Neuroembryology: Nervous System Development Flashcards
What are the main components of neural development (5)
- Birth and differentiation of the neurons
- Migration of neurons from birthplace to final destination
- Outgrowth of axons from the neurons and the formation of synapses with post synaptic neighbors
- Pruning of neurons related to experience
- Changes in synapses related to learning and memory
What is the first system that can be delineated in embryo
The nervous system
What are the 3 embryonic germ layers
- Ectoderm
- Mesoderm
- Endoderm
What does the ectoderm end up forming (7)
- Nervous system
- Epidermis of skin and it’s derivatives (sweat, hair, receptors)
- Cornea and lens
- Adrenal medulla
- Epithelium of pineal and posterior pituitary
- Tooth enamel
- Epithelial lining of mouth and anus
What does the mesoderm end up forming (11)
- Notochord
- Skeletal system
- Muscular system
- Muscular layer of stomach and intestine
- Excretory system
- Circulatory and lymphatics
- Reproductive
- Dermis of skin
- Lining of body cavity
- Adrenal cortex
- Kidneys and heart
What does the endoderm end up forming (6)
- Epithelial lining of digestive tract and respiratory system
- Lining or urethra, urinary bladder, and reproductive system
- Liver
- Pancreas
- Thymus
- Thyroid and parathyroid
What does the notochord do
Secretes chemicals that prevent the nervous system from developing until the time is right
What does the notochord do when the time is right to start neural development
Secretes the protein sonic hedgehog
What does sonic hedgehog do
Inhibits the inhibitor preventing neural development
When does sonic hedgehog show up after
2-3 weeks after conception
At what stage does the formation of the vertebrate nervous system take place
Gastrula stages
What happens to the dorsal ectoderm
Thickens bilaterally becoming committed to the nervous system
What is the thicken of the dorsal ectoderm called
The neural plate
Where does neural epithelium cover
The notochord
What are the 3 stages of development that the neuroectoderm undergoes
- It transforms into the neural plate
- It invaginates to form the neural groove
- The folds of the groove eventually fuse to form the neural tube
What ultimately forms the nervous system
The neural tube
How many sections does the rostral portion of the neural tube form
3
What forms the PNS
The neural crest
When does the neuroectoderm begin to fold
18 days after conception
When does the neuroectoderm begin to close into a tube in the cervical area
Around day 20
Which way does the neuroectoderm zip up and what day
Rostral to caudal at day 28
What does the neural crest form (6)
- Spinal dorsal root ganglia
- Ganglia of the ANS
- Cranial nerves
- Meninges
- Schwann cells
- Pigment cells in the skin
What does the neural tube form (4)
- Brain
- Spinal cord and motor neurons
- Retina
- Posterior pituitary
What do somites develop into
Sympathetic chain
How does neural development occur
Based on experiences
What are the 3 primary vesicles
- Proencephalon
- Mesencephalon
- Rhombencephalon
What is a flexure
A curve that occurs because not all of the cells are dividing at the same rate
Where does the most proliferation or nerve cell precursors occur in the neural tube
Inner to outer surface
Which end of the neural tube does the brain emerge from
The rostral end
Where does the forebrain sit during development
On top of the heart
What are the 2 flexures that develop in the central nervous system in embryo
Cephalic and cervical flexures
What does the proencephalon form
Telecephalon and diencephalon
What makes up the telecephalon (4)
- Cerebral cortex
- Subcortical white matter
- Basal ganglia
- Basal forebrain nuclei
What makes up the diencephalon (3)
- Epithalamus
- Thalamus
- Hypothalamus
What is the proencephalon also called
The forebrain
What is the mesencephalon also called
The midbrain
What makes up the mesencephalon (3)
- Cerebral peduncles
- Midbrain tectum
- Midbrain tegmentum
What is the rhombencephalon also called
The hindbrain
What makes up the rhombencephalon (2)
- Metencephalon
2. Myelencephalon
What does the metencephalon form (2)
- Pons
2. Cerebellum
What does the myelencephalon form (1)
Medulla
What is another name for the pontomedullary junction
Bulbopontene junction
What is it called when the brain and spinal cord are completely open
Craniorachischisis
What is it called when the brain is open and there is the lack of a skull
Anencephaly
What is it called when there is herniation of the meninges and potentially the brain
Encephalocele
What is it called when the occipital skull and spine defects with extreme retroflexion of the head
Inencephaly (head permanently extended)
What is a closed asymptomatic neural tube defect in which some of the vertebrae are not completely closed
Spina bifida occulta
What is a deficiency of at least two vertebral arches covered by lipoma
Closed spinal dysraphism
What is protrusion of the meninges filled with CSF through a defect in the spine
Meningocele
What is an open spinal cord with a meningeal cyst
Myelomeningocele
How do you prevent skull and vertebral arches from not forming
Taking folic acid
What separates the developing gray matter of the mantle layer on lateral walls of the neural tube into basal and alar plates
Sulcus limitans
How far to the alar and basal plates extend
The length of the spinal cord
What is the cerebellum a greatly expanded outgrowth of
The alar plate of the mesencephalon
Where does the alar plate extend
Only through the mesencephalon
What do cells within the alar plate develop into
Afferent and interneurons
Are afferent fibers sensory or motor
Sensory
What are the 3 types of afferent fibers developed by the alar plate
- General sensory afferents
- Special sensory afferents
- Visceral sensory afferents
What do cells in the basal plate develop into
Efferent neurons
Are efferent neurons sensory or motor
Motor
What are the 3 types of efferent fibers developed by the basal plate
- General motor efferents
- Special motor efferents
- Visceral motor efferents
What forms the cranial nerve nuclei
The basal and alar plates
Where does the alar plate lie in relation to the basal plate after thinning of the mesencephalic roof
Dorsolateral
In the spinal cord where is the alar plate located
More dorsal
What does the alar plate yield in the spinal cord
Gray neurons for sensory processing
In the spinal cord where is the basal plate located
Ventral
What does the basal plate form in the spinal cord
Motor area of the cord
Why do we have the cauda equina
The vertebrae continue to grow after the spinal cord stops growing making the spinal column longer than the spinal cord
What causes folding of the tissue in the brain
Rapid proliferation