1、Neurotransmitters and Receptors The neurotransmitters are the chemical substances which bring the information from one neuron to another.The nerve endings have been called biologic tranducers,that convert electrical energy into chamical energy.This conversion process involves the neurotransmitters.A
2、 substance is a transmitter if it is1.distributed in the synaptic knob,and its distribution parallels that it receptors in postsynptic cell,2.There are the synthetic enzymes in presynaptic neuron and the catabolizing enzymes in the synapse.Criterions3.released from slice of brain regions into the sy
3、naptic cleft in vitro.4.produces effects on target neurons when applied to their membrance by mesns of a micropipette(微电泳微电泳).5.The agonist can produce the same effects;but antagonist can block the role of transmitters.Acetycholine and cholinergic receptorsSynthesis and catabolismCholineAcetyl-CoAAc
4、etylcholineCholine acetyltransferaseAcetylcholinesteraseCholineAcetateAcetylcholinergic receptors Muscrinic receptors(M-receptor)smooth muscle,gland and cardiac muscle Atropine inhibiting the cardiac muscle,exciting the smooth muscle&gland Nicotinic receptors (N-receptor)motor ending-plate(N2),posts
5、ynaptic membrane(N1),N1:hexamethonium(六烃季胺六烃季胺),N2:decame-thonium N2:exciting skeletal muscle,N1 exciting the postsynaptic neuron in gangliaLocationsAntagonistNorepinrphrineNorepinephrine BiosynthesisTyrosineDopaDopamineNorepinephrineTyrosine hydroxylase Dopa decarboxylaseDopamine-hydroxylase Phenyl
6、alamineNorepinrphrinergic Receptors -receptors 1&2 Deoxynorepinephrine phentolamine()prazosin(1)yohimbine(2)-receptors1,2,3Isoproterenolpropranonol()atenolol(1)butoxamine(2 Ther are two types of the norepinephrinergic receptors binded with norepinephrine and epinephrine.AgonistAntagonistTypesDopamin
7、eDopamine and its receptors are located mainly in central system.It is secreted by neurons that originate in the substantia nigra.The terminations of these neurons are mainly in the straital region of the basal ganglia.The effect of dopamine is usually inhibitory.There are 5 sub-types of dopaminergi
8、c receptors;D1,D2,D3,D4,D5 form.SerotoninIt is secreted by nuclei that originate in the median raphe of the brain stem and projects to many brain areas,especially to the dorsal horns of the spinal cord and to the hypothalamus.Serotonin acts as an inhibitor of pain pathways in the cord,and it ia also
9、 believed to help control the mood of the person,perhaps even to cause sleep.Opioid Peptides Enkephalin and endorphinsThey are probably secreted by nerve terminal in the spinal cord,the brain stem,the thalamus,and the hypothalamus.These probably act as excitatory transmitters to excite another syste
10、m that inhibits the transmission of pain.Three opiate receptors are established:receptorReflex Concept:A reflex is an automatic response to a stimulus,carried out by a relatively simple neuronal network.Form:Unconditioned reflex,Conditioned reflex Unconditioned reflex:protective reflex;feeding refle
11、x;sexual reflex Conditioned reflexes a.form:classic conditioned reflex,electrocortical conditioning,operant conditioning b.mechanism:a functional pathway is developed during the conditioning period.notes:conditioned stimulus,unconditioned stimulus,internal and external inhibition,positive and negati
12、ve reinforcement,habituationReflex ArcSensory Function Of Nervous SystemSensory PathwaysPosterior column pathwayStep 1:The touch and proprioception impulses reach the spinal cord through the dorsal roots of spial nerves.Inside the spinal cord,the axons asend in the dorsal column to the mudulla.Step
13、2:They synapse in the gracile and cuneate nuclei in the mudulla,and the axon of the nerves in these nucleis cross over to the opposite side of the brain stem and asend to the thalamus.Touch,vibration,pressure,and proprioceptionNuclei in medulla oblongataNuclei in thalamusLateral&ventral spino-thamic
14、 tracts1.The pain and tempreture fibers that enter the dorsal columns pass to the dorsal horn,where the fibers synapse on second-order neurons.2.The axons from these neurons cross the midline and asend in the anterolateral column of the spinal cord to the thalamus,and synapse on the specific sensory
15、 relay nuclei of the thalamus.3.There is a major input from the anterolateral system into the mesencephalic reticular formation.Thus sensory input activities the reticular activitiny system,which in return maintains the cortex in the alert atate.Lateral&ventral spino-thamic tractsNuclei in thalamusL
