Nervous System Development Flashcards
The neural plate is a ________ that appears in the ____ week in the _____
The neural plate is a thickened specialized epithelium that appears in the 3rd week in the ectoderm
In the neural plate, the region as far caudal as the fourth pair of somites will form the ______ and the rest will make the ________
In the neural plate, the region as far caudal as the fourth pair of somites will form the brain and the rest will make the spinal cord
Fusion of the neural plate occurs in the ___ week starting in the ____ region
Fusion of the neural plate occurs in the 4th week starting in the occipital region
What is required when the neural tube becomes fully closed inside the body? What is overtop?
Neural tissue is below a surface ectoderm and is segregated from the amniotic fluid = requires a vascular supply
The neural plate forms the central forms the _______
The neural plate forms the central forms the Central Nervous system
(Region as caudal as 4th somite forms brain and the rest makes the spinal cord)
The entire peripheral nervous system is derived from ______
The entire peripheral nervous system is derived from Neural Crest
What are the four basic steps in the creation of a nervous system?
- Regionalization
- divide neural tube into brain and spinal cord, and then further subdivision
- Cell proliferation and differentiation
- produce variety of neurons, glia and other cells that make up a functioning nervous system
- Organization
- Most neurons must migrate from where they are born to where they function
- Connectivity
- neurons extend axons and dendrites and make synapses with one another and with target tissues
What is segmentation of the neural tube? What structures are produced from this segmentation?
- Week 3:
- before the neural plate begins to fold indentations appear that make the 3 primary brain vesicles
- Prosencephalon (forebrain)
- Mesencephalon (midbrain)
- Rhombencephalon (hindbrain)
- before the neural plate begins to fold indentations appear that make the 3 primary brain vesicles
What are the three primary brain vesicles and what do they ultimately become?
- Prosencephalon (forebrain)
- Mesencephalon (midbrain)
- Rhombencephalon (hindbrain)
What are the secondary brain vesicles? When do they develop?
Week 5:
- Prosencephalon divides into
- Telencephalon (cerebral hemispheres)
- Diencephalon (interbrain)
- Rhombencephalon divides into:
- Metencephalon (pons and cerebellum)
- Myelencephalon (medulla)
- Mesencephalon stays as mesencephalon and makes hindbrain
The central lumen in each of the secondary brain vesicles take on a unique morphology, creating the _____
The central lumen in each of the secondary brain vesicles take on a unique morphology, creating the ventricular system (spaces for CSF)
Secondary Brain Vesicles LABEL THE IMAGE SLIDE 6
LABEL THE IMAGE SLIDE 6
What are the 2 brain flexures? Where are they located?
-
Mesencephalic flexure
- at the midbrain-hindbrain boundary
-
Pontine flexure
- at the metencephalon/myelencephalon boundary (between the two divisions of the hindbrain/rhombencephalon)
The midbrain-hindbrain boundary function:
The midbrain-hindbrain boundary (MHB) functions as an organizing centre for mid/hindbrain development
The ventral bend at the midbrain/hindbrain boundary is called the:
Mesencephalic flexure
The posterior bend at the metencephalon/myelencephalon boundary is the _____
What happens at this region?
The posterior bend at the metencephalon/myelencephalon boundary is the Pontine flexure
What happens at this region?
- opening of the 4th ventricle into rhomboid shape - region becomes compressed
The _______ dictate orientation of the brain
The flexures dictate orientation of the brain
________ overgrows diencephalon and midbrain. _____ overgrows much of the hindbrain
telenchephalon overgrows diencephalon and midbrain. cerebellum overgrows much of the hindbrain
What region of the brain makes gyri and sulci?
Telencephalon
The early neural tube is ________
These cells are anchored at both the ___ and ____ surface
SLIDE 9
The early neural tube is pseudostratified neuroepithelium (stem cells for CNS)
These cells are anchored at both the apical (lumen of neural tube - became inner surface lining the lumen upon folding) and basal (outside of neural tube - was bottom before folding) surface
What is interkinetic nuclear migration?
