Brain Development and Plasticity Flashcards
What is neurulation and when does it start?
Neuraliation begins after about 1 month of gestation. After the simple premordial fertilized egg differentiates into specific types of tissue (e.g., muscle, skeletal, cardiovascular, nerve), the spinal cord and brain are nothing more than a hollow tube. The information of this tube is referred to as neurulation. With time, the tube folds, tiwists, turns, and expands to become the fetal brain, while the hole inside the tube becomes the ventricular system.
What is neurogenesis and when does it start?
Around the seventh week of gestation, the nerve cells and glia near the inside of the tube divide, proliferate, and then begin to migrate outward. Neurogenesis, or the generation of new nerve cells, occurs in the area right around the ventricle. In this process, the tube acts much like a port around which the initial neural settlers will reside. As more neurons are generated, the central areas around the ventricle become settled, and then the new neurons, like new immigrants to a city, must traverse farther out to find a place to live. As the brain grows, new neurons travel farther and father out to the metaphorical suburbs of the brain. Glial cells provide the scaffolding or roads along which nerve cells can migrate to their ultimate destinations. Thus, the six layers of cortex are built from the inside out; the first set of cells migrates to the deepest layer of the cortex (the sixth), the second the fifth, and so forth. By six months of gestation, most neurons have been produced.
How does neurogenesis create new nerve cells?
The creation of new nerve cells in embryonic developmet occurs in the ventricular zone. Progenitor cells that line the ventricles can divide, producing new daughter cells. The daughter cells can either stay in the ventricular zone and act as new progenitor cells, or they can migrate away from this zone and into other areas of the brain.
What is synaptogenesis?
The formation of synapses between neurons in the nervous system. Although it occurs throughout a healthy person’s lifespan, an explosion of synapse formation occurs during early brain development. Dendrites in cortical regions increase greatly in number early in life, providing greater surface area for synaptic connections.
What are cadherins?
A family of molecules that help guide developing axons to synapse with certain targets and to adhere to those targets.
Where does synaptogenesis occur most rapidly?
In the primary sensory and motor areas first, followed by association areas and prefrontal cortex.
What happens after synapse proliferation?
Pruning occurs through the elimination of synapses, in which the number of connections between neurons is reduced.
Why does pruning happen?
In part because cells that do not receive so-called “survival factor” signals from their neighbouring cells undergp apoptosis, or programmed cell death. In other cases, the cells themselves do not die, but their synapses are disassembled and their axons retract or degenerate.