16、ateral spino-thalamic tractVentral spino-thalamic tractThalamus All sensory informations enter the thalamus before transmission to the cereberal cortex (exception to olfactory signals).The thalamic functions is a vital way station for the receipt of sensory impulses from the body.From the thalamus,t
17、his sensory information is relayed(projected)to appropriate areas of the cerebral cortex.In addition,the thalamus integrates and transmits nerve impulses to subcortical areas,and receives afferent impulses that originate in the cerebral cortex,cerebellum,and basal ganglia.Thamamic Nucleis The thalam
18、ic nucleis can be divided into 3 groups:Sense-relay nuclei The specific sense-relay nuclei,which relay auditory,visual and somatesthetic impulse to the auditory,visual cortex and postcentral gyrus.2.Associated nuclei Which are concerned with the integration of movement,and the connection of the all
19、senses.3.Intralaminar nuclei:These nucleus dont project directly to central areas of the cortex.The intralaminar nuclei transmits nerve impulses to subcortical areas before transmission to the cereberal cortex.and then projecte diffusely to the cortex and maintain wakefulness.Thalamus The thalamus i
20、s the final relay point for all asending sensory information,other than olfaction,that will reach our conscious awareness.It acts as a filter,passing on to the primary sensory cortex only a small portion of the arriving sensory information.The thalamus also plays a role in the coordination of volunt
21、ary motor commands.Projection System Specific projection system from the sensory relay and connective nucleis projecting to the specific areas of cortex inducing the specific sensory.Non-Specific projection systemfrom the third thalamic nucleisprojecting diffusely to the cortexmantaining the awarene
22、ss stateCortical Represention Somatic sensory area I is located the postcentral gyrus.Somatic SensationFunctional Characteristics of Somatic sensory area I 1.The parts of the body are represented in order along this area,with the legs on the top and the head at the feet of the gyrus.2.The size of th
23、e cortical receiving area for impulse from a particilar part of the body is proportional to the number of receptors in the part.3.The legs and trunk are represented by the opposite side of the postcentral gyrus.Somatic sensory area II The somatic sensory area II is located in the superior wall of sy
24、lvian fissure（大脑侧裂）大脑侧裂）.The head is represented at the inferior end of the postcentral gyrus,and the feet at the bottom of the slyvian fissure.The represention of the body parts is not as complete or detailed as it is in the postcentral gyrus.Propriocepton(本体感觉）本体感觉）Proprioceptive information is tr
25、ansmitted up the spinal cord in the dorsal column.A good deal of the proprioceptive input goes to the cerebellum,but some passes via the medial lemnici and thalamic radiation to the cortex.Temperature The temperature sense organs are naked nerve endings.Cold receptors respond from 10 to 38 o C.Warm
26、receptors respond from 30 to 45 o C.The impulses from these recetors relay information to the postcentral gyrus via the lateral spinothalamic tract and the thalamic radiation.Pain Pain is a very unpleasant feeling produced by the harmful stimulations.The sence organs for pain are the naked nerve-end
27、ings.Pain impulses are trainmitted to the centrol nervous system by 2 fibers systems,small myelinated A fibers and unmyelinated C.Fast Pain Slow Pain“bright”sharp localized followed by a dull,intense,diffuse,and unpleasure feeling.trainsmitted by A fibers“cautery”slow poorly localized followed by na
28、usea,throw up,cardiovescular and respiratory changes.trainsmitted by C fibers Visceral Pain&Referred Pain Visceral pain is the slow pain that is poorly localized,unpleasant,and associated with nausea and autonomic symptoms.Referred pain Irriation of a viscus frequently produces pain in some somatic
29、structure that may be a considerable distance away.Locations of Referred PainFormation of Referred PainViscusViscusSomatic structureSomatic structureTo brainTo brainEvoked cortical potentials Definition:The electrical events that occur in the cortex after stimulation of a sence organ can be monitred
30、.Component:a.prirmary response(large pyramidal cells)b.after discharge (cortex-thalamic circuit)Waves of Evoked Cortical PotentialsElectroencephalogram(EEG)The record of the variations in potential recorded from the brain is called the EEG.The EEG can be recorded with scape electrodes through the un