- Controlled mitotic division
- nuclei move up and down coordinated with cell cycle
- The nuclei move back and forth along the apical-basal axis in sync with their cell cycle
- DNA replication (S phase) occurs while the nucleus is displaced from the apical surface
- Cell division always occurs at the apical surface
Interkinetic nuclear migration
- Controlled mitotic division
- The nuclei move back and forth along the ______ in sync with their_____
- DNA replication (S phase) occurs while________
- Cell division always occurs at the _______
Interkinetic nuclear migration
- Controlled mitotic division
- The nuclei move back and forth along the apical-basal axis in sync with their cell cycle
- DNA replication (S phase) occurs while the nucleus is displaced from the apical surface
- Cell division always occurs at the apical surface
Neuroepithelial cells can divide ______ or _____
Symmetric divisions occur early to ______ or late to ___
Most divisions are _____
- Neuroepithelial cells can divide asymmetrically or symmetrically
- asymmetric: give rise to two different cell types
- Symmetric: two of the same cell type
- Symmetric divisions occur early to build the stem cell population or late as terminal divisions
- Most divisions are asymmetric: the stem cell self-renews and makes one progenitor (neuroblast/glioblast) or one postmitotic cell (neuron, glia)
How do neuroepithelial cells give rise to neurons, glia and ependymal cells (spatially or temporally (sequentially))
Neuroepithelial cells give rise sequentially to neurons, glia, and ependymal cells (line ventricles and make CSF)
Most neuroepithelial cells terminally differentiate as _____ or _____
SLIDE 12
Most neuroepithelial cells terminally differentiate as ependymal cells or astrocytes (glia)
________ line the ventricle and make cerebrospinal fluid (CSF)
Some neuroepithelial cells remain in _______ as ______
SLIDE 13
ependymal cells line the ventricle and make cerebrospinal fluid (CSF)
Some neuroepithelial cells remain in specific regions of the CNS as stem cells (don’t maintain neuroepithelial identity)
LAYERING IN CNS
- As neurons are made, what happens to the neural tube?
As neurons are made, the neural tube becomes segregated into a proliferative layer, a layer(s) of postmitotic cells, and a layer of axon tracts
As neurons are made, the neural tube becomes segregated into a proliferative layer, a layer(s) of postmitotic cells, and a layer of axon tracts
- the neuronal layers are the _____ and the axon tracts form the ______
Slide 14
As neurons are made, the neural tube becomes segregated into a proliferative layer, a layer(s) of postmitotic cells, and a layer of axon tracts
- the neuronal layers are the gray matter and the axon tracts form the white matter
What are the 4 types of neurons?
- Somatic motor neurons
- innervate voluntary muscles
- Visceral motor neurons
- autonomic nervous system (sympathetic and parasympathetic neurons)
- Control visceral function (eg heartrate, digestion, salivation)
- Sensory Neurons
- Receive touch, pain, temperature, proprioceptive information
- mediate special senses
- Association neurons (interneurons)
- Connect neurons to one another.
- process information
- planning
- thinking
- Somatic motor neurons
- innervate ______
- Visceral motor neurons
- _________
- Control _______
- Sensory Neurons
- Receive ________ information
- mediate ______
- Association neurons (interneurons)
- ________.
- process _____
- _____
- ______
- _____
- Somatic motor neurons
- innervate voluntary muscles
- Visceral motor neurons
- autonomic nervous system (sympathetic and parasympathetic neurons)
- Control visceral function (eg heartrate, digestion, salivation)
- Sensory Neurons
- Receive touch, pain, temperature, proprioceptive information
- mediate special senses
- Association neurons (interneurons)
- Connect neurons to one another.
- process information
- planning
- thinking
Somatic motor neurons and preganglionic visceral motor neurons originate in the ____
Sensory neurons and post-ganglionic visceral motor neurons develop from ______
Somatic motor neurons and preganglionic visceral motor neurons originate in the cns
Sensory neurons and post-ganglionic visceral motor neurons develop from neural crest
_________ and _________ originate in the cns
_______ and __________ develop from neural crest
Somatic motor neurons and preganglionic visceral motor neurons originate in the cns
Sensory neurons and post-ganglionic visceral motor neurons develop from neural crest
Define:
- Nucleus
- Ganglion
- Tract
- Nerve
Define:
- Nucleus
- collection of neuronal cell bodies in the CNS
- Ganglion
- collection of neuronal cell bodies in the PNS
- Tract
- bundle of axons in the CNS
- Nerve
- bundle of axons in the PNS
What happens in the spinal cord to allow production of different types of neurons?
