CNS(中枢神经系统)课件

1、Nervous system1Department of AnatomyLuzhou Medical College Edited by professor Xiao Nervous system Introduction The nervous system is composed of two parts, the central nervous system and peripheral nervous system. The former is represented by the brain and spinal cord; while the latter consists of

2、the spinal and cranial nerves. The autonomic nervous system, often considered as a separate functional entity, is a part central and a part peripheral. BrainSpinal cordCranial nervesSpinal nervesNervous system as a wholeThe nervous system possesses particular importance in all organs and systems of

3、human body. It modulates the different cells, tissues and organs, to complete certain activities or response exterior stimulus for the benefit of organism as a whole. The brain is commonly regarded as the organ solely concerned with thought, memory and consciousness. All information we have concerni

4、ngthe world about us is conveyed centrally to the brain by an elaborate sensory system. Nervous system IntroductionReceptor of many kinds act as transducers which change physical and chemical stimuli in our environment into nerve impulse which the brain can read and give meaning to. Attention, consc

5、iousness, emotional experience and sleep are all central neural functions. Such higher functions as memory, imagination(想像力), thought and creative ability are poorly understood（难懂的） but must be related to complex neuronal activity. While the gross features of the human brain are not especially impre

6、ssive（印象）, its versatility（多功能性）, potential capabilities（濽能）, efficiency（效率）and self-programming nature（自我谋略天性） put it in a class beyond any “electronic brain”.Nervous system IntroductionThe elements of the nervous systemThe nervous system composed of nervous tissue that consists of billions of nerv

7、e cells (neurons) and supported by a special variety of connective tissue known as neuroglia.The neuronThe neuron are independent structural unit of the nervous system and are functional specialized for reception, integration（整合）, and transmission of coded information（编码）.Nervous system Introduction

8、Each neuron possesses a nucleated cell body and two types of processes, an neuron, which conducts impulse away from the cell body, and one or more dendrites that conducts impulses towards the cell body. Both of these processes show marked morphological difference. The cell body serves as metabolic c

9、enter of the entire unit and consists of a large, pale nucleus and cytoplasm ( perikaryon). Nervous system IntroductionThe structures of the neuronThe nuclear envelope is double-layered membrane with numerous pores（小孔）. The chromatin（染色质） consists mostly of large molecules of deoxyribonucleic acid (

10、DNA). The nucleolus（核仁） occupies a prominent position in the nucleus, which is rich in ribonucleic acid (RNA). As in all cells, the nucleus engages in marked degree of protein synthesis. The organelles（细胞器） contained within the cytoplasm are common to other cells in the body, but there is abundant g

11、ranular endoplasmic reticulum that constitutes the Nissl body, a protein synthesis apparatus. Nervous system Introductionengage in 从事于The structures of the neuronThe axon is a slender process. It may arise from the conical region of the cell body called axon hillock, or from the base of one of the m

12、ain dendrites. The axon gives rise to several side branches or collaterals, usually oriented perpendicular（垂直的） to the main axon process. Distally, the axon breaks up into fine branches that end in swollen button called button terminal or axon terminal. The latter comes into contact with other neuro

13、ns to form synapse, or with muscle to cause muscle contraction, or with the gland to cause secretion. The plasmic membrane of the axon is known as axolemma（轴膜） and the interior of axon called axoplasm（轴索原浆）. The axoplasm differs from the cytoplasm of the dendrites by complete absence of the Nissl bo

14、dy. Components of the axoplasm consist of agranular endoplasmic reticulum, mitochondria, microtubules and neurofilments. The terminal segments of axon comprises numerous synaptic vesicles that contain neurotransmitter substances.Nervous system IntroductionThe structures of the neuron Because the axo

15、plasm does not contain RNA, proteins synthesis cannot take place in the axon. All axonal proteins, therefore, must come from the cell body, and products are transported by a perpetual（永久的） axoplasmic motion, some organelles, structural protein and neurotransmitters contained within cytoplasm are car

16、ried by axoplasmic flow which moves in both directions and with varying velocity. The anterograde transport, moving from the cell body to the nerve terminals, has two types of rate: one is the slow transport, which is bulk flow（总体流动） of axoplasm carrying mitochondria, lysosomes（溶酶体） and vesicles; th

