Development of the Brain Flashcards
1
Q
3 Steps of Neurulation
A
(1) Notochord forms from mesoderm cells after gastrulation is complete
(2) Signals from notochord cause inward folding of ectoderm at the neural plate
(3) Ends of neural plate fuse and disconnect to form an autonomous neural tube
2
Q
When does brain development occur?
A
During the 3rd week from the NT (cranial to 4th pair of somites)
3
Q
Fusion of neural folds in cranial region and closure of rostral neuropore form:
A
Primary Vesicles (n=3)
4
Q
When do secondary vesicles form? How many are there?
A
- 5th week
- 5
5
Q
What are the 3 primary vesicles?
A
(1) Forebrain (Prosencephalon)
(2) Midbrain (Mesencephalon)
(3) Hindbrain (Rhombencephalon)
6
Q
What are the 5 secondary vesicles?
A
(1) Telencephalon
(2) Diencephalon
(3) Mesencephalon
(4) Metencephalon
(5) Myelencephalon
7
Q
What secondary vesicles form from the Forebrain primary vesicle?
A
- Telencephalon
- Diencephalon
8
Q
What secondary vesicle forms from the Midbrain?
A
Mesencephalon
9
Q
What secondary vesicles form from the Hindbrain?
A
- Metencephalon
- Myelencephalon
10
Q
Adult Derivatives of the Telencephalon:
(1) Wall
(2) Cavities
A
(1) Wall: cerebral hemispheres
(2) Cavities: lateral ventricles
11
Q
Adult Derivatives of the Diencephalon:
(1) Wall
(2) Cavities
A
(1) Walls: thalami, etc
(2) Cavities: third ventricle
12
Q
Adult Derivatives of the Mesencephalon:
(1) Wall
(2) Cavities
A
(1) Walls: midbrain
(2) Cavities: aqueduct
13
Q
Adult Derivatives of the Metencephalon:
(1) Wall
(2) Cavities
A
(1) Walls: pons and cerebellum
(2) Cavities: upper (rostral) part of 4th ventricle
14
Q
Adult Derivatives of the Myelencephalon:
(1) Wall
(2) Cavities
A
(1) Walls: medulla
(2) Cavities: lower part of 4th ventricle
15
Q
Space of ___ cavity is limited by growth of the ___ is extensive
A
- Cranial cavity
- Brain
16
Q
Brain Flexures
A
- Form as primary vesicles –> secondary vesicles (5th week)
- Specific locations in the NT where the brain folds to fit in the skull
17
Q
How many brain flexures are there?
A
- 2 ventral flexures
- 1 dorsal flexure
18
Q
What are the two Ventral Flexures?
A
- Mesencephalic Flexure
- Cervical Flexure
19
Q
Pontine Flexure
A
- Dorsal Flexure
- Divides metencephalon (rostral) from myelencephalon (caudal)
20
Q
Cervical Flexure
A
Demarcates (forms the boundary) hindbrain from spinal cord (superior rootlet of C1/foramen magnum)
20
Q
Cervical Flexure
A
Demarcates (forms the boundary) hindbrain from spinal cord (superior rootlet of C1/foramen magnum)
21
Q
Mesencephalic Flexure
A
- Located between the Prosencephalon and Mesencephalon
- It is the midbrain flexure
22
Q
Neuroblasts in the Ventral Zone divide to form:
A
Neurons
23
Q
Neuroblasts in the Alar Plates form the ___ columns
A
Lateral
24
Alar Plate gives rise to:
- Sensory Nuclei
- Develops into the dorsal horns
25
4 Lateral Columns (M --> L)
(1) General Visceral Afferent
(2) Special Visceral Afferent
(3) General Somatic Afferent
(4) Special Somatic Afferent
26
Neuroblasts in the Basal Plates form the ___ columns
Medial
27
3 Medial Columns (M --> L)
(1) General Somatic Efferent
(2) Special Visceral Efferent
(3) General Visceral Efferent
28
In the caudal region of the Myelencephalon, Alar neuroblasts migrate into the ___ zone to form ___ ___ and ___ ____
- Marginal Zone
- Nucleus Gracilis
- Nucleus Cuneatus
29
In the Myelencephalon, dorsal sensory nuclei associate with afferent tracts of the:
Dorsal Column - Medial Lemniscus Pathway (DCML)
30
In the Myelencephalon, Pyramids (ventral) consist of:
Corticospinal Tract Fibers
31
Rostral region of the Myelencephalon is wide and flat due to the:
Pontine Flexure
- causes walls to move laterally
- roof plate is greatly thinned
- cavity is part of 4th ventricle
32
Pontine Flexures force walls of the ___ laterally
Pons
33
Cerebellum develops from:
Dorsal parts of Alar Plates form the Cerebellar Swelling (primordium of cerebellum)
34
Cerebellar swellings project into the ___ ventricle and fuse in the median plane, causing them to overgrow the ___ ___ ___, ___ and ___.
- 4th Ventricle
- Rostral 4th Ventricle, Pons, Medulla
35
What nuclei form from Alar Plates?
