神经元与神经胶质细胞优秀课件

Dendrite
• The part of the soma that does concern itself with the signal is the axon hillock. If the aggregate input is greater than the axon hillock's threshold value, then the neuron fires, and an output signal is transmitted down the axon. The strength of the output is constant, regardless of whether the input was just above the threshold, or a hundred times as great. The output strength is unaffected by the many divisions in the axon; it reaches each terminal button with the same intensity it had at the axon hillock. This uniformity is critical in an analogue device such as a brain where small errors can snowball, and where error correction is more difficult than in a digital system
细胞膜
细胞质
特征性结构： 1. 尼氏体：光镜下为嗜碱性小块或小颗粒，分布
与整个胞体和树突，轴突和轴丘中没有；电镜 下由粗面内质网、游离核糖体和多核糖体所构 成； 2. 神经原纤维，存在与胞体与突起中，电镜下相 当于微管、神经丝和微丝； 3. 线粒体特征：嵴纵向排列，线粒体内膜所围成 的腔室，其致密颗粒不常出现或缺如。
线粒体
为细胞活动提供能量 胞内钙的调节因素
Biblioteka Baidu
细胞核
形态 核膜
• 轴突 • 树突
神经元突起
Dendrite
• A neuron’s dendritic tree is connected to a thousand neighbouring neurons. When one of those neurons fire, a positive or negative charge is received by one of the dendrites. The strengths of all the received charges are added together through the processes of spatial and temporal summation. Spatial summation occurs when several weak signals are converted into a single large one, while temporal summation converts a rapid series of weak pulses from one source into one large signal .
树突
树突内的结构与核周质基本相似， 微管是树突最明显的细胞器 树突侧棘，是神经元之间形成突触的主要部位，功能尚不清 在大脑皮质锥体细胞和小脑皮质蒲肯野细胞的树突上，树突棘 数量最多而明显，一个蒲肯野细胞的树突棘可多达10万个以上。 树突的功能主要是接受刺激，树突棘和树突使神经元的接受面 大为扩大。
神经元与神经胶质 细胞
神经元的一般结构－－细胞体
神经元的细胞体
• 细胞膜
脂质双层，镶嵌蛋白
• 细胞质
尼氏体，神经原纤维，内质网，
高尔基复合体，溶酶体，多泡体，线粒体，
中心粒和纤毛，色素颗粒和脂褐素
• 细胞核
细胞膜
液态的脂质双层中镶嵌着球形蛋白
骨架是磷脂双分子层。 蛋白质分子以附着、镶嵌、贯穿的形式存在于磷脂双分子层上
Dendrites
• The treelike extensions of a neuron. Most neurons have multiple dendrites, which are short and typically highly branched. Dendrites are specialised for receiving information and form synaptic contacts with the terminals of other nerve cells to allow nerve impulses to be transmitted.
神经元胞体光镜结构，示尼氏体
细胞质
核糖体： 强噬碱性 游离型，主要合成结构蛋白 结合型，参与酶的合成 单个存在时无活性，只有当mRNA 将它串连起来并形成多核 蛋白体时才具有合成蛋白质的能力。
细胞质
高尔基器：存在于细胞核和树突近端。由几层扁平囊泡、 大泡所构成。小泡由光面内质网出芽更新而来，并携带 有粗面内质网合成的多肽和蛋白质等，故又称转移小泡。 通过扁平囊泡的加工浓缩，然后脱落成大泡。 可能参与突触小泡的形成和合成多肽激素的神经分泌颗 粒； 还可形成溶酶体
树突
一、树突 树突棘(spine) 分为细长型或鼓槌型 (drum,stick shape)，牙型(stubby shape）， 蘑菇型(mushroom shape)。
二、是突触后膜所在部位，也是外来冲动传 入部位。
Function of spines
• Dendritic spines are the contact sites for most excitatory synapses in the brain where they occur in vast numbers, estimated to be on the order of 1014 for the human cerebral cortex. Spines are particularly associated with neurons where inputs from diverse sources converge, such as pyramidal cells in the cerebral cortex, whose dendrites commonly have several thousand spines, each representing an excitatory synapse.