生理学英文版教学课件：nervous system-4-2016

1、Nervous System:Control of Somatic MovementPUMC & CAMS Xue GaoTypes of Motor Neuron motor Neuron: Conducted by type A motor nerve fiber (14 m), innervated larger skeletal muscle fiber (Extrafusal Fibers) motor Neuron : Conducted by type A nerve fiber (5 m) , innervated special skeletal muscle (Intraf

2、usal Fibers) motor Neuron : Conducted by type A & A motor nerve fiber, but function is unknownFinal Common Pathway( motor Neuron)Final Common Pathway Sensory Receptor (Proprioception) Information from Cerebral CortexSpinal Motor Neuron“Somatic movement”Motor Unit A kind of functional unit composed b

3、y a single alpha motor neuron with all (Extrafusal) muscle fibers it innervatesOne muscle may have many motor units Motor unit & Muscle All skeletal muscle fibres or cells in one motor unit contract synchronously, so called “All or None” How about the one skeletal muscle contract? “All or None” or N

4、ot? Sensory Receptor (Proprioception) Information from Cerebral CortexSpinal Motor Neuron“Somatic movement” Postural movementVoluntary movement Spinal Cord Brain Stem Cerebral Cortex Basal Ganglion Cerebellum Postural Reflex: Reflexive movement controlled by CNS that maintain the body equilibration

5、regulated by changing the muscle tension or muscle lengthControl of postural movement Spinal Cord - Postural Reflex Spinal animal: Animal which Spinal cord is frequently transected in the 5th segment of neck Spinal shock: When the spinal cord is suddenly transected in the upper neck, cord reflexes(t

6、endon reflex, flexor reflex ,crossed extension reflex) immediately become depressed to the point of total silence, bladder & rectal reflexes absence, no sweating, blood pressure decrease Not the injury itself in the spinal cord Loss of the regulation & control of higher nervous centerCause of Spinal

7、 ShockPostural Reflex -Spinal Cord Crossed Extension Reflex Stretch Reflex Inverse Stretch Reflex Intersegmental Reflex: Scratching ReflexCrossed Extension Reflex The reflex occur when you step on a sharp object There is a rapid lifting of the affected foot (Ipsilateral Withdrawal Reflex, Flexor Ref

8、lex, not a postural reflex) While the contralateral response activates the extensor muscles of the opposite leg (Crossed Extension Reflex, support the body weight shifted)Flexor Reflex& Flexor Reflex& Crossed Extension Reflex Stretch Reflex Definition: Whenever the muscle is stretched suddenly, exci

9、tation of a kind of reflex cause a contraction of the same muscle Sensory Receptor: Muscle Spindle Structure of Muscle Spindle The extrafusal muscle fibers are innervated by motor neuron The intrafusal muscle fibers are innervated by motor neurons Intrafusal Muscle Fibers (sensory part) Inside Struc

10、ture of Muscle Spindle Sensory Part locate in the middle of muscle spindle Intrafusal Muscle Fibers (sensory part) Nuclear Bag Fiber: Innervated by Type Ia fibers (Annulospiral ending), Primary sensory endings, Stimulated by both the rate & amount of stretch Nuclear Chain Fiber: Innervated by Type I

11、a & II fibers (Annulospiral & Flower-Spray ending) , Secondary sensory endings, stimulated only by degree of stretchInside Structure of Muscle Spindle Intrafusal Muscle Fibers (Movement Part)“ motor neuron” Plate ending at nuclear bag fiber Trail ending at nuclear chain fiber Inside Structure of Mus

12、cle Spindle Movement part locate in the two terminal of muscle spindleMuscle spindle working mechanism“Detecting muscle length” motor neuron is the main motor neuron causing muscle contraction motor neuron do not directly causing muscle contraction, but may increase muscle spindle sensibility by mai

13、ntaining its length or tension Stretch ReflexTwo Types of Stretch Reflex 1.Tendon Reflex 2. Muscle Tonus1. Tendon Reflex - Knee Jerk Caused by rapid stretch of the muscle tendon Transmitted from the Ia sensory nerve React immediately within 0.7 ms Causes an instantaneous, strong reflexive contractio

14、n of the same muscle Monosynaptic reflex Sensory receptor: muscle spindleTendon Reflex (Phasic Stretch Reflex) Clinical Importance Reflex decrudescence or missing: Injury of reflex Arc Reflex accentuation: Disease of higher nervous center Muscle is stretched, muscle spindle records the change & send

15、s signals to the spine. Stretch reflex causes the stretched muscle to contract to resist muscle length change. Muscle spindle helps to protect the muscle from injury 2. Muscle Tonus (Static/Tonic Stretch Reflex) Caused by a weaker & continue stretch of the muscle spindle Transmitted from the Ia & II