- Cerebellar Nuclei
- Pontine Nuclei
- Cochlear Nuclei
36
Another name for Anterior Lobe of Cerebellum
Paleocerebellum
37
Another name for Posterior Lobe of Cerebellum
Neocerebellum
38
Structures of Pons/Cerebellum that also form from Metencephalon
- Cerebellar hemisphere
- Vermis
- Posterolateral Fissure
- Flocculus
39
Structures of Medulla that also form from Myelencephalon
- Gracile Tubercle
- Cuneate Tubercle
- Obex
40
Ependymal roof of 4th ventricle is covered with:
Pia Mater from Hindbrain Mesenchyme
41
___ + ___ = Tela Choroidea
Pia + Ependymal Roof
42
Tela Choroidea
- Proliferates and invests into 4th ventricle
- Forms choroid plexus and secretes ventricular fluid
43
Roof of 4th Ventricle "balloons" to form ___ and ___ out pockets which eventually rupture to form ___ and ___ ____
- Medial and Lateral
- Medial and LAteral Apertures (openings in dural sinus that allows CSF to circulate)
44
Choroid Plexus also forms in roof of __ ventricle and medial walls of ___ ventricles
- 3rd
- Lateral
45
In Midbrain, alar neuroblasts migrate into the __ and then form ___ and ___ ___
- Tectum
- Superior and Inferior Colliculi
46
In Midbrain, Basal neuroblasts form:
Tegmental Nuclei
47
Tegmental Nuclei formed from Basal Neuroblasts:
- Red Nuclei
- REticular Nuclei
- CN III Nuclei
- CN IV Nuclei
- Substantia Nigra (MAYBE???)
48
Neural canal in Midbrain narrows and forms:
Cerebral Aqueduct
49
What ventricles does the Cerebral Aqueduct connect?
3rd and 4th Ventricles
50
In Midbrain, fibers from cerebral cortex form:
Cerebral Peduncles (Crus Cerebri)
51
In the Diencephalon, what structures form from the neuronal swellings in lateral walls of the 3rd ventricle?
- Thalamus
- Hypothalamus
- Epithalamus
52
Epithalamus and Pineal Gland develop from the:
Roof of the Diencephalon
53
Interthalamic Adhesion
- Forms when Thalamus develops and bulges into cavity, then fuses at midline
- Occurs in 70% of brains
54
What nuclei develop from the Hypothalamus?
Endocrine and Homeostatic Nuclei
55
What forms on the ventral surface of the Hypothalamus?
Mammillary Bodies
56
What sulcus is located between the Epithalamus and the Thalamus?
Epithalamic Sulcus
57
What sulcus is located between the Thalamus and Hypothalamus?
Hypothalamic Sulcus
58
What are the two embryonic sources of the Pituitary Gland?
(1) Hypophyseal Diverticulum (Rathke Pouch)
(2) Neurohypophyseal Diverticulum
59
Hypophyseal Diverticulum
- Upgrowth of roof of primitive mouth (grows up from roof of mouth towards brain)
- Derived from surface/oral ectoderm
60
Neurohypophyseal Diverticulum
- Downgrowth of diencephalon
- Derived from neuroectoderm
61
Infundibulum
- Derived from neurohypophyseal diverticulum (keeps the neurohypophyseal part attached to the diencephalon)
- Passes between developing bones of the cranium
62
Development of Hypophyseal Diverticulum
(1) Projects from roof of primitive mouth by 3rd week
(2) Constricts its attachment from oral cavity
(3) Passes through the cranium and contacts the infundibulum
(4) Regresses from oral cavity during 6th week
63
Derivatives of Hypophyseal Diverticulum (from Roof of Stomodeum)
(1) Tissue Type:
(2) Part:
(3) Lobe:
(1) Adenohypophysis (Glandular tissue)
(2) Pars Anterior, Pars Tuberalis, Pars Intermedia
(3) Anterior Lobe
64
Derivatives of Neurohypophyseal Diverticulum from Floor of Diencephalon)
(1) Tissue Type:
(2) Part:
(3) Lobe:
(1) Neurohypophysis (nervous tissue)
(2) Pars Nervosa, Infundibular Stem, Median Eminence
(3) Posterior Lobe
65
Telencephalon consists of lateral outpocketings, the ___ ___ and a medial ___ ___
- Cerebral hemispheres
- Medial lamina terminalis
66
Telencephalon Development/Formation of Cerebral Hemispheres
(1) Two hemispheres expand and overgrow the Diencephalon, Midbrain, and Hindbrain
(2) Hemispheres meet each other in the midline and medial surfaces flatten
(3) Basal part of hemispheres grow rapidly and bugle into lateral ventricle to form the corpus striatum
67
What forms the Falx Cerebri?
Mesenchyme from Telencephalon trapped in longitudinal fissure
68
Formation of Corpus Striatum
Basal part of the hemispheres grow rapidly and bulge into lateral ventricle, forming corpus striatum
69
Corpus striatum expands posteriorly and divides into two parts:
(1) Caudate Nucleus
(2) Lentiform Nuclei (= Putamen and Globus Pallidus)
70
How does separation of the Corpus Striatum occur?