Need to pattern the spinal cord in order to produce different types of neurons
LABEL THE SPINAL CORD
label the spinal cord
DORSAL-VENTRAL PATTERNING OF THE SPINAL CORD
- _____ is expressed in the notochord, underlying the midline of the neural plate
- _____ are originally excluded from the neural plate, but are expressed in the surrounding ectoderm
- Shh is expressed in the notochord, underlying the midline of the neural plate
- BMPs are originally excluded from the neural plate, but are expressed in the surrounding ectoderm
- Shh is expressed in the ______\_, underlying the midline of the _______
- BMPs are originally excluded from the ______\_, but are expressed in the surrounding ______\_
- Shh is expressed in the notochord, underlying the midline of the neural plate
- BMPs are originally excluded from the neural plate, but are expressed in the surrounding ectoderm
SLIDE 21: DORSAL-VENTRAL PATTERNING OF THE SPINAL CORD
- As plate folds into a tube, a ____ is formed that expresses ____
- ____ in the notochord induces the formation of the ____ in the ventral neural tube. The floor plate also begins to express Shh
- The floor plate and roof plate are_________
- As plate folds into a tube, a roof plate is formed that expresses BMPs
- Shh in the notochord induces the formation of the floor plate in the ventral neural tube. The floor plate as begins to express Shh
- The floor plate and roof plate are non-neurogenic signaling centres
SLIDE 22 DORSAL-VENTRAL PATTERNING OF THE SPINAL CORD
- BMPs expressed by the _____ pattern the ____ neural tube
- Shh expressed by the _____ patterns the _____ neural tube
- BMPs expressed by the roof plate pattern the dorsal neural tube
- Shh expressed by the floor plate patterns the ventral neural tube
SLIDE 22 DORSAL-VENTRAL PATTERNING OF THE SPINAL CORD
- Neurons in the ventral neural tube form the _____
- Neurons in the dorsal neural tube form the _____
- Neurons in the ventral neural tube form the basal plate
- Neurons in the dorsal neural tube form the alar plate
SLIDE 22
The basal plate, formed by neurons in the _____ will make the ______ neurons
The basal plate, formed by neurons in the basal plate will make the motor neurons
SLIDE 22
The alar plate, formed from neurons in the ______, makes the ______
The alar plate, formed from neurons in the dorsal neural tube, makes the association neurons (sensory)
_______ make peripheral neurons
neural crest makes peripheral neurons
- Neural crest cells delaminate from the edges of the folding neural plate and migrate into sclerotomes (dorsal side) MET → migrate into surrounding tissue
neural crest makes peripheral neurons, how?
neural crest makes peripheral neurons
- Neural crest cells delaminate from the edges of the folding neural plate and migrate into sclerotomes (dorsal side) MET → migrate into surrounding tissue
- Some neural crest cells stay close to the neural tube. These cells will give rise to clusters of sensory neurons called the dorsal root ganglia
- Some NC cells migrate further and come to lie next to the aorta.
- These form the sympathetic ganglia
- Parasympathetic ganglia are near or within organs, and so neural crest cells migrate to those sites
SLIDE 24 PERIPHERAL NERVOUS SYSTEM:
neural crest makes peripheral neurons
- Neural crest cells delaminate from the edges of the _______ and migrate into _______(dorsal side)
- Some neural crest cells stay close to the neural tube. These cells will give rise to clusters of ______ called the ________
- Some NC cells migrate further and come to lie next to the aorta.
- These form the _______
- _________ are near or within organs, and so neural crest cells migrate to those sites
neural crest makes peripheral neurons
- Neural crest cells delaminate from the edges of the folding neural plate and migrate into sclerotomes (dorsal side) MET → migrate into surrounding tissue
- Some neural crest cells stay close to the neural tube. These cells will give rise to clusters of sensory neurons called the dorsal root ganglia
- Some NC cells migrate further and come to lie next to the aorta.
