Development of the Brain Flashcards
The neural plate (from neuroectoderm) and neural groove develop on the posterior aspect of the trilaminar embryo at _____ weeks. This is induced by the notochord.
3
Neurulation begins at the 4th week (22-23 days). The cranial 2/3 will give rise to the 4th pair of somites, which is the future _______. The caudal 1/3 will give rise to the future ______ ______.
Brain
Spinal Cord
The neural tube first forms at the ______ somite. It proceeds cranially and caudally until only the neuropores remain. The cranial (rostral) neuropore closes at day ______, and the caudal neuropore closes at day _______.
25
27
The brain develops during the 3rd week from the ______ ______, cranial to the 4th pair of somites.
Neural tube
Fusion of neural folds in the cranial region and closure of rostral neuropore form the primary ______ ______.
Brain vesicles
What does the Telencephalon give rise to?
Cerebral hemispheres
Lateral ventricles
What does the Diencephalon give rise to?
Thalamus
Hypothalamus
Epithalamus
3rd ventricle
The forebrain, also called the _________, will give rise to the ________ and ________.
Prosencephalon
Telencephalon
Diencephalon
The midbrain, also called the _________, gives rise to the _______ and _______.
Mesencephalon
Midbrain
Aqueduct
The hindbrain, also called the __________, will give rise to the _________ and _________.
Rhombencephalon
Metencephalon
Myelencephalon
What does the Metencephalon give rise to?
Pons
Cerebellum
Upper part of 4th ventricle
What does the Myelencephalon give rise to?
Medulla
Spinal Cord
Lower part of 4th ventricle
During which week do the secondary brain vesicles form (i.e., forebrain divides into telencephalon and diencephalon, etc.)?
5th week
During the 5th week, the embryonic brain grows rapidly and bends ventrally with the head fold. Bending produces the _______ _______ (midbrain) and the ________ _______ (hindbrain-SC junction). They both fold in the same direction, flexing toward the trunk.
Midbrain Flexure (Mesencephalic Flexure) Cervical Flexure
Unequal growth produces the ________ ________, which folds in the opposite direction, like extension, at the meten-myelencephalon junction.
Pontine Flexure
Brain flexures produce considerable variation position of the…
Gray and white matter
This is what demarcates the hindbrain from the spinal cord, and its junction is arbitrarily defined as the level of superior rootlet of C1 (roughly located at foramen magnum).
Cervical Flexure
This is what divides the hindbrain into the metencephalon (rostral) and myelencephalon (caudal).
Pontine Flexure
***Remember, the myelencephalon gives us the medulla and the metencephalon gives us the pons and cerebellum.
What makes up the cavity of the hindbrain?
4th ventricle and central canal in the medulla
In the caudal myelencephalon, neuroblasts in the alar plates migrate into the marginal zone. This forms the _______ ______ and _______ _______, which are sensory nuclei that associate with their paired, afferent tracts.
Nuclei Gracilus
Nuclei Cuneatus
***Remember, alar = afferent and basal = efferent!
In the myelencephalon, the _________ (ventral) consist of CST fibers.
Pyramids
The rostral myelencephalon is wide and flat. The Pontine Flexure cause the walls of the medulla to move laterally and the roof plate is greatly thinned. This causes the (ALAR/BASAL) plates to become lateral to the (ALAR/BASAL) plates, making motor nuclei develop medial to the sensory nuclei.
Alar
Basal
Neuroblasts (from neuroectoderm) in the basal plate develop into motor neurons. Nuclei organize into cell columns on each side, which have what modalities?
General Somatic Efferent (GSE)
Special Visceral Efferent (SVE - Branchial)
General Visceral Efferent (GVE)
Neuroblasts (from neuroectoderm) in the alar plates of the medulla form neurons that are arranged in columns on each side. What are their modalities?
General Visceral Afferent (GVA)
Special Visceral Afferent (SVA)
General Somatic Afferent (GSA)
Special Somatic Afferent (SSA)
This basal column consists of the nucleus of the hypoglossal nerve in the caudal-most rhombencephalon, that of nerve VI more cranially in the rhombencephalon, that of nerve IV in the most cranial rhombencephalon (later displaced into the caudal midbrain), and that of nerve III in the mesencephalon.
