BMS1052 Developmental Neurobiology –1 Flashcards
The average brain has:
- Approximately 100 billion neurons,
- 1000 to 5000 billion glial cells, and
- Approximately 60 trillion synapses in the cerebral cortex.
neural crest cell
Neural crest cells (NCC) are multipotent cells induced at the border of the neural plate that subsequently migrate throughout the embryo and later differentiate into multiple cell types contributing to most of the peripheral nervous system and the cranio-facial cartilage and bones, as well as pigment and endocrine
Neural tube defect
Neural tube defects are birth defects of the brain, spine, or spinal cord. They happen in the first month of pregnancy, often before a woman even knows that she is pregnant. … In spina bifida, the fetal spinal column doesn’t close completely. There is usually nerve damage that causes at least some paralysis of the legs
if the top region does not close brain does not develop properly
somites
Somites are blocks of mesoderm that are located on either side of the neural tube in the developing vertebrate embryo. … As the somite matures, the outer cells transform from mesenchymal to epithelial cells, creating a distinct boundary between individual somites.
somites subdivide into the sclerotomes, myotomes, syndetomes and dermatomes that give rise to the vertebrae of the vertebral column, rib cage and part of the occipital bone; skeletal muscle, cartilage, tendons, and skin
Where do neurons come from?
• The developing embryo undergoes gastrulation.
• This creates a three layered embryo.
• Neural tissue develops from the ectoderm, the
top layer of the embryo.
What cells are capable of becoming neurons?
• Signals converge on the middle region of the ectoderm and induce it to become neural tissue.
The middle region will fold up to make neural tube.
The region on the border between ectoderm and the neural plate gives rise to neural crest which migrate away and produce some of the cell for peripheral NS
What is neurulation?
Neurulation – formation of the neural tube
• The neural plate rolls up into a tube.
• The center (lumen) of the tube is filled
with fluid. filled with CSF
Neural tube defects
The neural tube joins up first in the middle, and zippers
up to closure points.
Neural tube defects occur when the neural tube fails to close.
failure of closure the brain doesn’t develop properly
skull doesn’t develop properly
results in spina bifida. a birth defect that occurs when the spine and spinal cord don’t form properly. It’s a type of neural tube defect
Folic acid supplement to reduce the risk
smoites
somites = give rise to vertebrea
along the spin- segmental structure
= segmental vertebrea
Development of brain vesicles
Brain region develops earlier then the cortical region
forebrain, midbrain and hindbrain
Cortical folding
Cortical folding, or gyrification, coincides with several
important developmental processes = increase surface
area
Neurogenesis
Progenitor cells proliferate to become neuroblasts.
Cells divide with nucleus at ventricular surface
Symmetric division produces two more progenitor cells.
bipolar cell.
the nucleus moves away from the ventricular surface and it comes down as the cell strarts
dividing –> m-phase
Progenitor cells undergo cell division to produce
neurons
progenitor cell = stem cell can produce neurons and
the glial cells
Neuroblast
In vertebrates, a neuroblast or primitive nerve cell is a postmitotic cell that does not divide further, and which will develop into a neuron after a migration phase.
no quite neuron yet
How do the neurons get to the cortex?
The neuroblasts generated from apical progenitor cells migrate along the process of the apical
progenitor cell to the cortex.
• This is radial migration
