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1、神经系统对躯体运动的调节Somatomotor function of nervous system,脊髓对躯体运动的调节,运动神经元Motor NeuronsAlpha motor neuronsNeurons that innervate extrafusal muscle fibers.Fast conducting fibers.,Gamma motor neuronsNeurons that innervate the intrafusal muscle fibers.Cause isometric muscle contraction.Only extrafusal muscle
2、fibers are strong and numerous to cause muscle contraction.,运动单位Motor Unit 一个神经元及其所支配的全部肌纤维所组成的功能单位称为运动单位。运动单位数目有大有小，不同运动单位的肌纤维交叉分布，这有利于肌肉产生均匀的张力。,Each somatic neuron together with all the muscle fibers it innervates.Each muscle fiber receives a single axon terminal from a somatic neuron.Each axon c
3、an have collateral branches to innervate an equal#of fibers.,When somatic neuron activated,all the muscle fibers it innervates contract with all or none contractions.Innervation ratio:Ratio of motor neuron:muscle fibers.Fine neural control over the strength occurs when many small motor units are inv
4、olved.Recruitment:Larger and larger motor units are activated to produce greater strength.,屈肌反射和对侧伸肌反射 Crossed-extensor Reflex,Double reciprocal innervation.Affect muscles on the contralateral side of the cord.Step on tack:Foot is withdrawn by contraction.Contralateral leg extends to support body.,当
5、四肢的远端皮肤受到刺激时，被刺激肢体的屈肌发生反射性收缩，称屈肌反射，而同时对的伸肌发生收缩称对侧伸肌反射。,牵张反射stretch reflex当骨骼肌被拉长时，肌肉的感受器(肌梭、腱器)受到刺激，产生神经冲动，通过脊髓反射性地引起被牵拉的肌肉收缩，称牵张反射。腱反射(相位性牵张反射)快速牵拉肌肉时所产生的，使肌肉快速的、同步性的收缩，并产生位移。中枢位于脊髓。,肌紧张(紧张性牵张反射)缓慢和持续地牵拉肌腱，产生经常地、轻度地收缩，产生一种张力阻止肌肉被拉长。抗重力肌(一般为伸肌)的肌紧张对维持正常姿势有重要意义。,Golgi Tendon Organ Reflex,Disynaptic r
6、eflex.2 synapses are crossed in the CNS.Sensory neurons synapse with interneurons in spinal cord.Interneurons have inhibitory synapses with motor neurons.Helps prevent excessive muscle contraction.,脊休克脊动物是指将动物的脊髓与高位中枢离断的动物。可用来研究脊髓的单独功能。首先是由Sherrington采用。实验中还有去大脑动物(中脑上、下丘间、红核之后横断)，会出现伸肌过度紧张；中脑动物(中脑与间
7、脑间横断)，能保持或改正身体在空间的姿势；去皮质动物(去掉大脑皮质)，无意识。,高位中枢对脊髓的影响,在高位中枢离断的脊髓，在手术后暂时失去反射活动的能力，进入无反应状态，这种现象称脊休克，说明高位中枢在正常情况下对脊髓有易化作用。,表现为在横断面下的脊髓所支配的骨骼肌紧张性减低甚至消失，血压下降，外周血管扩张，发汗反射不出现，直肠和膀胱中粪便和尿积聚，这说明动物躯体和内脏反射活动均减退以至消失。,射切诺夫抑制,射切诺夫在实验中发现有食盐结晶刺激蛙间脑的横断面，再给后肢以稀盐酸刺激，发现蛙的反射时延长甚至不出现反射，这种现象称为射切诺夫抑制。说明高位中枢在正常情况下对脊髓有抑制作用。,脑干对躯
8、体运动的调节,脑干网状结构的抑制区和易化区抑制区存在于延髓网状结构的腹内侧部，抑制区及下行通路称为脑干网状结构下行抑制系统。大脑皮质运动区、纹状体、小脑前叶蚓部等下行(锥体外系)的冲动通过网状结构抑制区来完成抑制作用,而且网状结构抑制区有赖于这些高级中枢的下行始动作用。肌肉的紧张性下降,易化区分布于广大的脑干中央区域，包括延髓网状结构的背外侧部、脑桥被盖、中脑的中央灰质及被盖，向上延伸到间脑腹侧的网状结构。这些结构及下行通路称为脑干网状结构下行易化系统。易化区主要接受特异投射系的传入信号的激动作用。肌紧张性明显加强，牵张反射加强,正常情况下，易化区和抑制区活动保持平衡。脑干网状结构下行易化系统