GSE
This basal columns contains three nuclei serving nerves V, VII, and IX through XI and is confined to the rhombencephalon. The nuclei serving nerves V and VII are located cranially in the rhombencephalon and caudally the elongated Nucleus Ambiguus supplies fibers for nerves IX, X, and XI.
SVE (Branchial)
This basal column includes two nuclei located in the rhombencephalon. The salivary nuclei provide preganglionic parasympathetic innervation to the salivary and lacrimal glands via nerves VII and IX. Just caudal to this nucleus is the dorsal parasympathetic neurons innervating the viscera. The Edinger-Westphal nucleus (III) is located in the mesencephalon.
GVE (Parasympathetic)
This alar column consists of the nucleus that receives interoceptive information via the glossopharyngeal nerve (IX) and the vagus nerve (X).
GVA
This alar column consists of the nucleus of the tractus solitarius, which receives taste impulses via the facial (VII), glossopharyngeal (IX), and vagus (X) nerves.
SVA
This alar column consists of the neurons that receive impulses of general sensation form areas of the face served by the trigeminal (V) and facial (VII) nerves and from the oral, nasal, external auditory, and pharyngeal and laryngeal cavities (V, VII, IX, and X).
GSA
This alar column consists of the cochlear and vestibular nuclei, which subserve the special senses of balance and hearing (VIII).
SSA
The Pontine Flexure forces walls of the Pons laterally, which spreads the gray matter in the floor of the…
4th ventricle
This develops form the dorsal parts of alar plates.
Cerebellum
Cerebellar _________ project into the 4th ventricle and fuse in the median plane. They overgrow the rostral 4th ventricle and overlap pons/medulla.
Swellings
The Ependymal roof of the 4th ventricle is covered externally by _______ _______ (derived form hindbrain mesenchyme).
Pia Mater
Pia Mater + Ependymal roof = _______ _______. This is a sheet of pia covering the lower part of the 4th ventricle.
Tela Choroidea
The Tela Choroidea invaginates in 4th ventricle to form the…
Choroid Plexus
The epithelial lining of the Choroid Plexus is derived from _________, and the stroma develops from _________ cells. They secrete ventricular fluid, which becomes CSF.
Neuroepithelium
Mesenchymal
The roof of the 4th ventricle evaginates in three locations, which rupture forming the ________ _______ and _______ _______. These permit the CSF to enter the Subarachnoid Space from the 4th ventricle.
Median Aperture
Lateral Aperture
In the midbrain, neuroblasts of the alar plates migraine into the tectum and form the…
Superior and Inferior Colliculi
In the midbrain, neuroblasts of the basal plates form ________ nuclei (include red nuclei, reticular nuclei, CN III and IV nuclei).
Tegmental
In the midbrain, fibers growing from the cerebral cortex form the _______ _______.
Cerebral Peduncles (Crus Cerebri)
In the midbrain, the neural canal narrows and forms the ________ ________, which connects the 3rd ventricle to the 4th ventricle.
Cerebral Aqueduct
This component of the midbrain is still arguable. Could be basal plate or alar plate cells that migrate ventrally.
Substantia nigra
The diencephalon consists of 3 swellings in the lateral walls of the 3rd ventricle that form the thalamus, hypothalamus, and epithalamus. The ________ _______ separates the thalamus and epithalamus, and the ________ ________ separates the thalamus and hypothalamus.
Epithalamic sulcus
Hypothalamic sulcus
The Thalamus develops on each side of the 3rd ventricle and bulges into its cavity. It fuses at the midline in 70 percent of brains, forming the ________ _______. The bridge is absent in about 20 percent of brains.
Interthalamic Adhesion
The hypothalamus arises from neuroblasts in the intermediate zone. Endocrine and homeostatic nuclei develop on it, as well as _________ _________ form on its ventral surface.
Mammillary bodies
This develops from the roof and dorsal portions of the lateral wall. Its swellings are large, but become relatively small.
Epithalamus
This develops as a median diverticulum of the caudal part of the roof of the diencephalon. The proliferation of cells in its walls converts it into a solid, cone-shaped gland. Functions with sleep and wakefulness (melatonin).
