NC150S05

NC150S05馥榕

Ch5 summary

The neuron is the fundamental unit of the nervous system. Its major characteristic is the ability to communicate within the nervous system, with other parts of the body, and with the environment. With billions of multisynaptic connections, the nerve cells serve higher mental functions that include memory, thinking, reasoning, calculation, and language. Neuroglial cells, which support and protect nerve cells, are important in tissue repair and participate in phagocytizing cellular debris. Nerve cells communicate with one another through nerve impulses that represent all neuronal activity. The nerve impulses have a chemical component that underlies the electric potential of the cells. A neurotransmitter is a chemical substance release at a synapse that transmits signals across neurons. There are two types of transmitters in the nervous system: small molecules and large molecules (peptides). Small-molecules neurotransmitters include acetylcholine, dopamine, norepinephrine, serotonin, glutamate, and GABA. They are known to have short-lasting effects. Large-molecule peptides produce long-lasting effects on postsynaptic nerve cells.

神經元是神經系統的基本單位，其主要的特色為具有溝通神經系統內部、及溝通身體其餘部分與環境間的能力。由於大量的多重突觸連結，使得神經細胞具有高等的心智功能，包含記憶、思考、推理、計算及語言。支撐及保護神經細胞的神經膠細胞，對於組織的修補及參與細胞殘骸的吞噬作用是相當重要的。神經細胞藉由代表所有神經性活動的神經脈衝來聯絡彼此。神經脈衝具有構成細胞電位基礎的化學組成，而神經傳導素是於突觸所被釋放的化學性物質，用來傳遞神經元間的訊號。神經系統中具有下列兩種傳導物質：小分子與大分子(胜肽)。小分子神經傳導物包含乙醯膽鹼、多巴胺、正腎上腺素、血清素、榖氨酸鹽及伽馬氨基丁酸。這些都具有短期的效用。而大分子胜肽在後突觸神經細胞可產生較長期的效用。