9、和抑制系统都是通过网状脊髓束直接调节运动神经元，从而调节牵张反射，但也通过-运动神经元(通过-环路)，改变肌梭感受装置的敏感性而间接调节运动神经元，从而调节牵张反射。,脑桥的前庭神经核接受来自内耳前庭器官的传入冲动(前庭器官可感受头部位置变化)，而前庭核可将兴奋直接传到脊髓的运动神经元，从而加强四肢肌紧张。,-示抑制系统；+示易化系统,抑制性传导通路：1皮层-延髓-网状通路；2尾核脊髓通路；3小脑-网状通路；4网状脊髓通路。易化性传导通路：5网状-脊髓通路；6前庭-脊髓通路,网状脊髓束,前庭脊髓束,去大脑僵(强)直(decerebrate rigidity)僵直现象去大脑动物在肌紧张活动方面出
10、现亢进的现象，动物四肢伸直、头尾昂起、脊柱挺硬，称为去大脑僵直。去大脑僵直主要是伸肌(抗重力肌)紧张性亢进。,形成原因易化系统的作用失去了抑制系统的平衡。阻断了皮层、尾状核对抑制区的激动作用阻断了皮层、皮层下中枢对易化区的抑制作用易化区又受上行冲动的始动，不受切除的影响,僵直：脑干网状结构易化系统首先加强-运动神经元的活动，使肌梭敏感性增加，传入冲动增加，反射性使运动神经元的兴奋性增强，导致肌紧张加强而出现僵直，称僵直。这是一种过强的牵张反射。,实验证明：切断脊髓相应背根(或以局部麻醉药普鲁卡因)，消除肌梭传入冲动对中枢的作用后，该僵直现象可以消失。,僵直：脑干下行通路直接或经中间神经元作用于
11、运动神经元，其中主要是通过前庭脊髓束实现，通过这种通路而引起伸肌过度紧张现象称为僵直。,实验证明：在前面出现-僵直的动物，切断脊髓背根去大脑僵直现象消失后，若切除小脑前叶，相类似的大脑僵直现象又出现。这是由于内耳前庭器官的传入冲动提高了延髓前庭核的兴奋性，传至脊髓运动神经元，增强了伸肌紧张性的结果。若这时再切除VIII脑神经，僵直又会消失。,大脑皮质对躯体运动的调节,大脑皮质主要运动区第躯体运动区中央前回和旁中央小叶前部(4、6区)，6区位于中央前回之前亦称为运动前区。此区皮质第V层Betz细胞轴突参与组成锥体束。,运动区的功能特点交叉支配，但头面部肌肉的支配多数是双侧性的，象咀嚼肌、喉肌和脸
12、上部肌肉的运动，然而面神经()支配的下部面肌及舌下神经(XII)支配的舌肌主要受对侧支配。因此，在一侧内囊损伤后产生所谓上运动神经元麻痹时，头面部多数肌肉并不完全麻痹，但对侧下部面肌和舌肌发生麻痹；,功能代表区的排列大致呈倒置，头面部位肌肉代表区在底部(头面部代表区内部的安排仍是正立而不是倒置)；功能代表区的大小与运动的精细复杂程度有关与肌肉的大小不成比例，运动愈精细而复杂的肌肉，其代表区亦愈大。,Precentral gyri:Involved in motor control.Body regions with the greatest number of motor innervatio
13、n are represented by largest areas of motor cortex.,第躯体运动区和运动辅助区第躯体运动区与第躯体感觉区重叠。运动辅助区位于半球内侧面、旁中央小叶前方。,大脑皮质对躯体运动的调节皮质的躯体运动调节功能是通过锥体系和锥体外系下传而完成的。,锥体系(pyramidal system)锥体系是指起自大脑与运动有关的区域，由皮质发出直接控制躯体运动的神经通路。,Anterior corticospinal tract 皮质脊髓前束,Lateral corticospinal tract皮质脊髓侧束,锥体束下传的纤维直接与下运动神经元发生突触联系，即构成
14、单突触联系，这只占其中的10-20。,锥体束下传冲动也与脊髓前角运动神经元有联系，以调整肌梭的敏感性，配合运动，两者运动协同控制着肌肉的收缩。,锥体束下行纤维与脊髓中间神经元也有突触联系，从而改变拮抗肌运动神经元之间的对抗平衡，使肢体运动具有合适的强度，保持运动的协调性。锥体系的功能：完成精细、灵巧的随意动作。,锥体外系(extrapyramidal system)锥体系以外的调节躯体运动的下行传导通路。锥体外系的功能调节肌紧张，维持姿势和协调肌肉运动。,特点同时起源于皮质和皮质下结构，皮质起源广泛，皮质下部位包括基底神经节、红核、黑质、脑干网状结构及小脑等；经过多级神经元传递(更换神经元)，
15、最后通过网状脊髓束、红核脊髓束和前庭脊髓束达到脊髓，控制脊髓运动神经元；对脊髓神经元的控制是双侧性。,主要的环路是皮质-脑桥-小脑-背侧丘脑-皮质。小脑可接受大脑下传和来自脑干的信息，同时来自脊髓小脑前、后束的本体感受的信息也输入小脑，从小脑发出的纤维(主要发自齿状核)将信息经中脑、丘脑传入大脑，同时也有一部分止于红核，经红核脊髓束抵脊髓。从上可见，小脑可随时比较运动信息(整合)，返回大脑皮质，影响皮质运动区的活动，对随意运动起调节作用(对运动进行监视和校准的调整作用)。,皮质-脑干-小脑系,皮质纹状体系主要的环路是纹状体-黑质-纹状体和皮质-纹状体-背侧丘脑-皮质。纹状体-黑质-纹状体环路的
16、作用是对纹状体和黑质的活动水平高低起控制作用；皮质-纹状体-背侧丘脑-皮质环路能抑制管理随意运动，及时停止运动区管理的运动，故称“运动抑制环”。,皮质与基底神经节(如纹状体)、中脑的黑质、红核都有联系，其中纹状体与黑质构成密切联系，从一些疾病症状的观察、治疗推测，基底神经节有调节肌紧张、协调姿势反射的功能。舞蹈症和手足徐动症震颤性麻痹(帕金森氏症),舞蹈症和手足徐动症：为不自主的上肢和头部的舞蹈样动作，并伴有肌紧张降低等，表现运动过快，幅度过大。由于患者纹状体中胆硷能神经元和-氨基丁酸能神经元病变，功能减退，对黑质多巴胺能神经元的抑制减少，从而黑质多巴胺能神经元相对亢进所致。,震颤性麻痹(帕金
17、森氏症)：表现伸、屈肌同时强直收缩，全身肌紧张增强，随意运动减少，动作缓慢，面部表情呆板，同时出现静止时四肢震颤，情绪激动时加剧，主动运动时减少，入睡时停止(肌张力过强，运动减少)。黑质多巴胺能神经元功能被破坏(DA递质系统受损)，导致乙酰胆硷递质系统功能亢进，以致到脑干网状结构功能加强所致。用左旋多巴以增强多巴胺合成，或用M型受体阻断剂阻断ACH的作用，对该病有治疗作用。,黑质纹状体环路示意图,神经系统对内脏活动的调节Neuroregulation of visceral activity autonomic nervous system,植物性神经系统(vegetative nervous