- These form the sympathetic ganglia
- Parasympathetic ganglia are near or within organs, and so neural crest cells migrate to those sites
SLIDE 25 SPINAL NERVES: SOMATIC MOTOR
- ______ are the first neurons to extend axons out of the spinal cord
SLIDE 25 SPINAL NERVES: SOMATIC MOTOR
- motor neurons are the first neurons to extend axons out of the spinal cord
Label the image Spinal Nerves
slide 25
The _______ determines the segmental pattern of the spinal nerves
The sclerotome determines the segmental pattern of the spinal nerves
Autonomic Motor Spinal Nerves
- Autonomic neurons develop in the _______ of the spinal cord
- Their axons exit through the ______ with the _____
- Autonomic neurons develop in the intermediolateral gray matter of the spinal cord
- Their axons exit through the ventral root with the motor axons
Sympathetic neurons form at levels ______
Parasympathetic neurons form at level ____
Sympathetic neurons form at levels T1-L2
Parasympathetic neurons form at sacral region
What is unique about the axons of Dorsal root ganglia neurons?
- Dorsal root ganglia neurons form 2 axon-like processes: one peripheral axon that grows out to skin and organs, and a central axon that carries the sensory information into the spinal cord
The autonomic nervous system is a _____ system with a ____ forming in the CNS and a _____ forms from neural crest and sitting in a ganglion outside the CNS
The autonomic nervous system is a 2-neuron system with a preganglionic neuron forming in the CNS and a postganglionic forms from neural crest and sitting in a ganglion outside the CNS
The autonomic nervous system is a 2-neuron system with a preganglionic neuron forming in the _____ and a postganglionic neuron which forms from _______ and sits in a ______ outside the CNS
The autonomic nervous system is a 2-neuron system with a preganglionic neuron forming in the CNS and a postganglionic neuron which forms from neural crest and sits in a ganglion outside the CNS
The sympathetic ganglia form adjacent to the ______ and _____
They have ______ connections between them and so are called the ________
The sympathetic ganglia form adjacent to the vertebrae and aorta
They have axonal connections between them and so are called the sympathetic chain ganglia
Label:
What are growth cones?
A growth cone is a sensory apparatus found at the tip of a growing axon
It senses the environment and directs the axon to its target
- Sensors that test environment
- Find signals and follow cues they find attractive and turn away from deterent cues
Axon guidance molecules can be: (4)
- Inhibitory or attractive
- Secreted or membrane bound
In vivo, axon growth is restricted by _____ in the developing embryo
Rather than continuously searching for the correct route, axons encounter specific choice points
What happens here?
In vivo, axon growth is restricted by _____ in the developing embryo
Rather than continuously searching for the correct route, axons encounter specific choice points
- The growth cone enlarges, samples the environment for cues and makes a guidance decision
Axons that cross the midline are called:
Axons that cross the midline are called: Commissural axons
In the spinal cord, commissural axons are first repelled _____ by ______
In the spinal cord, commissural axons are first repelled ventrally by BMPs
What induces axons to grow ventrally in the spinal cord (ie to cross the midline)
Neuroepithelial cells secret netrin at their pial surface
Axons (with netrin receptor) follow a netrin highway to the floor plate
Floor plate as a choice point:
- Some axons travel ventrally but _______
- The floor plate secretes another guidance cue: ____
Floor plate as a choice point:
- Some axons travel ventrally but remain ipsilateral and do not enter the floor plate
- The floor plate secretes another guidance cue: Slit
- axons expressing the slit receptor, Robo, are prevented from crossing the midline
Floor plate as a choice point:
- Some axons travel ventrally but remain ipsilateral and do not enter the floor plate
- The floor plate secretes another guidance cue: Slit
- Role of Slit?
Floor plate as a choice point:
- Some axons travel ventrally but remain ipsilateral and do not enter the floor plate
- The floor plate secretes another guidance cue: Slit
- axons expressing the slit receptor, Robo, are prevented from crossing the midline
The dorsal root ganglion neurons undergo massive apoptosis, except in the regions of the ______. Target tissues secrete _____ (e.g., nerve growth factor), and there is more target tissue in the ____ than along the _____
The DRG neurons undergo massive apoptosis, except in the regions of the limb buds. Target tissues secrete survival factors (e.g., nerve growth factor), and there is more target tissue in the limbs than along the trunk
Motor neuron apoptosis and pruning:
- Motor neurons undergo apoptosis but the connections are also pruned
- How does this change the connections between motor neurons and muscle fibers?
Motor neuron apoptosis and pruning:
- Motor neurons undergo apoptosis but the connections are also pruned
- Initially, each muscle fibre receives input from multiple motor neurons, but synapses are pruned so only one motor neuron innervates a muscle fibre
The end of the spinal cord is called the ______ and the bundle of spinal roots extending caudally is the _____
The end of the spinal cord is called the conus medullaris and the bundle of spinal roots extending caudally is the cauda equina
What anchors the spinal cord at the first coccygeal vertebra?
