5 questions Essay Example | Topics and Well Written Essays - 1000 words - 2

5 questions - Essay Example Next to cell migration is cell differentiation that begins with gene expression, wherein previously dormant genes undergo activation, and which ends up with the cell producing a certain protein. Neuroblasts, at this point, turn into particular types of neurons. After cell differentiation is cell maturation, which happens 20 weeks after conception and continues after birth. It takes place through dendritic and axonal growth. Maturing neurons build dendrites to give surface area for synapses with other cells and to expand their axons to proper targets, which will launch synapse formation. Axonal growth relies on a particular process, which begins with the growth cone at the end of the axon. As these growth cones branch out, they create shoots or filopodia that, after they reach certain targets, other filopodia follow them. Next to cell maturation is synaptogenesis, or the creation of synaptic connections. Synapses reach 1014 or 100,000 trillion. After synaptogenesis is cell death and synaptic pruning. The brain chisels out unneeded neurons and prunes synapses. Neural Darwinism explains that the brain removes excess neurons through competition among them. Neurons die because target cells create neurotrophic factors that axon terminals absorb and which create messages that seem to tell some neurons to die in a programmed process called apoptosis. The last stage of brain development is myelogenesis or production of myelin. Myelination demonstrates cerebral maturation. Light energy travels through the pupil and into the light-sensitive surface of the eye called the retina. This activates the photoreceptor cells on the retina, which results to the creation of people’s visual worlds. The photoreceptor cells and neurons generate visual precision and enable people to see different colors, including dimness and brightness. Photoreceptors change light energy to chemical energy, which activates neural