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					Neurobiology
Jiping Zhang (张季平)
Ph.D in Physiology Professor of Neurobiology School of Life Science East China Normal University Email: jpzhang@bio.ecnu.edu.cn Tel: 62232775/62238589

About this course
• • • • Bi-lingual course (60% English, 40% Chinese) 3 credits Reading materials References
NEUROSCIENCE, by Dale Purves et al, second edition NEUROBIOLOGY, Molecules, Cells and Systems, second edition, by Gary Matthews 华东师范大学神经生物学双语课程网 http://jpkc.ecnu.edu.cn/sy0702/index.htm
《神经生物学 》 主编 鞠躬 副主编 吕国蔚 王百忍 人民卫生出版社 《神经生物学 》 主编 寿天德主编 高等教育出版社

About this course
Examination Final Score 1. Attendance 2. Performance in class 3. English presentation 4. Final exam

10% 10% 20% 60%

About this course
Objective of this course 1. Get a good knowledge and understanding of the basic of Neurobiology 2. Setup your confidence to speak English in public place 3. Improve your ability to communicate topics in neurobiology in English 4. Cultivate your scientific way of thinking

About this course
What knowledge can you get from this course? 1. An overview of the nervous system 2. Neural signaling 3. Sensory and sensory processing 4. Brain development and its plasticity 5. Complex brain functions

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Organization of the Nervous System
• Central Nervous System (中枢神经系统) - Brain and spinal cord ( 脑和脊髓) • Peripheral Nervous System (周围神经系统) - everything else! - cranial nerves (12) (脑神经) - spinal nerves (31) (脊神经)

Questions
• What are the basic unit of the nervous system? • What are the functions (功能) of the nervous system? • How do we describe(描述) the anatomy (解剖) and function of the nervous system?

Cells are the basic units of the nervous system

Debates about the basic unit of the nervous system
• Reticular theory (Camillo Golgi)
Each nerve cell was connected to its neighbors by protoplasmic (原生质)links, forming a continuous nerve cell network or reticulum (网状组织)

• Synapse theory (Santiago Ramon y Cajal)
Nervous system are made up of discrete (分离的) cells, and that nerve cells communicate with one another by means of specialized contacts that eventually came to be called “synapses(突触)"

Silver impregnation method (银 染法) to stain neurons
• Introduced by Italian pathologist Camillo Golgi (1852-1934) • Advantages: 1. Silver stains in a random manner, only about one percent of cells in any particular region of the brain, make it possible to study a single nerve cells in isolation (分离) 2. The neurons that do take up the stain are delineated (描绘) in their entire extent, including the cell body, axon, and full dendritic tree.

The Nobel Prize in Physiology or Medicine 1906
"in recognition of their work on the structure of the nervous system"

Camillo Golgi (1843-1926)

Santiago Ramon y Cajal ( 1852-1934)

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Structural diversity in the nervous system demonstrated with cellular and molecular markers
Nissl stain (尼式染色法) Golgi-labled cell (left two) (高尔基染色标记细胞) fluorescent dye labeled cell (荧光染色法) Cellular and molecular approaches to seeing neural connections and systems

The nervous system has two classes of cells
• Nerve cells (neurons,神经细胞或神经元)
For electrical signaling (电信号) 10 billions of neurons in the nervous system

• Glia cells (神经胶质细胞)
Not for electrical signaling 10 to 50 times more glia cells than neurons in nervous system Provide fitness and structure of the brain Separate and occasionally insulate (绝缘) groups of neurons from each other

Neurocytology Nerve cell
• Neurons - Cell body(细胞体) - Dendrites(树突) - Axon(轴突)

Axon
• The cell’s output structure • One axon per cell, 2 distinct parts
– tubelike structure --branches at end that connect to dendrites of other cells

Myelin sheath (髓鞘)
• White fatty casing on axon • Acts as an electrical insulator (绝缘体) • Not present on all cells • Increases the speed of neural signals down the axon.
Myelin Sheath

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Myelin sheath and Schwann cells

Dendrites
• Information collectors • Receive inputs from neighboring neurons • Inputs may number in thousands • If enough inputs the cell’s AXON may generate an output

Neuron structure
• cell body
– contains nucleus (核)& organelles (细胞器)

Nerve cell and its component parts
Synapse (突触)

• dendrite
– Conducts (传导) signals to cell body

• axon
– long fibers – specialized for electrical conduction

Myelinated axon 有髓鞘的轴突

Node of Ranvier 郎飞式结

Neurons and their dendrites
• Nerve cells that lack dendrites are usually innervated by just one or a few other nerve cells • Nerve cells that have elaborate dendrites are often innervated by a larger number of other neurons.

