up: [[Evolution of Development]] Tags: # How the brain grows throughout development #### Through what main process does the brain develop? The major concept of evolutionary brain development is that the genome is not elaborate enough to encode exactly how the brain will develop. Instead, **the connections in the brain are changed largely through experience. This is known as [[Experience plasticity]]. Interaction with the environment can also change genotype expression, which in turn changes phenotype (see: [[Experience can cause expression change in genotype which causes change in phenotype]]). ** ### How does the anatomy of the human brain develop in the womb? 1 ![[Pasted image 20221014073046.png]] The brain is built around a tube. During development, the front end of the brain adds many more cells than the back end. At first, it grows only laterally. Then it starts to grow upward, to the side, downward, forward, and backward. The part that expands backward will engulf the midbrain and parts of the hind brain. To form the cortex, layers one through six are constructed like a ladder. Layers one are built first, and then other neurons form on top of them. ### What are the six stages of neuronal development? 1 1. Neurogenesis: nonneuronal cells mitotically divide to become neuronal cells 2. Cell migration: movement of cells to establish distinct neuron populations 3. Cell differentiation: differentiation of precursor cells into distinctive types of neurons and glial cells 4. Synaptogenesis: the establishment of synoptical connections as axons and dendrites grow 5. Neuronal cell death: the selective death of many nerve cells 6. Synapse rearrangement: the loss of some synapses and creation of others ![[Pasted image 20220925082645.png]] Newton Masterfully Dodges Slippery Didgeridoos Slithering ![[Pasted image 20220925082942.png]] ### What is the trend in early brain development concerning amount of synapses and neurons created? 3 The overall trend of brain development is the brain vastly over-produces neurons in neurogenesis and synapses in a process called synaptogenesis at the beginning of development (first couple of years) and then prunes them much more later on in development. By the time you are born you have grown most of the neurons you will ever have. Because of this the brain has incredible [[Neuroplasticity]] during early stages of development. ### How does synaptogenesis occur on a cellular level? 1 Growth cones form on the tips of axons and dendrites alike and are pulled toward target cells by filopedia that adhere to cell adhesion molecules (CAMs). ![[Pasted image 20220925083927.png]] ##### Through what two processes do nerve cells degenerate? 1 ==Retrograde== regeneration occurs when nerve cells are injured near the cell body. It causes eventual cell atrophy. ==Anterograde== degeneration happens when nerve damage happens near the end of the axon. Usually it can repair itself. #### What determines what is pruned? 3 Active synapses are kept, whereas inactive synapses are pruned. ###### What do neurotrophic factors do? 2 If neuron cells receive ==neurotrophic== factors, they will be vastly less likely to die because they feed the neurons to help them survive. ###### How do neurons kill themselves through apoptosis? 1 Many neurons kill themselves through [[Apoptosis]]. This occurs by ==Diablo== protein released from the ==mitochondria== which blocks inhibitors of cell death and allows for caspases, families of proteins that cut up nucleases and DNA to release. ### What is the sensitive period? The sensory period is the period during which synaptogenesis is particularly prevalent and stimulation of neurons will affect the rest of the organism's life. ###### What is monocular deprivation and one eye deviation? Monocular deprivation is inability to see in one eye. It's caused if during the sensory period an animal is deprived of vision in both eyes or one eye for a few weeks, they will not be able to see when those eyes are opened; the neurons in the visual cortex for that eye were never stimulated and got pruned. ^29aba6 ![[Pasted image 20220923101354.png]] ### The brain still can change in adulthood [[Plasticity in sensory systems lasts into adulthood]] Related: Created: [[19-09-2022]]