31、opened skull or with electrodes on or in the brain.The term electrocorticogram(EcoG)is sometimes used to refer to the record obtained with electrodes on the pial surface of the cortex.Method of Recording EEGForms Of EEG Waves 1.alpha waves(alpha rhythm):In an adult human at rest with mind wandering
32、and eyes closed,the most prominent component of the EEG is a fairly regular pattern of waves at a frequency of 812/s and an amplitude of about 50V when recorded from the scalp.2.beta waves:at a frequency of 1430/s,an amplitude of about 50V,recorded from parietal and frontal region of the scap;3.thet
33、a waves:This wave occurs in children,emotional stress,brain disorersd,and is generated in hippocampus in experimental animals.4.delta waves:below 3.5/s;occurs in deep sleep,infancy,very serious organic brain disease.EEG Waves Alpha Block:When the eyes are opened,the alpha rhythm is replaced by fast,
34、irregular low-voltage with no dominant frequecy.This phenomenon is called alpha block.alpha wavesEyes openEye closealpha waves Sleep Phases of sleep (1)Slow wave sleep:A person asleep first erters this stage,it lasts about 80120 minutes.(2)Desynchronized sleep:lasts about 20 to 30 minutes,and usuall
35、y appearson the average every 90 minutes SWS Slow一一synchronizedeasily FWS Fast irregular irregular+desynchronized difficutlyEye movement Blood pressureHeart rateRespirationSenseSkeletal muscles relaxTension of muscleDreamingPattern of EEGArouseMechanism of SleepControl Of Posture&Movement-Elementary
36、 Principles Of Movement ControlMotoneurons Of Spinal Cord&Motor Unit1.Motoneurons of the spinal cord motoneurons large motoneurons fast muscle small motoneurons slow muscle motoneurons intrafusal fibers of muscle spindle.2.Motor unit:All the muscle fibers innervated by a by a single motor nerve fibe
37、r are called a motor unit.Stretch Reflex1.Definition:When the skeletal muscle with an intact nerve supply is stretched,it contracts.This response is called the stretch reflex.2.Form:tendon reflex and tonic stretch refle(muscle tonus)Tendon reflex Sudden stretch of a muscle causes reflex contraction
38、of the same muscle,and this opposes further stretch of the muscle.Tonic stretch reflex(muscle tonus):Slow and constant stretch of a muscle causes tonic contraction of the muscle,and this maintains the posture of the body.Muscle TonusMechanism of Stretch ReflexMuscle spindle&Golgi organs Muscle spind
39、le:Each spindle is built around three to ten small intrafusal muscle fibers,and it is a very small skeletal muscle fiber.The central region of each fiber has either no or few actin and myosin filaments.The central portion of the muscle spindle is the sensory receptor area of the spindle and can sens
40、e the length of the muscle.Golgi organ:The Golgi organ senses the tension of the muscle,and its afferents are the Ib fibers.Effects of -motoneurons The efferents fibers of the-motoneurons innervate the intrafusal muscle,and control the sensitivity of the mulscle spindles detecting the change in leng
41、th of the muscle.When intrafusal muscles contract,the sensitivity of the muscle spindles for muscle length is increased,and the afferent impulses of the muscle spindles increase.Control of Voluntary MovementCortical Motor Areas Localization:The cortical motor areas is located at precentral motor are
42、a (4 and 6 area).Characteristics of motor areas(1)The various parts of the body are represented in the precentral gyrus,with the feet at the top of the gyrus and the face at the bottom.(2)The facial area is represented bilateral,but the rest of the representation is unilateral.(3)The cortical repres
43、entation of each body part is proportionatein size to the skill with which the part is used in fine.The cortical representation of each body partCorticospinal TractsLateral corticospinal tract(80%)The nerve fibers that cross the midline in the medullary pyramids and form the lateral corticospinal tr
44、act make up about 80%of the fibers in the corticospinal pathway.Anterior corticospinal tract(20%)The remaining 20%make up the anterior corticospinal tract,which does not the midline until the level at which it synapses with motor neurons.Function Of Corticospinal TractThese fibers end directly on the lateral motor neuron in the ventral horn of spinal cord in human being,and control the distal limb muscle and hence skilled movements.返回返回