18、 system)及对内脏活动的调节,植物性神经系统又称为自主神经系统Autonomic Nervous System(ANS)Innervate organs not usually under voluntary control.Effectors include cardiac and smooth muscles and glands.Effectors are part of visceral organs and blood vessels.,Characteristic of the ANS,2 neurons in the effector pathway.1st neuron
19、has its cell body in gray matter of brain or spinal cord.Preganglionic neuron.Synapses with 2nd neuron within an autonomic ganglion which extends to synapse with effector organ.Postganglionic neuron.,Somatic Motor Neurons?,Somatic Motor Neurons,Cell bodies in CNS.Conduct APs along single axon from s
20、pinal cord to neuromuscular junction.Usually under voluntary control.,Autonomic NeuronsPreganglionic autonomic fibers originate in midbrain,hindbrain(medulla,and pons),and upper thoracic to 4th sacral levels of the spinal cord.Autonomic ganglia are located in the head,neck,and abdomen.Presynaptic ne
21、uron myelinated and postsynaptic neuron unmyelinated.,Visceral Effector OrgansInvoluntary effectors are somewhat independent of their innervation.Denervation hypersensitivity:Damage to autonomic nerve makes its target tissue more sensitive than normal to stimulating agents.Cardiac and many smooth mu
22、scles can contract rhythmically in absence of nerve stimulation.Maintain resting tone.,Divisions of the ANS,Sympathetic Nervous System(SNS)Parasympathetic Nervous System(PNS)Both have preganglionic neurons that originate in CNS.Both have postganglionic neurons that originate outside of the CNS in ga
23、nglia.,Sympathetic Nervous System(SNS),Myelinated preganglionic exit spinal cord in ventral roots at T1 to L2(L3)levels.Travel to ganglia at different levels to synapse with postganglionic neurons.Divergence:Preganglionic fibers branch to synapse with numerous postganglionic neurons.,Convergence:Pos
24、tganglionic neuron receives synaptic input from large#of preganglionic fibers.Mass activation:Divergence and convergence cause the SNS to be activated as a unit.,Axons of postganglionic neurons are unmyelinated to the effector organ.Preganglionic neuron is short.Post-ganglionic neuron is long.,Sympa
25、thetic-Origin,Thoracolumbar(between T1&L2),Sympathetic chain交感干及神经节,Superior mesenteric ganglion肠系膜上神经节,inferior mesenteric ganglion肠系膜下神经节,Greater splanchnic nerve内脏大神经,lesser splanchnic nerve内脏小神经,(下颌下腺和舌下腺腮腺),(泪腺和鼻粘膜),Ganglia close to spinal cord,Short,lightly myelinated preganglionic neurons,Lon
