Week 1 CNS & Skull Embryology- Ach Flashcards
What three embryonic sources does the entire nervous system derive from?
Neural tube
Neural Crest
Placodes
(all ECTODERM) in origin
Describe development of neural tube
- Notochord stimulates ectoderm differentiation into neural plate
- Neural folds
- Neural groove
- Week 4 fusion of neural tube, begins centrally and moves both directions
What are neuropores?
Located on each end of the neural tube
-communicated with amniotic fluid
What is the space with in the neural tube called?
Neural canal
What does the neural tube form?
Brain AND spinal cord
What are neural crest cells and what do they form?
- they are motile neuroectodermal cells
- migrate through out embryo
- Forms PNS, and a wide variety of non-neuronal structures
What does the neural canal form?
Ventricles of the brain and Central canal of the spinal cord
What are the layers of the neural tube?
- Ventricular layer
- Intermediate layer
- Marginal layer
What does the ventricular layer of the neural tube become?
- Rapidly dividing neuroepithelial cells
- Differentiate into neurons and glial cells
- Become ependyma (single layer of cells lining the central canal of the spinal cord)
What does the intermediate layer of the neural tube become?
- Will become GRAY MATTER of the spinal cord (dorsal, ventral and lateral horns)
- NOTE: CONTAINS ALL SPINAL CORD NERVE CELL BODIES
What does the marginal layer of the neural tube become?
Becomes the WHITE matter of the spinal cord
What is the difference between the mitotic ability of Neurons and glial cells?
- Glial cells can divide
- Neurons loose their ability when they develop processes (some rare examples they do)
What plates form with-in the intermediate layer of the neural tube?
Alar and basal plates
What divides the alar and basal plates?
Sulcus limitans
-longitudinal groove in the lumen
What does the alar plate form and where is it located?
Alar is dorsal
- forms second order neurons
- SENSORY/AFFERENT neurons (primarily of the dorsal horn)
What does the basal plate form and where is it located?
Basal is ventral
-Forms motor neurons of the VENTRAL (large motor neurons tha innervate skeletal muscle) and LATERAL horns (pre-ganglionic neurons of the sympathetic nervous system)
Why are the roof and floor plates of the neural tube important?
Contain NO neuroblasts
-Become routes for axons to cross the midline of the spinal cord!!!
Where would you find the cell bodies of motor neurons in the ventral horn? (embryonically)
BASAL PLATE
-will send out neurites (multiple cytoplasmic processses) that become axon/dendrites
Where would you find the cell bodies of sensory neurons in the dorsal horn? (embryonically)
ALAR PLATE
Where are the dorsal root ganglia derived from?
Neural crest
Note: the neurons are PRIMARY afferents
What cell myelinate the CNS and PNS
CNS- Oligodendrocytes
PNS- Schwann cells
When does myelination begin?
4 months of prenatal development
Why do you see a positive Babinski sign in infants?
Toes extend due to incomplete myelination. (if present in adults indicated CNS pathology)
At birth where is the end of the spinal cord located?
L2 or L3
In the adult where does the spinal cord terminate?
inferior border of L1
What are the three primary brain vesicles?
Prosencephalon (Forebrain)
Mesencephalon (Midbrain)
Rhombencephalon (Hindbrain)