A fibrous piece of pia mater called the terminal filum extends caudally to anchor the SC at the first coccygeal vertebra
Label:
Label:
What are rhombomeres?
Rhombomeres are a series of 7 swellings that form in the hindbrain
- They are compartments, in that there are discrete boundaries between them and very little cell mixing occurs
They form in the 4th week and disappear in the 6th
How many cranial nerves are associated with the hindbrain?
8 of 12 cranial nerves are associated with the hindbrain
Most cranial motor nerves arise in ______
Most cranial motor nerves arise in rhombomeres
- The segmentation of the rhombencephalon sets up the organization of the cranial motor nerves
- The segmentation of the rhombencephalon sets up the organization of the ________
- The segmentation of the rhombencephalon sets up the organization of the cranial motor nerves
Ectodermal/neurogenic placodes are very similar to _____ but cells don’t ______
Instead they:
Ectodermal/neurogenic placodes are very similar to neural crest but cells don’t undergo EMT and disperse immediately
Instead they: aggregate into clumps of thickened ectoderm (endothelium), creating the primordia (neural tissue/neural associated tissue eg lens) of different tissues
Both ______ and ______ contribute to cranial nerve sensory and autonomic ganglia
Both neural crest and neurogenic/ectodermal placodes contribute to cranial nerve sensory and autonomic ganglia
The hindbrain “opens” into a ______ shape
- opened space but still “closed” — stretching of ______
In the 5th week, the ______ side of the fourth ventricle splays open, giving the hindbrain a diamond shape and forming the ______
The hindbrain “opens” into a rhomboid shape.
opened space but still “closed” — stretching of roof plate
In the 5th week, the dorsal side of the fourth ventricle splays open, giving the hindbrain a diamond shape and forming the 4th ventricle
The region of the brain that controls basic functions and resembles the spinal cord in organization:
The brainstem
_____/_____ are displaced laterally upon formation of the 4th ventricle
alar plates/dorsal columns are displaced laterally upon formation of the 4th ventricle
Where the roof plate meets neural tissue is the _______
Where the roof plate meets neural tissue is the rhombic lip (upper/lower)
The Rhombic lip makes _____
Cerebellum
The lumen of the midbrain (mesencephalon) will shrink to form the ______, connecting the ____ and __ ventricles
The lumen of the midbrain (mesencephalon) will shrink to form the cerebral aqueduct, connecting the 3rd and 4th_ ventricles
The midbrain exhibits very little ____ but does house _____
The midbrain exhibits very little growth and is only a small part of the final brain but does house some important nuclei
Most neurons migrate from where they are born to their final position. This migration can be ____ or ____ relative to the neural tube
Most neurons migrate from where they are born to their final position. This migration can be radial or tangential relative to the neural tube
- Radial = perpendicular to the ventricular zone (central canal)
- Tangential is parallel to the ventricular zone
What are the four layers of the cerebellum?
- Molecular Layer
- Mostly dendrites of purkinje cells
- Purkinje layer
- where cell bodies are
- integrating centre
- Granule Cell layer
- tiny cells
- make up >50% cells in the brain
- Provide input to the purkinje cells
- White Matter
- Axon tracts coming/going
The four layers of the cerebellum:
- Molecular Layer
- Mostly _______of ______cells
- Purkinje layer
- where ______ are
- ______centre
- Granule Cell layer
- _______
- make up____cells in the brain
- Provide input to the ______
- White Matter
- ________
- Molecular Layer
- Mostly dendrites of purkinje cells
- Purkinje layer
- where cell bodies are
- integrating centre
- Granule Cell layer
- tiny cells
- make up >50% cells in the brain
- Provide input to the purkinje cells
- White Matter
- Axon tracts coming/going
The hindbrain has 2 distinct proliferative zones: the _____ and ______
The hindbrain has 2 distinct proliferative zones: the ventricular zone and rhombic lip
What is the Rhombic lip?
- Rhombic lip is a thin strip along the dorsal-medial edge of the alar plate.