26、g,unmyelinated postganglionic neurons,肾上腺髓质,Adrenal medulla secretes epinephrine and norepinephrine when stimulated by the SNS.Innervated by preganglionic sympathetic fibers.Stimulated by mass activation,Adrenal medulla,Parasympathetic Nervous System,Preganglionic fibers originate in midbrain,medull
27、a,and pons;and in the 2-4 sacral levels of the spinal cord.Preganglionic fibers synapse in ganglia located next to or within organs innervated.,Do not travel within spinal nervesDo not innervate blood vessels,sweat glands,and arrector pilli muscles(竖毛肌).4 of 12 pairs of cranial nerves contain pregan
28、glionic parasympathetic fibers.Preganglionic fibers are long,postganglionic fibers are short.,Vagus:Innervate heart,lungs,esophagus,stomach,pancreas,liver,small intestine and upper half of the large intestine.Preganglionic fibers from the sacral level innervate the lower half of large intestine,the
29、rectum,urinary and reproductive systems.,Parasympathetic-Origin,Nerve fibers emerge from brain&sacrum,睫状神经节,翼腭神经节,下颌下神经节,耳神经节,Ganglia close to or on target organs,Preganglionic neurons-long,Post ganglionic neurons-short,Sympathetic Effects,Fight or flight response.Release of norepinephrine from post
30、ganglionic fibers and epinephrine from adrenal medulla.Mass activation prepares for intense activity.Heart rate increases.Bronchioles dilate.glucose increases.,Parasympathetic Effects,Stimulation of separate parasympathetic nerves.Release ACh.Relaxing effects:Decrease heart rate(HR).Dilate blood ves
31、sels.Increase GI(胃肠)activity.,“Fight or Flight”Activated during emergencies,exercise or vigorous physical activityRevs up body to respond to situations that upset homeostasis,“Rest&Digest”Reduces energy usePromotes:digestion of foodstorage of energy elimination of wasteshomeostasis,Sympathetic,Paras
32、ympathetic,Organs with Dual Innervation,Most visceral organs receive dual innervation(innervated by both sympathetic and parasympathetic fibers).Antagonistic effects:Actions counteract each other.Heart rate.,Complementary:Produce similar effects.Salivary gland secretion.Cooperative:Cooperate to prod
33、uce a desired effect.Micturition排尿.,Neurotransmitters and NT Receptors,Neurotransmitters,ACh is NT for all preganglionic fibers of both sympathetic and parasympathetic nervous systems.ACh is NT released by most postganglionic parasympathetic fibers.Transmission at these synapses is termed cholinergi
