CNS(中枢神经系统).ppt

The nervous system possesses particular importance in all organs and systems of human body. It modulates the different cells, tissues and organs, to complete certain activities or response exterior stimulus for the benefit of organism as a whole. The brain is commonly regarded as the organ solely concerned with thought, memory and consciousness. All information we have concerning the world about us is conveyed centrally to the brain by an elaborate sensory system. Receptor of many kinds act as transducers which change physical and chemical stimuli in our environment into nerve impulse which the brain can read and give meaning to. Attention, consciousness, emotional experience and sleep are all central neural functions. Such higher functions as memory, imagination(想像力), thought and creative ability are poorly understood（难懂的） but must be related to complex neuronal activity. While the gross features of the human brain are not especially impressive（印象）, its versatility（多功能性）, potential capabilities（濽能）, efficiency（效率）and self-programming nature（自我谋略天性） put it in a class beyond any “electronic brain”. The elements of the nervous system The nervous system composed of nervous tissue that consists of billions of nerve cells (neurons) and supported by a special variety of connective tissue known as neuroglia. The neuron The neuron are independent structural unit of the nervous system and are functional specialized for reception, integration（整合）, and transmission of coded information（编码）. Each neuron possesses a nucleated cell body and two types of processes, an neuron, which conducts impulse away from the cell body, and one or more dendrites that conducts impulses towards the cell body. Both of these processes show marked morphological difference. The cell body serves as metabolic center of the entire unit and consists of a large, pale nucleus and cytoplasm ( perikaryon). The nuclear envelope is double-layered membrane with numerous pores（小孔）. The chromatin（染色质） consi