- Axons pass to and from cortex of hemispheres, breaking through the corpus striatum
- Fibers bundle and become the Internal Capsule
71
Continuous growth of cerebral hemispheres in all directions results in formation of:
Frontal, Temporal, and Occipital Lobes
72
Holoprosencephaly (HPE)
- Results from incomplete separation of the cerebral hemispheres -- atypical development of the Telencephalon
- Most cases are associated with facial abnormalities (cyclopia, premaxillary agenesis, proboscis, single-nostril, hypotelorism, facial clefts)
- Severe and relatively common defect
73
Main Genetic Loci implicated in Holoprosencephaly:
- SHH***
- GLI
- IHH
- SIX3
- TGIF
- ZIC
- PTCH
All the genetic loci implicated have some role/relationship with SHH (sonic hedgehog signaling)
74
Genetic Implications of Holoprosencephaly
Impaired forebrain development -> impacts frontonasal prominence (FNP) development -> facial anomalies
75
Cerebral Commissures
Groups of nerve fibers interconnecting the cerebral hemispheres
76
When do Cerebral Commissures form?
End of 3rd month
77
In formation of cerebral commissures, use __ ___ as a passageway and extend from roof of __ to optic chiasm
- Lamina Terminalis (Telencephalon)
- Diencephalon
78
What are the 3 main Cerebral Commissures?
(1) Anterior Commissure
(2) Hippocampal Commissure (Fornix)
(3) Corpus Callosum
79
Anterior Commissure
Interconnects the olfactory bulb and related areas within each hemisphere
80
Hippocampal Commissure (Fornix)
Interconnects the hippocampus --> Mammillary body, hypothalamus
81
Habenular and Posterior Commissures
Below and rostral to Pineal Gland
82
Optic Chiasm
- Contains fibers from medial halves of retina
- Allows for binocular vision
83
Agenesis of Corpus Callosum
- Complete or partial absence of the corpus callosum
- Condition may be asymptomatic, but seizures and mental deficiency are common
- Associated with more than 50 human congenital syndromes
84
Cortex is initially ___, but growth results in development of __ and __
- Smooth
- Sulci and Gyri
85
Gyri result from:
Infolding of the cortex
86
Functions of Gyri and Sulci:
Increase the surface area without increasing the volume of the neurocranium
87
Brain at birth is only ___% of its adult volume
25%
88
___ Growth of the brain is from neurons increasing in size and myelination of axons
Postnatal
89
___ neurons are on surface of brain where the ___ neurons are deepest in the brain
- Youngest
- Oldest
90
Initial zones of the Cerebral Hemisphere that seen early in NT:
- Ventricular
- Intermediate
- Marginal Zones
A 4th layer, the Subventricular Zone, appears
91
Cortical layers are laid down in a sequence from ___ to ___
Deep to Superficial
- neurons migrate through deeper layer and exit, to establish more superficial layers --> 'inside out' development
92
Lissencephaly
- Incomplete neuronal migration during 3-4 months of gestation
- Infant will initially appear 'normal' but later develops seizures, profound mental deficiency and mild spastic quadriplegia
- Smooth cerebral surface exhibits: Pachygyria, Agyria, Neuronal Heterotopia, Enlarged ventricles and malformation of the corpus callosum
93
Pachygyria
Broad, thick gyri
94
Agyria
Lack of gyria
95
Neuronal Heterotopia
Cells are in aberrant positions compared to a normal brain --- cells not migrating to the correct position
96
Microcephaly
- Neurodevelopmental disorder where calvaria and brain are small, but face is normal sized
- Results from a reduction in brain growth
- Inadequate pressure from the growing brain leads to a small neurocranium with accompanying mental deficiencies
97
Causes of Microcephaly
- Autosomal recessive primary microcephaly
- Ionizing radiation
- Infectious agents (cytomegalovirus, Zika Virus, rubella virus, Toxoplasma gondii)
- Maternal alcohol use
98
The anterior and posterior neuropores normally close:
During the 4th week of development
99
Cell type that is found in the CNS that is not derived from neuroectoderm:
Microglia
100
Maternal toxoplasmosis may result in:
Microcephaly
101
The sulcus limitans is the groove that separates the:
Alar and Basal Plates
102
The cervical flexure demarcates the:
Hindbrain from the spinal cord
103
What is true of the Prosencephalon? What is not true of it?
TRUE
- It gives rise to the diencephalon and telencephalon
- Its cavity includes the third ventricle and the lateral ventricle
FALSE
- It gives rise to the mesencephalon
104
45 YO man develops Bell's Palsy and has temporary facial paralysis on the entire left side of his face. From what specific level of the CNS do these motor fibers arise?
Metencephalon
105
20 YO woman suffers a stroke after a drug overdose that causes localized damage to the brain stem special somatic afferent column on one side. Sensation from what structure will be compromised?
Inner ear
106
13 YO girl develops a tumor of the anterior pituitary gland, What is the embryonic derivative of this tissue?
Hypophyseal Diverticulum
