Nervous System Development Flashcards
1
Q
The neural plate is a ________ that appears in the ____ week in the _____
A
The neural plate is a thickened specialized epithelium that appears in the 3rd week in the ectoderm
2
Q
In the neural plate, the region as far caudal as the fourth pair of somites will form the ______ and the rest will make the ________
A
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
3
Q
Fusion of the neural plate occurs in the ___ week starting in the ____ region
A
Fusion of the neural plate occurs in the 4th week starting in the occipital region
4
Q
What is required when the neural tube becomes fully closed inside the body? What is overtop?
A
Neural tissue is below a surface ectoderm and is segregated from the amniotic fluid = requires a vascular supply
5
Q
The neural plate forms the central forms the _______
A
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)
6
Q
The entire peripheral nervous system is derived from ______
A
The entire peripheral nervous system is derived from Neural Crest
7
Q
What are the four basic steps in the creation of a nervous system?
A
- 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
8
Q
What is segmentation of the neural tube? What structures are produced from this segmentation?
A
- 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
9
Q
What are the three primary brain vesicles and what do they ultimately become?
A
- Prosencephalon (forebrain)
- Mesencephalon (midbrain)
- Rhombencephalon (hindbrain)
10
Q
What are the secondary brain vesicles? When do they develop?
A
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
11
Q
The central lumen in each of the secondary brain vesicles take on a unique morphology, creating the _____
A
The central lumen in each of the secondary brain vesicles take on a unique morphology, creating the ventricular system (spaces for CSF)
12
Q
Secondary Brain Vesicles LABEL THE IMAGE SLIDE 6
A
LABEL THE IMAGE SLIDE 6
13
Q
What are the 2 brain flexures? Where are they located?
A
-
Mesencephalic flexure
- at the midbrain-hindbrain boundary
-
Pontine flexure
- at the metencephalon/myelencephalon boundary (between the two divisions of the hindbrain/rhombencephalon)
14
Q
The midbrain-hindbrain boundary function:
A
The midbrain-hindbrain boundary (MHB) functions as an organizing centre for mid/hindbrain development
15
Q
The ventral bend at the midbrain/hindbrain boundary is called the:
A
Mesencephalic flexure
16
Q
The posterior bend at the metencephalon/myelencephalon boundary is the _____
What happens at this region?
A
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
17
Q
The _______ dictate orientation of the brain
A
The flexures dictate orientation of the brain
18
Q
________ overgrows diencephalon and midbrain. _____ overgrows much of the hindbrain
A
telenchephalon overgrows diencephalon and midbrain. cerebellum overgrows much of the hindbrain
19
Q
What region of the brain makes gyri and sulci?
A
Telencephalon
20
Q
The early neural tube is ________
These cells are anchored at both the ___ and ____ surface
A
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
21
Q
What is interkinetic nuclear migration?
A
- 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
22
Q
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 _______
A
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
23
Q
Neuroepithelial cells can divide ______ or _____
Symmetric divisions occur early to ______ or late to ___
Most divisions are _____
A
- 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)
24
Q
How do neuroepithelial cells give rise to neurons, glia and ependymal cells (spatially or temporally (sequentially))
A
Neuroepithelial cells give rise sequentially to neurons, glia, and ependymal cells (line ventricles and make CSF)
25
Most neuroepithelial cells terminally differentiate as _____ or \_\_\_\_\_
SLIDE 12
Most neuroepithelial cells terminally differentiate as _ependymal cells_ or _astrocytes (glia)_
26
\_\_\_\_\_\_\_\_ 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)
27
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
28
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_
29
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
30
* 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
31
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_
32
\_\_\_\_\_\_\_\_\_ 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
33
# 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
34
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
35
LABEL THE SPINAL CORD
label the spinal cord
36
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
37
* 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_
38
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_
39
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
40
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
41
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
42
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)_
43
\_\_\_\_\_\_\_ 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
44
_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
45
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
46
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
47
Label the image Spinal Nerves
slide 25
48
The _______ determines the segmental pattern of the spinal nerves
The _sclerotome_ determines the segmental pattern of the spinal nerves
49
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_
50
Sympathetic neurons form at levels \_\_\_\_\_\_
Parasympathetic neurons form at level \_\_\_\_
Sympathetic neurons form at levels _T1-L2_
Parasympathetic neurons form at _sacral region_
51
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
52
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
53
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_
54
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_
55
Where would you find the parasympathetic ganglia?
Parasympathetic ganglia are in variable locations near the organs
56
Label:
57
Neurons in the spinal cord send out axons which travel to? (3)
Establishing the proper _______ of the nervous system is essential to its functioning
Neurons in the spinal cord send out axons, some of which travel into the periphery, some just connect to nearby neurons within the spinal cord, and some travel to the brain.
Establishing the proper connectivity of the nervous system is essential to its functioning
58
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
59
Axon guidance molecules can be: (4)
* Inhibitory or attractive
* Secreted or membrane bound
60
The response of a growth cone to a guidance molecule depends on many factors, including:
* \_\_\_\_\_\_\_\_
* \_\_\_\_\_\_\_\_
* \_\_\_\_\_\_\_\_
The response of a growth cone to a guidance molecule depends on many factors, including:
* _the receptors expressed by the growth cone_
* _the internal state of the growth cone_
* _other molecules present in the environment_
Therefore, the same guidance cue can be seen as inhibitory to one growth cone, attractive to another growth cone, and ignored by a third growth cone
A single growth cone can change its responsiveness to a cue over time
61
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
62
Axons that cross the midline are called:
Axons that cross the midline are called: Commissural axons
63
In the spinal cord, commissural axons are first repelled _____ by \_\_\_\_\_\_
In the spinal cord, commissural axons are first repelled _ventrally_ by _BMPs_
64
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
65
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
66
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
67
In most regions of the CNS and PNS, excess neurons are produced, what happens to these?
