8.1 神经细胞
章节大纲
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The nerve send electrical "sparks" that transmit signals throughout your body.
::神经发出电源“电源” 将信号传送到全身Nerve Cells
::神经细胞Introduction to the Nervous System
::神经系统介绍Your body has two systems that help you maintain : the and the . The nervous system is a complex network of nervous tissue that transmits electrical and chemical signals. The nervous system consists of the (CNS) and the (PNS). The central nervous system is made up of the brain and spinal cord , while the peripheral nervous system is made up of the nervous tissue that lies outside the CNS such as the nerves in the legs, arms, hands, feet, and organs of the body. The nervous system mediates between different parts of the body as well as the body’s interactions with the environment.
::神经系统是由神经组织组成的复杂的神经组织网络,可以传输电气和化学信号。神经系统由(CNS)和(PNS)组成。 中枢神经系统由大脑和脊髓组成,而外围神经系统则由CNS以外的神经组织组成,如腿部、手臂、手部、脚部和身体器官中的神经组织。神经系统在身体的不同部分之间以及身体与环境的相互作用之间进行调节。The endocrine system is the system of glands throughout the body that releases chemical signal molecules into the bloodstream. The electrical signals of the nervous system move very rapidly along nervous tissue, while the chemical signals of the endocrine system act slowly in comparison and over a longer period of time. Working together, the nervous and endocrine systems allow your body to respond to short or long term changes in your environment such as a pedestrian suddenly stepping out in front of your bike or your body adapting to cycling in a warm, humid summer evening, as shown in Figure .
::内分泌系统是将化学信号分子释放到血液中的全身腺系统,神经系统的电子信号在神经组织中移动非常迅速,而内分泌系统的化学信号相对缓慢,在较长的一段时间内发挥作用,同时,神经和内分泌系统使你的身体能够应对环境的短期或长期变化,例如行人突然走出自行车前或身体,在温暖、潮湿的夏季夜晚适应自行车,如图所示。Cycling home in rush-hour traffic demands a lot of your nervous and endocrine systems. Your nervous system—mostly through your eyes and ears—constantly monitors your surroundings, alerting you instantly at any sign of change or danger. Your endocrine system gears up your muscles and cardiovascular system for the ride by flooding your body with metabolism-boosting hormones.
::你的神经系统 — — 主要是通过你的眼睛和耳朵 — — 持续地监视周围环境,当任何变化或危险迹象出现时立即提醒你。 你的内分泌系统将肌肉和心血管系统安装起来,以便用新陈代谢刺激荷尔蒙充斥身体。Neurons
::中中Although the nervous system is very complex, there are only two main types of nerve cells in nervous tissue. All parts of the nervous system are made of nervous tissue. The neuron is the "conducting" cell that transmits electrical signals, and it is the structural unit of the nervous system. The other cells, glial cells , provide a support system for the neurons, and recent research has discovered they are involved in formation. A type of glial cell in the brain, called an astrocyte, is important for the maturation of neurons and may be involved in repairing damaged nervous tissue. Neurons and glial cells make up most of the brain, the spinal cord, and the nerves that branch out to every part of the body. Neurons and glial cells are both considered nerve cells.
::尽管神经系统非常复杂,但神经组织中只有两大类神经细胞。神经系统的各个部分都是由神经组织组成的。神经系统是由神经组织组成的“导体”细胞,是传输电子信号的神经系统的结构单元。其他细胞,即滑翔细胞,为神经系统提供了支持系统,最近的研究发现它们正在形成。大脑中有一种叫“天体细胞”的滑翔细胞,对于神经系统的成熟很重要,并且可能参与修复受损的神经组织。神经和滑翔细胞构成大部分大脑、脊髓和向身体每个部位延伸的神经。神经和滑翔细胞都被视为神经细胞。Structure of a Neuron
::中中结构结构The special shape of a neuron allows it to pass an electrical signal to another neuron and to other cells. Electrical signals move rapidly along neurons so that they can quickly pass “messages” from one part of the body to another. These electrical signals are called .
::神经元的特殊形状允许它将电子信号传递给另一个神经元和其他细胞。 电子信号在神经元上迅速移动,以便它们能够从身体的一个部位迅速传递“信息 ” 。 这些电子信号被称为 : “ 电子信号 ” 。Neurons are typically made up of a cell body (or soma), dendrites , and an axon , as shown in Figure . The soma contains the and other , much like the structures in other . The dendrites extend from the cell body and receive nerve impulses from other cells. The soma collects information from the dendrites and passes it along to the axon. The axon is a long membrane-bound extension of the cell body that passes the nerve impulse to the next cell. The end of the axon is called the axon terminal . The axon terminal is the point at which the neuron communicates with the next cell. The axons of many neurons are covered with an electrically insulating phospholipid layer called a myelin sheath . The myelin speeds up the transmission of nerve impulses along the axon. It acts as a layer of insulation, like the plastic you would see around an electrical cord.
::神经通常是由细胞体(或索马)、 dendrites 和 axon 组成,如图所示。 索马包含细胞体和其他结构, 类似于其他细胞的结构。 解剖从细胞体中延伸, 并接收其他细胞的神经脉冲。 索马收集了来自 dendrite 的信息, 并将信息传送到轴。 轴是细胞体的长膜延伸, 将神经脉冲传递到下一个细胞中。 轴的末端被称为轴终端。 轴终端是神经与下一个细胞沟通的点。 许多神经的轴被一个电绝缘性磷素层覆盖, 叫做 myelin Sheath。 粒子将神经脉冲传送到轴中。 它像电线条周围的塑料一样, 其作用为一层隔热层。The general structure of a neuron. Neurons come in many different shapes and sizes, but they all have a cell body, dendrites, and an axon. The cell body contains a nucleus and other organelles. However, not all neurons have a myelin sheath.
