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These "homunculus" diagrams are based on experimental recordings of anesthetized subjects. The "motor homunculus" was determined by electrical stimulation of locations in the primary motor cortex to see what muscles responded. Notice that the lips and fingers are over-represented, indicating fine motor control of those structures. The "sensory homunculus" was determined by gently stroking parts of the body surface to see what locations in the primary somatosensory cortex responded electrically. Notice that the face and hands, which are very sensitive, are over-represented, while the body trunk is relatively insensitive. |
Autonomic nervous system
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Serotonin levels replenished during sleep. Abnormal levels of Neurotransmitters in the brain may cause mental illness: Insufficient dopamine--- Parkinsonism Too much dopamine--- schizophrenia Evidence: high drug doses Insufficient serotonin--- depression; suicide |