34、c(胆碱能).,NT released by most postganglionic sympathetic nerve fibers is norepinephrine(NE,去甲肾上腺素).Transmission at these synapses is called adrenergic(肾上腺素能).Epinephrine(E,肾上腺素)released by the adrenal medulla is synthesized from the same precursor as norepinephrine.Collectively called catecholamines(儿
35、茶酚胺).,酪氨酸,二羟(基)苯丙氨酸,左旋多巴,多巴胺,Adrenal medulla:releases epinepherine&norepinepherine into blood.,Postganglionic neurons:release norepinepherine at target organs.Attention:支配汗腺、骨骼肌的交感节后舒血管纤维为胆碱能纤维。,Other Autonomic NTs,Certain postganglionic autonomic axons produce their effects through other NTs.ATPVIP
36、NO,Receptors,Found on dendrites&cell bodies of postganglionic neurons of both sympathetic and parasympathetic divisions of ANS.Found on parasympathetic target organs.Found on skeletal muscle cells regulated by motor neurons.,Cholinergic Receptors(胆碱能受体),Muscarinic receptors(M型受体，毒蕈碱型受体),On all targe
37、t organs of parasympatheticAch binds to receptor.Requires the mediation of G-proteins.Beta-gamma complex binds to chemical K+channel,opening the channel.,May excite or decrease activity depending on targetDecrease HR.Decrease force of contraction of the heart.Produce bronchiole constriction.Increase
38、s digestive activity including secretions&peristalsis.Causes constriction of Iris(虹膜),Blocking AgentsBlocking agents are chemicals which bind to the receptors on target organs and prevent the normal neurotransmitter from binding.Blockers:Atropine(阿托品).,Nicotinic receptors(N型受体，菸碱型受体),On skeletal mus
39、cle cells(N2)On postganglionic dendrites&cell bodies in both sympathetic¶sympathetic(N1)ACh binds to 2 nicotinic receptor binding sites.Opens a Na+/K+channel.Almost always excite,Blockers:Tubocurarine(筒箭毒)Interfere with stimulatory or depressing effects of neurotransmitters by blocking the recep
40、tors on target organs.,Normal neurotransmitter cant bind with receptor because blocker covers the binding site.,Located only on sympathetic target organs.,Adrenergic Receptors(肾上腺素能受体),Respond only to norepinepherine released by postganglionic neurons(precise effects)or,Epinepherine&norepinepherine
41、released by adrenal medulla into blood(general effects).,Has both excitatory and inhibitory effects.Responses due to different membrane receptor proteins.1:constricts vascular smooth muscles2:contraction of smooth muscle 1:increases HR and force of contraction2:relaxes bronchial smooth muscles,Beta
42、receptorsProduce their effects by production of cAMP.NE binds to receptor.Alpha G complex activates adenylate cyclase,producing cAMP.cAMP activates protein kinase,opening ion channels.,Alpha1 receptorsProduce their effects by the production of Ca+.Epinephrine binds to receptor.Ca+binds to calmodulin