Pineal Gland
To develop the pituitary gland, there is an upgrowth of the roof of the stomodeum called ________ _______, and a downgrowth from the diencephalon called the ________ ________.
Hypophyseal Diverticulum (forms anterior pituitary) Neurohypophyseal Diverticulum (forms posterior pituitary)
This is what passes between developing bones of the cranium and attaches the pituitary gland to the hypothalamus (specifically the posterior pituitary attaches to hypothalamus).
Infundibular stalk
The Hypophyseal Diverticulum is made of adenohypophysis (glandular tissue). This makes up what parts?
Pars anterior
Pars tuberalis
Pars intermedia
***Forms anterior lobe of pituitary
The Neurohypophyseal Diverticulum is made of neurohypophysis (nervous tissue). This makes up what parts?
Pars nervosa
Infundibular stem
Median eminence
***Forms posterior lobe of pituitary – connects to hypothalamus
Medial wall of cerebral hemisphere (telencephalon) becomes very thin and is continuous with roof of 3rd ventricle. ______ ______ forms at this site.
Choroid Plexus
Cerebral hemispheres expand and cover the diencephalon, midbrain, and hindbrain. Mesenchyme trapped in the longitudinal fissure gives rise to the…
Falx cerebri
Cavities of the telencephalon and diencephalon form the…
3rd ventricle
This is caused by incomplete separation of the cerebral hemispheres. Defects in the forebrain development often cause facial anomalies resulting form a reduction of the FNP. Cyclopia, premaxillary genesis, proboscis, single-nostril, hypotelorism, and facial clefts. Severe and common defect.
Holoprosencephaly (HPE)
These are groups of nerve fibers interconnecting the cerebral hemispheres.
Cerebral commissures
This commissure interconnects the olfactory bulb with the hemispheres.
Anterior commissure
This commissure connects the hippocampal formations.
Hippocampal commissure
This forms, linking the cerebral hemispheres along their length. The anterior portion forms first, posterior portions forms in fetal life.
Corpus Callosum
The Lamina Terminalis (at rostral end of forebrain) is stretched, forming the _______ _______, a thin plate of brain tissue containing nerve cells and fibers.
Septum Pellucidum
This commissure connects the right and left temporal lobes.
Posterior commissure
T/F. Agenesis of the Corpus Callosum (partial or complete absence) may be asymptomatic, but seizures and mental deficiency are common. Associated with more than 50 human congenital syndromes.
True
***If born with corpus callosum and it’s cut, then will definitely result in mental deficits. If born without it, likely to be asymptomatic.
The cortex is initially smooth, but growth results in development of sulci and gyri. Gyri result from infolding of the cortex. The purpose of sulci and gyri were to…
Increase surface area (without increasing volume of neurocranium)
Brain at birth is only about 25 percent of its adult volume. Postnatal growth is from neurons increasing in size and _________ of axons. Brain reaches its final size at _______ years old.
Myelination
7
In the cerebral cortex development, they have specific zones which are…
Ventricular
Intermediate
Marginzal
Subventricular
***Grows inside out (like a tree)
Cortical layers are laid down in a sequence from deep to superficial. Neurons migrate through the deeper layer and exit, to establish more superficial layers. “Inside-Out” development. This means superficial layers are (NEW/OLD) and deep layers are (NEW/OLD).
Old
New
This occurs when there is incomplete neuronal migration to the cerebral cortex during 3-4 months of gestation. “Smooth” cerebral surface exhibiting pachygyria (broad, thick gyri), agyria, neuronal heterotropia (cells in aberrant positions), and enlarged ventricles and malformation of corpus callosum. Will initially appear normal but later develop seizures, mental deficiency, and mild spastic quadriplegia.
Lissencephaly
This is a neurodevelopmental disorder where calvaria and brain are small, but the face is normal sized. Have significant mental deficiencies due to brain underdevelopment. Results from reduction in brain growth (inadequate pressure from the growing brain leads to a small neurocranium). Causes include ionizing radiation, infectious agents, maternal alcohol abuse, etc.
Microcephaly