In most regions of the CNS and PNS, excess neurons are produced and some subsequently die by apoptosis.
68
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
69
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
70
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
71
Positional changes in the spinal cord:
* In embryo, SC runs entire length of \_\_\_\_\_\_
* _______ grows faster than _____ (how does this change positioning)
*
Positional changes in the spinal cord:
* In embryo, SC runs entire length of _vertebral column and each level matches_
* _Vertical column_ grows faster than _Spinal Cord_
* At birth, the end of the spinal cord lies at L3
* In adults, it's at L1/L2
72
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_
73
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
74
What happens if the terminal filum is too taut?
* Terminal filum: piece of pia mater that extends caudally to anchor the SC at the first coccygeal vertebra
* If it's too taut:
* Tethered cord syndrome may result
75
Label:
76
Label:
77
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
78
Rhombomeres appear in the ____ and disappear in the \_\_\_\_
Rhombomeres appear in the _4th week_ and disappear in the _6th week_
* Temporary segregation appearing around when the transition from metencephalon to myelencephalon occurs
* Happens early, just after neural tube forms
* Repel eachother - self organize
79
How many cranial nerves are associated with the hindbrain?
8 of 12 cranial nerves are associated with the hindbrain
80
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
81
* 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
82
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
83
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
84
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_
85
What happens to the surrounding tissue when the dorsal side of the fourth ventricle splays open, giving the hindbrain a diamond shape and forming the 4th ventricle?
The surrounding tissues rotate → gives rise to the rhombic lip: a proliferative zone surrounding the 4th ventricle
86
The region of the brain that controls basic functions and resembles the spinal cord in organization:
The brainstem
87
What are the three parts to the brainstem and from which primitive ventricle do they arise?
* Medulla (myelencephalon)
* Pons (part of metencephalon)
* Midbrain (mesencephalon)
88
Out of 12 cranial nerves, ___ have nuclei in the brainstem
2 from \_\_\_\_\_
8 from \_\_\_\_\_
Out of 12 cranial nerves, _10_ have nuclei in the brainstem
2 from _midbrain_
8 from _hindbrain_
89
PNS tissue is a mix of _____ and \_\_\_\_\_\_
PNS tissue is a mix of _Neural crest cells_ and _neurogenic placode_
“recall both neural crest and ectodermal (neurogenic) placodes contribute to cranial nerve sensory and autonomic ganglia”
90
\_\_\_\_\_/\_\_\_\_\_ are displaced laterally upon formation of the 4th ventricle
_alar plates/dorsal columns_ are displaced laterally upon formation of the 4th ventricle
91
Where the roof plate meets neural tissue is the \_\_\_\_\_\_\_
Where the roof plate meets neural tissue is the _rhombic lip (upper/lower)_
92
The Rhombic lip makes \_\_\_\_\_
Cerebellum
93
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
94
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_
95
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
96
Radially migrating neurons sometimes use _____ as scaffolds for migration
Radially migrating neurons sometimes use _radial glial cells_ as scaffolds for migration
97
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
98
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
99
The hindbrain has 2 distinct proliferative zones: the _____ and \_\_\_\_\_\_
The hindbrain has 2 distinct proliferative zones: the _ventricular zone_ and _rhombic lip_
100
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)
101
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)_
102
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)_
103
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)_
104
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_
105
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
106
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
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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_
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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
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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
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The cerebellum develops extensive _____ and is divided into ____ with specific functions
The cerebellum develops extensive _foliation_ and is divided into _lobes_ with specific functions
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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
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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)_
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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
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Telencephalon overgrows \_\_\_\_\_\_\_
Slide 32B
Telencephalon overgrows _diencephalon_
* telencephalon = cerebral hemispheres
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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
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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
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The cerebral cortex started out as ____ (just like the spinal cord/anywhere in neural tube)
The cerebral cortex started out as _pseudostratified neuroepithelium_ (just like the spinal cord/anywhere in neural tube)
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What type of neuronal development/patterning occurs in the cerebral cortex (temporal or spatial)
* Temporal Patterning - waves w/ dif identities
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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)_
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Radial glia cells have two functions:
1. Stem cells
2. Glial highway → help migrating neurons
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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)
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What is the subventricular zone?
* Second proliferative zone basal to VZ that contains neuroblasts and gliablasts
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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
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37B
Label the layers of the cortex
Label the layers of the cortex
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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*
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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*
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SLIDE 39B
Neurons generated by radial migration are mainly ______ (excitatory/inhibitory)
SLIDE 39B
Neurons generated by radial migration are mainly _excitatory (glutamatergic) pyramidal neurons_
* Inhibitory (Gabaergic) nn are made elsewhere (ganglionic eminence of ventral telencephalon) and brought in (tangentially)
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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**
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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
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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
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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_
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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_
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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_
