates migrate ventrally to become many things, including:
red nuclei, reticular nuclei, motor nuclei or CN III and CN IV.
The POST commissures form next and connect
right and left hippocampus
Alar plate contains cell bodies (nuclei) of the
sensory neurons (general somatic, general visceral, and general special visceral AFFERENTS) DAS
Special somatic afferents:
sight, hearing, equilibrium
Because the medulla body becomes flat, four columns of sensory nuclei are developed dorsal to sulcus limitans:
special somatic, general somatic, Special visceral, General visceral. ALL afferents ( sensory)
The layer that goes away (is transient) in cortical development is the
subplate.
Reelin
the molecular signal telling cells to stop migrating up once they get past the layer they're supposed to be on top of.
The Diencephalon's neural canal becomes the
third ventricle
Neurogenesis of cerebellum occurs in _____ distinct proliferative zones, and each zone gives rise to a different cell population in the cerebellum.
two
LIM1 expressed in prechordal plate and neural plate , designates --> OTX2 expression there too, designates -->
Forebrain Midbrain
3 primary vesicles of the brain at day 26 (week four)
Forebrain: prosencephalon Midbrain: mesencephalon Hindbrain: rhombencephalon
Cervical flexure:
Forms between rhombencephalon and spinal cord, does not persist in adult
The rhombencephalon's neural canal becomes the
Fourth ventricle.
Encephalocoele: meningohydroencephalocele:
Meninges, part of brain and part of ventricular system outside of cranium. Born with big bulge growing outside of head.
What is the defect that is a severe form of rostral neuropore defect, in which parts of cranium do not form (usually forebrain, midbrain, and hindbrain)?
Meroencephaly (baby Jaxon)
The rhombencephalon, during week 5, divides into the :
Metencephalon and myelencephalon
The mesencephalon's adult derivative is the
Midbrain
Spina bifida cystica: Raschischisis/myeloschisis
Most severe form of any spina bifida. Neural tube failed to fuse, so you have flat neural mass directly exposed to amniotic fluid --> necrosis
Basal plate is a nucleus forming ventral gray matter, and it sends input by way of ________ to _________ and also forms _________.
Motor fibers to skeletal muscle; and also forms ventral roots of spinal nerves. (bottom pink)
The basal plate contains cell bodies (nuclei) of the
Motor neurons (general somatic, general visceral, and special visceral EFFERENTS) BDM
The mesencephalon, during week 5, divides into the :
NOPE! doesn't divide. stays as is.
General visceral sensory fibers (afferent) refer to
Nerve fibers sensing information from internal organs (viscera)
General somatic sensory fibers (afferent) refer to
Nerve fibers sensing pain, temperature, and touch in skin, muscles and joints
Two things that can become mesenchyme:
Neural crest cells and mesoderm. ?? check
Cranial nerve sensory GANGLIA are derived from _________ (4)
Neural crest cells, like the dorsal root ganglia; Ectodermal placodes; Epibranchial placodes; diffuse trigeminal placode.
To form neural cells, the ventricular layer first forms _______ which migrate to form the mantle layer
Neuroblasts
The layer surrounding the central canal is called the _______ and it has precursor cells to give rise to _______. It is called the ______ zone.
Neuroepithelial (ependymal) layer; neurons and macroglia; Ventricular zone *Proliferation from inside out!
The neuroepithelium of the ventricular layer can also form apolar neuroblasts, which eventually extend processes to form an axon and dendrite, and become ________.
Neurons.
Anencephaly
No cranial neuropore closure. skull doesn't form and deformed nervous system exposed to amniotic, fluid = necrosis
Neural tube formation: quick review
Notochord and primitive node induces formation of neural tube. Neural tube begins as invagination of neural folds. Rostral neuropore closes by day 25-26, Caudal neuropore closes by day 27-28. lumen of neural tube --> neural canal. **but up to 5 diff sites of neural tube closure --> diff neural tube defects. Secondary neurulation: complete by week 8.
Most parasympathetic ganglia are derived from neural crest cells at the ________ or ______ regions.
Occipito-cervical (like vagus/CN X) or sacral regions (pelvic nerve).
Myelination: done by ____ in CNS and ____ in PNS.
Oligodendrocytes in CNS, and Schwann cells in PNS. myelination happens slowly, from 20 weeks to after birth.
Alar neurons usually stay dorsal, and basal neurons usually stay ventral, but one special nucleus travels from dorsal to ventral side, and it is important for hearing. It is called the ______.
Olivary nucleus. Exception to sensory neuron migrating ventrally.
Neurogenesis of cerebellum: the external germinal layer undergoes three waves of proliferation and produce...
Basket cell neuroblasts, granule cell neuroblasts, stellate neuroblasts AND GLIOBLASTS (--> macroglia, astrocytes and oligodendrocytes)
Another part of diencephalon!: Pineal gland forms as an outpocketing of the _________.
Caudal diencephalon. Pineal: melantonin, circadium rhythms.
The telencephalon's adult derivative is the
Cerebral hemispheres
The three flexures (curves/dips) in the C-shaped embryo starting in week 5:
Cervical Cephalic (mesencephalic, midbrain) Pontine (dorsal)
Ependymal cell lining is made by...
Glioblast differentiation from neuroepithelia of neural canal, then glioblasts become macroglia (astrocytes and oligodendrocytes) --> ependymal layer/ventricular zone.
medulla devo: neuroblasts migrate dorsolaterally from the alar plate and form little islands of cell bodies called_______.
Gracile and cuneate somatosensory relay nuclei of the spinal cord.
AP axis of forebrain, midbrain, and hindbrain is controlled by
HOX (but Hox class of hindbrain is diff from HOX class of fore and midbrain)
____ genes affect the development of the forebrain and midbrain.
HOX! also, like hindbrain.
Defects in closure of rostral neuropore leads to :
Incomplete devo of brain, calvaria, or face.
At week 8, the spinal cord of baby ends at level: In adults, the spinal cord ends at level:
L4- L5 L1-L2
The telencephalon's neural canal becomes the
Lateral ventricles
Cerebral hemispheres form as outgrowths of______, and they are in communication with ____ at first.
Lateral walls of prosencephalon! In a C shape. Lateral ventricles!
The basal plate of the mesencephalon gives rise to the
MOTOR nuclei (red nucleus, reticular nuclei, CN III and IV's motor nuclei)
Processes extend from the mantle layer to form another layer called the ________
Marginal zone, which becomes white matter (no cell bodies here)
The layers of the cortex, from outside in, at first, are
Marginal, cortical, subplate, intermediate, (ventricular)
Inside out devo of cortex:
Marginal, cortical, then subplate develop.. then layers start growing inside out between subplate and cortical layers.
The myelencephalon's adult derivative is the
Medulla