- R1 has the upper Rhombic Lip (URL)
- R2-R8 = Lower rhombic lip (LRL)
The Upper Rhombic Lip (URL) gives rise to ______ that migrate over the surface of the ________
SLIDE 23B
The Upper Rhombic Lip (URL) gives rise to progenitor cells that migrate over the surface of the rhombomere 1 (still dividing as they migrate)
Slide 23B
The progenitor cells from the upper rhombic lip create a _______ which produces cerebellar granule neurons
Slide 23B
The progenitor cells from the upper rhombic lip create a new germinal zone, the external granule cell layer (EGL) which produces cerebellar granule neurons (make up >50% of brain neurons)
The progenitor cells from the upper rhombic lip create a new germinal zone, the external granule cell layer (EGL) which produces ________
The progenitor cells from the upper rhombic lip create a new germinal zone, the external granule cell layer (EGL) which produces cerebellar granule neurons (which make up >50% of brain neurons)
Granule cells are born in the _____ and then migrate internally through the ________ to form the ________
Granule cells are born in the EGL (external granule cell layer) and then migrate internally through the purkinje cells to form the inner granule cell layer
Slide 25B
Granule cells are born in the EGL (external granule cell layer) and then migrate internally through the purkinje cells to form the inner granule cell layer
AT THE SAME TIME: what is happening with the purkinje cells?
Purkinje cells are migrating radially (externally) away from the ventricular zone where they were born
How is the connection between granule cells and purkinje cells established?
As GCs migrate internally (through the purkinje cells) they reel out an axon behind them (2 axons on either side like a T).
The axon will form synapses with Purkinje cell dendrites
Slide 26B GRANULE CELL MIGRATION
Granule cells:
- Proliferate in the ______ and then become _____
- Adopt a _____ morphology and extend _____ within the plane of the _______
- Attach to ______
- Cell body migrates through _______ to ______ by travelling along ______
- Leave behind a _______
Granule cells:
- Proliferate in the EGL and then become post-mitotic
- Adopt a bipolar morphology and extend 2 axons within the plane of the EGL
- Attach to Bergmann glia
- Cell body migrates through purkinje cell layer to inner granule cell layer by travelling along glial fibres
- Leave behind a bifurcated axon (parallel fibre) == T-shaped axon
Label the layers of the cerebellar cortex
What is contained in each layer?
The Cerebellar Cortex has three layers:
- Molecular Layer
- purkinje cell dendrites & granule cell axons
- Purkinje cell layer
- purkinje cells
- Granule cell layer
- Granule cells & purkinje cell axons
The Cerebellar Cortex has three layers; what is contained in each layer?
- Molecular Layer
- __________
- Purkinje cell layer
- ________
- Granule cell layer
- _______
The Cerebellar Cortex has three layers:
- Molecular Layer
- purkinje cell dendrites & granule cell axons
- Purkinje cell layer
- purkinje cells
- Granule cell layer
- Granule cells & purkinje cell axons
The cerebellum develops extensive _____ and is divided into ____ with specific functions
The cerebellum develops extensive foliation and is divided into lobes with specific functions
What forms the cerebellar hemispheres? Where are the hemispheres connected?
- The two sides of dorsal rhombomere 1 grow to form the cerebellar hemispheres
- Connected by the VERMIS
Initially, the cerebellum is ______ to the 4th ventricle. It expands, however, to overgrow the _____, _____ and ______
Initially, the cerebellum is cranial to the 4th ventricle. It expands, however, to overgrow the pons, most of the medulla and the 4th ventricle (moves backwards and over the ventricle as it expanded)
What is cerebellar hypoplasia?
Failure of the cerebellum to develop properly.