16、 sensory nerve Motor unit at same muscle is Non-synchronized contraction Polysynaptic reflex Maintaining the posture of the body for a long time Sensory receptor: muscle spindle Importance: combat effect of gravity & maitain body upright position, protect the muscle from injury 2. Muscle Tonus (Stat

17、ic/Tonic Stretch Reflex) Inverse stretch reflex Sensory receptor：Golgi Tendon OrganStructure of Tendon OrganLocated in the muscle fibers & muscle tendon junctionConnective tissue encapsulating collagen fibers & nerve endings1015 muscle fibers are usually connected to each tendon organInvervated by I

18、b afferent nerve fiberSensitive to TensionTendon Organ: Reflex ArchActivation of Tendon Organ(-)x Muscles contract will stimulate golgi tendon organ. Golgi tendon organ records the change in muscle tension. When this tension exceeds a certain threshold, it triggers the lengthening reaction which inh

19、ibits the muscles from contracting & causes them to relax. When muscle tension increases moderately during muscle contraction Tendon organ is activated & type Ib afferent nerve impulse is transmitted to the spinal cord motor neurons in the spinal cord supplying the contracting muscle are inhibitedPr

20、ocess of Tendon Organ ActivationTendon organ detects Muscle Tension Importance of inverse stretch reflex A tension feedback system that can adjust the strength of contraction during stretch reflex Help ensure termination of muscle contraction A protective mechanism to prevent tearing of the muscle o

21、r avulsion of the tendon from its attachments to the bone(Anti-Stretch Reflex,Reverse Stretch Reflex )Brain Stem - Control of Posture Brain Facilitated & Inhibitory areaAreas in the cat brain: where stimulation produces facilitation (+) or inhibition (-) of stretch reflexes. cerebral cortex Basal ga

22、nglia Cerebellum Reticular inhibitory areaReticular facilitated area Vestibular nuclei1. Reticular inhibitory area2. Reticular facilitated area (+) is stronger than (-) Brain Stem Facilitated & Inhibitory areaDecerebrate Rigidity Decerebrate Rigidity: Transection of the brainstem at mesencephalon le

23、vel, between superior colliculus & inferior colliculus Over strengthened stretch reflexDecerebrate RigidityDecorticate RigidityPostural Reflex -Brain Stem Attitudinal Reflex Tonic Labyrinthine Reflex Tonic Neck Reflex Righting Reflex Not obviously appeared in normal person duo to the depression from

24、 higher nervous centerTonic Labyrinthine Reflex Tonic Neck ReflexTonic Neck ReflexRighting Reflex Labyrinthine righting Reflex Optical righting Reflex Neck righting Reflex Sensory Receptor (Proprioception) Information from Cerebral CortexSpinal Motor NeuronSomatic movement Postural movementVoluntary

25、 movement Spinal Cord Brain Stem Cerebral Cortex Basal Ganglion CerebellumControl of voluntary movements Cerebral Cortex Basal Ganglia Cerebellum Cerebral Cortex - voluntary movement 3 main cortical motor area: Primary Motor Cortex (Area 4) Premotor Areas (Area 6) Supplementary motor area It has pre

26、dominant influence on the opposite side of the body (but craniofacial muscle, Except musculi linguae & subjacent facial muscles, controlled by two side) Face & fingers have large representative area，the larger area representative in the cortex，the more skilled action can be achievedDescendent Moveme

27、nt Tracts Corticobulbar tract Corticospinal TractLateral Corticospinal Tract (80%) Control conscious skilled movementsVentral Corticospinal Tract (20%) Control posture maintenance & clumsy movementLateral TractVentral TractBabinski Sign(Sign of injury at Corticospinal Tract) Flaccid paralysis: Depri

28、vation of voluntary activity Subsidence of stretch reflex Spastic paralyses: Deprivation of voluntary activity Accentuation of stretch reflexInjury of Descendent Movement Tracts Basal Ganglia - Voluntary Movement Basal Ganglia are a group of nuclei under cerebral cortex Corpus Striatum: -Caudate Nuc

29、leus - Putamen- Globus Pallidus Substantia NigraWide CorticesMotor CorticesNew Corpus striatum D2 D1Substantia NigraDA(-)DA(+)GABA(-) Globus PallidusInternal SegmentThalamusGABA(-)(+)Globus PallidusExternal SegmentGABA(-) Subthalamus NucleusGABA(-) Glu(+)Glu(+)Glu(+)Direct PathwayIndirect PathwayDis

30、ease in Basal Ganglia Parkinsons disease (Paralysis Agitans) Huntingtons disease (Chorea)Clinical Feature: 1. Slowness of Movement -Difficulty in Movement Initiation & Cessation2. Random movement decrease 3. Resting Tremor4. RigidityParkinsons Disease Cause of Parkinsons DiseaseWide CorticesMotor CorticesNew Corpus striatum D2 D1Substantia NigraDA(-)DA(+)GABA(-) Globus PallidusInter