tailieunhanh - DEVELOPMENTAL NEUROBIOLOGY - PART 10

Lý thuyết rằng tinh thể nhánh cây thay đổi hình dạng và xếp lại hoặc mở rộng đáp ứng nhu cầu chức năng được tổ chức vào cuối thế kỷ 19. Các lý thuyết về chuyển động ameboid của các tinh thể nhánh cây đã được đề xuất bởi Rabl-Rückhard (1890) và Duval (1895). Lúc đầu Cajal (1895) ủng hộ lý thuyết | Beginnings of the Nervous System Chapter 14 387 and curari sic and is not identical with the substance which contracts. This theory was included in a research program that had started with the simultaneous discovery by Claude Bernard and Albert Koelliker about 1844 that curare blocks transmission at the neuromuscular junction Bernard 1878 pp. 237-315 and it culminated in purification of the nicotinic actylcholine receptor its molecular cloning and elucidation of its primary structure reviewed by Changeux et al. 1984 Schuetze and Role 1987 . The theory that dendrites change shape and retract or extend in response to functional demands was widely held at the end of the 19th century. The theory of ameboid movements of the dendrites was proposed by Rabl-Ruckhard 1890 and Duval 1895 . At first Cajal 1895 supported the theory and added to it the possibility that neuroglial cells penetrate into the space left by retraction of dendrites during sleep or anesthesia. Later Cajal 1909-1911 argued that the theory was unsupported by any evidence showing the required anatomical changes at synapses but as we know lack of evidence is not a good reason for abandoning a theory for that there must be well-corroborated counterevidence. Some counterevidence was obtained by Sherrington 1906 p. 24 who pointed out that the reflex delay latent period is longer on the second occasion when a reflex is produced in two stages than when a single full-strength reflex is produced This argues against an amoeboid movement of the protoplasm of the cell being the step which determines its conductive communication with the next. That was a fine argument at the time but subsequent research has shown changes in synaptic size and shape as a result of stimulation Sotelo and Palay 1971 Baily and Chen 1983 1988 Wernig and Herrara 1986 and the molecular mechanism for rapid changes in size and shape of dendritic spines has been discovered Coss 1985 Filkova 1985a b . We should now consider the theory that .