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Contacts between neurons

Structure of a vertebrate neuron

Some synapses form on the dendrites, cell body, or the axon hillock(轴丘)

Similarity between neurons and other cells
Neurons are surrounded by a cell membrane. Neurons have a nucleus that contains genes. Neurons contain cytoplasm(细胞质), mitochondria (线粒体) and other organelles. Neurons carry out basic cellular processes such as protein synthesis(合成) and energy production.

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Differences between neurons and other cells
1. Neurons have specialized extensions called dendrites and axons. Dendrites bring information to the cell body and axons take information away from the cell body. 2. Neurons communicate with each other through an electrochemical process. 3. Neurons contain some specialized structures (for example, synapses) and chemicals (for example, neurotransmitters).

The differences between axons and dendrites
Axons
•Take information away from the cell body •Smooth Surface •Generally only 1 axon per cell •No ribosomes(核糖体) •Can have myelin •Branch further from the cell body

Dendrites
•Bring information to the cell body •Rough Surface (dendritic spines) •Usually many dendrites per cell •Have ribosomes •No myelin insulation •Branch near the cell body

Classification of neurons by function
Sensory (or afferent) neurons(感觉神经元) They send information from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) TOWARD the central nervous system. Motor (or efferent) neurons(运动神经元) They send information AWAY from the central nervous system to muscles or glands. Interneurons(中间神经元) They send information between sensory neurons and motor neurons. Most interneurons are located in the central nervous system.

Classify neurons by the number of extensions that extend from the neuron's cell body
Pseudounipolar cells 假单极神经元) (example: dorsal root ganglion cells). Actually, these cells have 2 axons rather than an axon and dendrite. One axon extends centrally toward the spinal cord, the other axon extends toward the skin or muscle. Bipolar neurons (双极神经元) have two processes extending from the cell body (examples: retinal cells, olfactory epithelium cells).

Neuroglial cells

Multipolar neurons (多极神经元) have many processes that extend from the cell body. However, each neuron has only one axon (examples: spinal motor neurons, pyramidal neurons, Purkinje cells).

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Neuroglial cells

Glial Cells in the CNS
• Astrocytes (星型胶质细胞)
Maintain, in a variety of ways, an appropriate chemical environment for neuronal signaling

• Oligodendrocytes (少突细胞, in CNS) – myelin
Their Myelin has important effects on the speed of action potential conduction

• Microglia(小胶质细胞)
They are primarily scavenger(清道夫) cells that remove cellular debris from sites of injury or normal cell turnover

PNS Supporting Cells
• Schwaan cells: (施万(旺)细胞)
form myelin sheath around one axon 包绕于周围神经的周围,参与髓鞘的形成

Nodes of Ranvier(郎飞氏结)

Role of Glia
1. Act as a scaffolding(支架) for neuronal migration and axon outgrowth 2. Participate in the uptake and metabolism of the neurotransmitters (神经递质) that neurons use for intercellular communication. 3. Take up and buffer ions form the extracellular environment. 4. Act as scavengers(清道夫) to remove debris(残 骸) produced by dying neurons.

Unmyelinated(无髓鞘) areas of the axon located between adjacent Schwaan cells (or oligodendrocytes少突细胞)

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Role of Glia
5. Segregate groups of neurons from one another and act as electrical insulators between neurons. 6. Provide structural support of neurons. 7. Play a nurturing role, supplying metabolic components. 8. Play a role in information handling and memory storage.

Glial cells
Glial cells: - - Support neurons (physically, and nutrients营养) - - Cover neurons with myelin - - Clean up debris (残骸)

Myotatic reflex (牵张反射) neural circuits

Neural circuits

Recording neuronal responses
• Intracellular recording
– Sharp glass electrode or patch electrode – Typically in vitro离体

• Extracellular recordings primarily detect action potentials, the all-or-nothing changes in the potential across nerve cell membranes that convey information from one point to another in the nervous system. • Intracellular recordings can detect the smaller graded potential changes that serve to trigger action potentials. These graded triggering potentials can arise at either sensory receptors or synapses and are called receptor potentials or synaptic potentials, respectively

• Extracellular recording
– Typically in vivo在体

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Relative frequency of action potentials in different components of the myotatic reflex as the reflex pathway is activated

Intracellularly (细胞内) recorded responses underlying the myotatic reflex (牵张反射)

The major components of the nervous system and their functional relationships

Neural systems

Overview of vertebrate nervous system
Nervous systems perform three overlapping functions

Functions of the nervous system
Sensory Input • gather information from sensory receptors • analyze and interpret and route to CNS the gathered • conduct signals to information and come effector cells (e.g., (e.g., up with response muscles, glands) Motor Output Integration

• Receives information – Signals from sensory receptors • Integrates information – Assembles (装配) pieces into whole • Stimulates movement – Signals to muscles and glands • Maintains homeostasis (动态平衡) – Prevents change

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