The Cerebral Cortex is subdivided into different functional areas as follows:
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The somatosensory area, located behind the central fissure, receives impulses from the skin surface as well as from beneath the skin and, therefore, possesses sensations such as touch and taste. In front of the central fissure is the somatomotor area which is responsible for voluntary movement of body muscles.
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The area of the cortex concerned with hearing is the auditory area, which is in the upper part of the temporal lobe, the area for seeing, the visual cortex, is in the back portion, or occipital lobe, and the area governing our sense of smell, the olfactory area, is in the front portion of the temporal lobe. The area for language and speech, known as Broca’s Area, is responsible for the muscle movements of the throat and mouth used in speaking. Distinct from this is the area responsible for our understanding of speech and reading, which is between the auditory and visual areas.
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Communication in the brain takes the form of electrical impulses which run along pathways connecting the various sectors. These connections are formed by a group of dendroids which are threadlike extensions that grow out of neurons, the specialised cells of the nervous system. As well as dendroids, neurons have extensions called axons. Dendrites bring information to the cell body and axons take information away from the cell body.
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Each neuron is a cell that uses biochemical reactions to receive, process and transmit information, or messages, through an electrochemical process.
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The branches of a neuron’s dendrite (the dendritic tree) is connected to a thousand neighbouring neurons. It is when one of these neurons fire that a positive or negative charge is received by one of the dendrites. The strengths of all the charges are added together and the aggregate input is then passed to the soma, the cell body. The primary function of the soma and its nucleus is not in the processing of incoming and outgoing data but is to perform the continuous maintenance required to keep the neuron functional. It is just one part of the soma, the axon hillock, that concerns itself with the signal If the aggregate input is greater than the axon hillock’s threshold, this causes the neuron to fire and an output signal is transmitted down the axon.
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Neurons are the oldest and longest cells in the body and we have many of the same neurons for our whole life. Although other cells die and are replaced, many neurons are never replaced when they die, therefore, we have fewer neurons when we are old compared to when we are young. On the other hand data published in the late 1990s shows that in at least one area, the hippocampus, new neurons can grow in adult humans.
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The more connections there are among the brain’s hundred billion neurons, the more efficiently it will work. Connections form as a result of two elements; inherited growth patterns, and in response to external and internal stimuli.
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