17、e other is a rapid transport which moves the membrane-bound vesicles, and other material.Nervous system IntroductionAxoplasmic transportThe retrograde transports, moving from the synaptic terminal to the cell body, provide a feedback passage. Some pinocytotic（胞饮的） material uptaken by an axonal termi

18、nals or distal dendrites are carried to the cell body for utilization or lysosomal degradation. The axoplasmic transport can be used experimentally to determine neuronal connectivity（连通性） by an axon-tracing technique and gas a clinic implication as centripetal（向心力） transport of neurotoxic（神经毒素） and

19、infective agents, which may be responsible for some disease.Nervous system IntroductionAxoplasmic transportNervous system IntroductionClassification of the neuronneuronBipolar neuron pseudounipolar neuronMultipolar neuronAccording to the numberOf their processesneuronSensory neuronMotor neuron Assoc

20、iation neuronAfferent neuronEfferent neuronIntermediate neuronfunctionallyneuronSmall Medium Large From 10200umBipolar neuronpseudounipolar neuronMultipolar neurondendritenucleusaxonNissl bodyAxon hillockNervous system IntroductionSynapses concept of the synapseWithin the nervous system impulses are

21、 conducted fromOne part to another along a chain of neurons. The terminal arborizations of the axon of one neuron ramify in closecontact with the cell body or dentrites, less frequently with axonic terminals of many others.Concept Of the synapsesStructures of the synapsesEach synapse involves the cl

22、ose apposition of a presynaptic element with a postSynaptic element from which it is separated by a synaptic cleft. The presynaptic element contains numerous synaptic vesicles in which the chemical substance neurotransmitter is present. ()Presynaptic membranePostsynapse membraneSynaptic cleftSynapti

23、c vesicleMitochondria Nervous system IntroductionSynapses ()When an impulse arrives at the presynaptic element, the neurotransmitter Diffuses across the synaptic cleft and binds to receptor molecules in the postsynaptic membrane. As a result, the postsynaptic neuron is activated and impulse is condu

24、cted from one neuron to the others. The “chemical synapse” involving the release the transmitter substance is the most common type in the mammalian nervous system. The axon of lower motor neuron project through peripheral nerves to Muscle cells and terminate at a specialized portion of the muscle me

25、mbraneWhich are called neuromuscular junctions or motor end plates. The fibersInnervating the voluntary muscles of the body and limbs are the axon of large multipolar nerve cells located in anterior horn of the gray matter of The spinal cord. It has been estimated that each of these motor neuronsRec

26、eives synaptic connections from the terminal axonal ramifications of Up to 1000 other nerve cells. Nervous system Introduction.The neurogliaNeuroglia cells outnumber neurons in the central nervous system10:1. These cells appear to play a number of important roles, including myelin formation, guidanc

27、e of developing neurons, maintenace of extracellular K+levels, and reuptake of transmitters after synaptic activity.The astrocytes Astrocytes have many radiating processes, some of which end at Nerve cells and others at capillaries. They are neuroectodermal inOrigin and may assist in the transfer of

28、 nutrients and metabolic Products between the neurons and the blood. Nervous system Introduction2. The oligodendrocytesOligodendrocytes are smaller and have fewer branching processes; they tend to lay in rows between nerve fibers and are concerned with the production and nourishment of myelin sheath

29、s especially those surround axons in the central nervous system. They are neuroectodermal in origin.3. The microgliaMicroglia are diminutive cells, which permeate the entire central nervous system. They are modified macrophages and form partOf the reticulo-endothelial system and are probably mesoder

30、malIn origin.Nervous system Introduction. The reflex and reflex arcReflexes are subconscious stimulus-esponse mechanism. The reflex arc, a linkage of afferent and efferent neurons, is defined as the entire neural pathway that is involved in a reflex. Several structures are involved in the reflex arc

31、. These include the receptor whose stimulation initiates an impulse; the afferent neuron, which transmits the impulse through a peripheral nerve to the central nervous systemNervous system Introduction Terminology Gray matterIn the CNS, the part of aggregations of nerve cell bodiesEmbedded in a netw

32、ork of delicate nerve processes is Known as gray matter, it has a gray color during the Fresh condition.Cortex The cortex is the outmost layer of gray matter in the Cerebral hemispheres or in the cerebellum. The cellBodies in the cortex are arranged in more or less well-Defined laminae or layers.Nucleus Nerve cells with common shape, function and connectionswithin the CNS are grouped together into nucleus.Ganglion Nerve cells with the same s