43、.Calmodulin activates protein kinase,modifying enzyme action.,Adrenergic BlockersBeta 1 and 2 blockersExamples:Propranolol(心得安)Beta 1 blockers on heartprevent heart rate increase&arrhythmias in cardiac patients without interfering with other sympathetic effects.Examples:Practolol(心得宁),Beta 2 blocker
44、sExamples:Butoxamine(心得乐),Alpha blockersDecrease blood pressure in patients with hypertension without interfering with other sympathetic effects.Phentolamine(酚妥拉明).,效应器上有仅有受体，有的仅有受体，有的、受体均有。二种受体对NE和E的作用强度有差异NE：受体作用强，而对受体作用弱，临床上用作升压药；E：、受体作用都强，临床上用作强心药。,effects,Alpha 1In walls of blood vessels leadin
45、g to places other than skeletal muscles,brain&lungs.Not on heart(cardiac muscle)Alpha 2On membranes of platelets.,Beta 1On heart(cardiac muscle)&kidneys Beta 2On coronary arteries,bronchioles&on smooth muscle walls of digestive&urinary systems,Alpha 1Excites(constricts)smooth muscles in certain bloo
46、d vessels&in sphincters directing blood to skeletal musclesDilates pupils.Alpha 2Promotes blood clotting,Beta 1Cardiac Muscle Increases heart rate&strengthBeta 2Depresses(dilates)smooth muscle in bronchioles&coronary arteries increasing blood flow to heart and air flow to lungs.,Control by Higher Br
47、ain Centers,脊髓对内脏活动的调节,交感和部分副交感神经发源于脊髓的侧角及相当于侧角的部位，因此脊髓可以成为内脏反射活动的初级中枢。,低位脑干对内脏活动的调节,中脑和延髓发出的、对脑神经中的副交感神经。脑干网状结构中存在许多与内脏活动功能有关的神经元，其下行纤维支配脊髓，调节着脊髓的植物性神经功能。许多基本生命活动的反射调节在延髓水平已能初步完成，所以有人称延髓为基本生命中枢。,下丘脑对内脏活动的调节,体温调节体温调节中枢在下丘脑。摄食行为调节下丘脑存在摄食中枢(feeding center)，位于外侧区，饱食中枢(satiety center)，位于内侧区。,水平衡调节水平衡包括水
48、的摄入与排出，人体通过渴感引起摄水，而排水则主要取决于肾脏的活动。下丘脑内饮水中枢靠近摄食中枢，下丘脑控制排水的功能是通过改变抗利尿激素的分泌来完成的，其由视上核的神经元合成。下丘脑控制摄水的区域与控制抗利尿激素分泌的核团在功能上有联系，两者协同调节水平衡。,对腺垂体激素分泌的调节下丘脑内有些神经元能合成调节腺垂体激素分泌的肽类化学物质。对情绪反应的影响情绪是中枢神经系统的高级功能，在人类是一种心理现象，常伴有植物性神经功能、躯体运动功能及内分泌功能的变化。植物性功能的变化主要表现为交感神经活动亢进。,大脑皮质对内脏活动的调节,Sensory input transmitted to brai
49、n centers that integrate information.Can modify activity of preganglionic autonomic neurons.Cerebral cortex and limbic system:Responsible for responses to emotion.,脑的高级功能Advanced function of the brain,条件反射,巴甫洛夫(18491936)的研究工作可以分成前后三个互相交叉一致的时期1874-883研究血液循环和胰腺的作用；1879-1904致力于消化生理学的研究，1904年获诺贝尔医学和生理学奖
50、；1904-献身于研究反射和人的高级神经活动，创立条件反射理论，提出人脑有两个信号系统。,非条件反射(unconditioned reflex)非条件反射是种族进化过程中形成的先天性反射或者说是在系统发育过程中形成而遗传下来的，不学即会。反射通路是固定的，不易改变。引起非条件反射的刺激为非条件刺激。非条件反射是低级的神经活动，同种动物有相同的非条件反射。,条件反射的概念,条件反射(conditioned reflex)条件反射是动物在生活过程中一定条件下形成的，后天形成具有很大的易变性和适应性，反射弧是暂时的引起条件反射的刺激是条件刺激条件反射是高级神经活动,条件反射的形成(建立),无关刺激(