::神经元的一般结构。 神经元的形状和大小各不相同, 但它们都有一个细胞体、 外形和轴。 细胞体包含一个核和其他有机体。 但是, 并非所有神经元都有一个甲状腺。The myelin is an outgrowth of glial cells. Schwann cells, which are shown wrapped around the neuron in Figure , are a type of glial cell. Schwann cells are flat and thin and, like other cells, contain a nucleus and other organelles. Schwann cells supply the myelin for neurons that are not part of the brain or spinal cord, while another type of glial cell, called oligodendrocytes, supply myelin to those of the brain and spinal cord. Myelinated neurons are white in appearance, and they are what makes up the "white matter" of the brain. Myelin is not continuous along the axon; there are regular gaps in the myelin sheath called nodes of Ranvier. At each node, there are ion channels ; these are the only points at which ions can move across the axon membrane. In this way, the nodes act to strengthen nerve impulses by concentrating the flow of ions.
::闪光是滑翔细胞的产物。Schwann细胞在图中围绕神经细胞的四周显示,是某种闪光细胞。Schwann细胞是平的和薄的,与其他细胞一样,含有核和其他器官。Schwann细胞为不属于大脑或脊髓的神经元提供闪光素,而另一种称为寡头细胞的闪光细胞,为大脑和脊髓的细胞提供闪光素。在图中,被割除的神经元是白色的,它们构成大脑的“白色物质”。Myelin在轴上不是连续的;在叫作Ranvier节点的 myelin Sheath 中经常有缝隙。在每个节点,都有电离子通道;这是离子能够跨过轴膜的唯一点。在这种方式下,结点通过集中离子的流来增强神经脉冲。A transmission electron microscope (TEM) image of a cross section of a myelinated axon. The “rings” around the axon are made up of Schwann cell membrane, which is wrapped many times around the axon.
::轴周围的“环”由Schwann细胞膜组成,环绕轴部多次。Neurons are specialized cells designed for the efficient passing of cell signals. Given the many functions carried out by neurons in different parts of the nervous system, there are many different shapes and sizes of neurons. For example, the cell body of a neuron can vary from four to one hundred micrometers in diameter. Some neurons have over one thousand dendrite branches and make connections with tens of thousands of cells. Other neurons have only one or two dendrites, each of which has thousands of synapses. A synapse, or synaptic cleft , is the small gap between the dendrite of one neuron and the axon of another. It is through this gap, shown in Figure , that neurons pass electrical signals across the nervous system.
::神经元是专门为有效传递细胞信号而设计的专门细胞。考虑到神经系统不同部分神经元所执行的许多功能,神经元的形状和大小各有不同。例如,神经元的细胞体直径可以从4微米到100微米不等。有些神经元有1 000多个脱衣树枝,与数万个细胞相连接。其他神经元只有一个或两个脱衣树,每个神经元都有数千个突触。一个神经元的突触,或突触裂,是一个神经元的外形和另一个神经元的轴之间的小差距。正是通过图所示的这一差距,神经元在整个神经系统传递了电子信号。Similarly, neurons may have one or many axons. The longest axon of a human motor neuron can be over a meter long, reaching from the base of the spine to the toes. Sensory neurons have axons that run from the toes to the spinal cord, over 1.5 meters in adults. Giraffes have single axons, which are several meters in length, running along the entire length of their necks.
::类似地,神经元可能有一个或多个轴。人类运动神经元最长的轴长一米以上,从脊椎底部到脚趾。感官神经元有从脚趾到脊髓的斧子,在成人中超过1.5米。长几米的螺旋有一个轴,贯穿整个颈部。As shown in this depiction of a detailed neuron, synapses are found at the end of the axons (called axon terminals) and help connect a single neuron to thousands of other neurons. Chemical messages called neurotransmitters are released at the synapses and pass the “message” onto the next neuron or other type of cell.
::正如对详细神经元的描述所示,突触出现在斧子(所谓的轴终端)的末尾,帮助连接单一神经元和其他数千个神经元。 被称为神经传送器的化学信息会在突触中释放出来,并将“信息”传递给下一个神经元或其他类型的细胞。Summary
::摘要-
The nervous system is composed of the central nervous system and the peripheral nervous system.
::神经系统由中枢神经系统和外围神经系统组成。 -
Neurons and glial cells are the two types of cells in the nervous system.
::神经系统中的两种细胞是中微细胞和中微细胞。 -
Electrical impulses pass information through the nervous system, from the axon of one neuron, across the synapse, and into the dendrite of the next neuron.
::电脉冲传递信息 通过神经系统, 从一个神经元的轴轴, 穿过突触, 并传递到下一个神经元的印记。
Review
::回顾-
What types of cells make up the nervous system?
::神经系统是由何种细胞构成的? -
Draw and label a neuron.
::绘制并标注神经元。 -
What is the difference between the central and peripheral nervous systems?
::中央和外围神经系统有什么区别?
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The nervous system is composed of the central nervous system and the peripheral nervous system.