Often not an isolated incident
Rest of brain will compensate
Cerebellum controls fine motor skills, coordination and balance
Telencephalon overgrows _______
Slide 32B
Telencephalon overgrows diencephalon
- telencephalon = cerebral hemispheres
FOREBRAIN
- the diencephalon forms the ______ and _____
- The telencephalon forms the ______ ventrally and ______ and _______ dorsally
SLIDE 33B
FOREBRAIN
- the diencephalon forms the thalamus and hypothalamus
- The telencephalon forms the basal ganglia ventrally and cerebral cortex and hippocampus dorsally
The Cerebral cortex has ____ layers based on _____ and _______
SLIDE 34B
The Cerebral cortex has 6 layers based on anatomy and function
- Cells in each layer receive specific inputs and have specific functions
What type of neuronal development/patterning occurs in the cerebral cortex (temporal or spatial)
- Temporal Patterning - waves w/ dif identities
Slide 35B
- the neuroepithelium of the cortex is initially the same as elsewhere. It will generate neurons in _____
- The first born neurons form a layer called the _______
- they send their axons ______ instead of _____ forming the white matter tracts of the ________
Slide 35B
- the neuroepithelium of the cortex is initially the same as elsewhere. It will generate neurons in waves
- The first born neurons form a layer called the preplate
- they send their axons apically instead of basally forming the white matter tracts of the intermediate zone (IZ)
SLIDE 36B - CORTICAL MIGRATION
- Most neuroepithelial cells differentiate into _______ which span the width of the cortex and along which neurons migrate to reach the upper layers
- The next wave of neurons generated forms the ______ and splits the preplate into the _____ and _______
- The ventricular zone gives rise to the _________ (2nd proliferative zone)
- Most neuroepithelial cells differentiate into radial glial cells which span the width of the cortex and along which neurons migrate to reach the upper layers
- The next wave of neurons generated forms the cortical plate and splits the preplate into the marginal zone (MZ) and subplate (SP)
- The ventricular zone gives rise to the subventricular zone (2nd proliferative zone)
What is the subventricular zone?
- Second proliferative zone basal to VZ that contains neuroblasts and gliablasts
Slide 37B
What is meant by “inside out manner” by which the cortex is made?
What is the exception?
The cortex generates neurons in waves and each new wave migrates past the previous one = inside out; Dependent on Radial Glia (Bottom up generation)
The marginal zone (MZ) is the exception: it becomes Layer 1 followed by layer 6, 5, 4, 3, and 2
37B
Label the layers of the cortex
Label the layers of the cortex
Slide 38B
What is Reelin? Where is it secreted from?
- Reelin is a morphogen necessary for radial migration of cortical neurons.
- Without Reelin the inside-out pattern is lost and new waves of neurons pile-up inside the layers containing previous born neurons
- Reelin is secreted from the Cajal-Retzius cells of the marginal zone
SLIDE 39B
What does the final cortex look like?
- Will have _____ layers of neurons
- The _____ degenerates (doesn’t contribute to the layers)
- _______ cells die
What does the final cortex look like?
- Will have up to 6 layers of neurons
- The subplate degenerates (doesn’t contribute to the layers)
- Most Cajal-Retzius cells die once migration is finished = layer 1 is small
Slide 40B
- Where are inhibitory neurons born and how do they get to the cerebral hemisphere?
- What about the remaining neurons?
- The ventral (non-cortex) part of the telencephalon is the ganglionic eminence (GE)
- Some GE neurons migrate tangentially into the cortex and differentiate as the inhibitory neurons of the cortex (mostly GABAergic)
- Remaining GE neurons form basal ganglia
41B
How do sulci and gyri form in the cortex?
As new neurons are generated in the cortex, the cerebral walls expand and then fold to form the sulci and gyri
- Folding is not just dependent on neurons but from cortical migration
What is lissencephaly?
- Smooth brain
- disruption in gyrification
- Usually caused by improper cell migration in the cortex and can be the result of genetic disorders or viral infections
- Wide spectrum of lissencephalies - may result in severe cognitive deficits, seizures and even perinatal death
The brain is only about _____ of its adult volume at birth
- Further growth is partly from _____ but mostly from _____
- Brain reaches its final size at about ______
The brain is only about 25% of its adult volume at birth
- Further growth is partly from extension of neuronal processes but mostly from myelination
- Brain reaches its final size at about 7 years
Neural stem cells (ie ________ cells)
- Some cells derived from radial glia lose their connections to the pial and ventricular surface but maintain _______ markers
- They remain in the _______ lining the anterior portions of the _______ and are capable of proliferating in the adult
- Newly born neurons migrate into the ______ and differentiate as _______
- There are also neural stem cells in the _______
Neural stem cells (ie neuroepithelial cells)
- Some cells derived from radial glia lose their connections to the pial and ventricular surface but maintain RGC markers (RGC=radial glial cell)
- They remain in the subventricular zone (SVZ) lining the anterior portions of the lateral ventricles and are capable of proliferating in the adult
- Newly born neurons migrate into the olfactory bulbs and differentiate as interneurons
- There are also neural stem cells in the hippocampus
