CNS(中樞神經(jīng)系統(tǒng))

1、 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 the spinal and cranial nerves. The autonomic nervous syste

2、m, often considered as a separate functional entity, is a part central and a part peripheral. BrainSpinal cordCranial nervesSpinal nervesNervous system as a wholenThe nervous system possesses particular importance in all organs and systems of human body. It modulates the different cells, tissues and

3、 organs, to complete certain activities or response nexterior stimulus for the benefit of organism as a whole. nThe brain is commonly regarded as the organ solely concerned with thought, memory and consciousness. All information we have concerningnthe world about us is conveyed centrally to the brai

4、n by an elaborate sensory system. Nervous system IntroductionnReceptor 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, consciousness, emotional experience and sleep are all cent

5、ral neural functions. Such higher functions as memory, imagination(想像力), thought and creative ability are poorly understood（難懂的） but must be related to complex neuronal activity. While the gross features of the human brain are not especially impressive（印象）, its versatility（多功能性）, potential capabilit

6、ies（濽能）, efficiency（效率）and self-programming nature（自我謀略天性） put it in a class beyond any “electronic brain”.Nervous system Introduction整合）Nervous system IntroductionRough granularEndoplasmicreticulum Smooth granularEndoplasmic reticulumMicrotubuleSchwanns cellMyelin sheathNervous system IntroductionN

7、ervous system IntroductionNervous system IntroductionNervous system IntroductionNervous system IntroductionAxoplasmic transportNervous system IntroductionAxoplasmic transportNervous system IntroductionAxoplasmic transportNervous system IntroductionClassification of the neuronneuronBipolar neuron pse

8、udounipolar neuronMultipolar neuronAccording to the numberOf their processesneuronSensory neuronMotor neuron Association neuronAfferent neuronEfferent neuronIntermediate neuronfunctionallyneuronSmall Medium Large From 10200umBipolar neuronpseudounipolar neuronMultipolar neurondendritenucleusaxonNiss

9、l bodyAxon hillockNervous system Introduction nervous fibersThe longer processes of the neuron enveloped by themyelin sheath and the neurilemma are termed nerve fibers. The myelinated fibers are surrounded by a myelin sheath and neurilemma. The unmyelinated fibers are not, however, insulated（絕緣的） by

10、 a myelin sheath. Oligodendrocytes form myelin in the central nervoussystem while Schwann cells form myelin in peripheral nerves.Nervous system IntroductionSynapses concept of the synapseWithin the nervous system impulses are conducted fromOne part to another along a chain of neurons. The terminal a

11、rborizations 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 close apposition of a presynaptic element with a postSynaptic element from wh

12、ich 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 cleftSynaptic vesicleMitochondria Nervous system IntroductionSynapses ()When an impulse

13、 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 conducted from one neuron to the others. The “chemical synapse” involving the re

14、lease 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 membraneWhich are called neuromuscular junctions or motor end plates. The fib

15、ersInnervating 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 neuronsReceives synaptic connections from the terminal axonal ramifications of Up to

16、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, guidance of developing neurons, maintenace of extracellular K+levels, and reuptake

17、 of transmitters after synaptic activity.1.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 nutrients and metabolic Products between the neurons and the blood. Nerv

18、ous 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 sheaths especially those surround axons in the central nervous system. They are

19、 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 mesodermalIn origin.Nervous system Introduction. The reflex and reflex arcReflex

20、es 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. These include the receptor whose stimulation initiates an impulse; the

21、afferent neuron, which transmits the impulse through a peripheral nerve to the central nervous systemwhere the nerve synapses with a lower motor neuron or an interneuron up to one or more interneurons which relay the impulse to the efferent neurons; the efferent neuron which passes outward in the ne

22、rve and delivers the impulse to the effectorand an effector. The interruption of this reflex arc at any point abolishes the response.Nervous system Introduction Terminology Gray matterIn the CNS, the part of aggregations of nerve cell bodiesEmbedded in a network of delicate nerve processes is Known

23、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, funct

24、ion and connectionswithin the CNS are grouped together into nucleus.Ganglion Nerve cells with the same shape, function and connectionsOutside the CNS often are grouped together into ganglion.Nervous system Introduction Terminology White matterIn the CNS, the part that contains mainly bundles of nerve fibers is white matter and the white color is dueTo a rich