Babinski reflex and corticospinal tract lesion

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Spinal ReflexesLu Chen, Ph.D.MCB, UC Berkeley1Simple reflexes such as stretch reflex require coordinatedcontraction and relaxation of different muscle groupsCategories of Muscle Based on Direction of MotionFlexors reduce the angle of jointsExtensors increase the angle of jointsCategories of Muscle Based on MovementAgonist muscle that serves to move thejoint in the same direction as the studiedmuscleAntagonist muscle that moves the jointin the opposite direction2
Muscle SpindlesIntrafusal musclefiberscapsuleSensoryendingsAfferent axonsEfferent axonsGamma motorendings•Small encapsulated sensory receptors that have aspindle-like shape and are located within thefleshy part of the muscle•In parallel with the muscle fibers•Does not contribute to the overall contractileforce•Mechanoreceptors are activated by stretch of thecentral region•Due to stretch of the whole muscle(including intrafusal f.)•Due to contraction of the polar regions ofthe intrafusal fibers3Muscle SpindlesOrganization2 kinds of intrafusal muscle fibers•Nuclear bag fibers (2-3)•Dynamic•Static•Nuclear chain fibers (~5)•Static2 types of sensory fibers•Ia (primary) - central region of allintrafusal fibers•II (secondary) - adjacent to the centralregion of static nuclear bag fibers andnuclear chain fibersIntrafusal fibers stretched(loading the spindle)Sensory ending stretched,increase firingMuscle fibers lengthens(stretched)Sensory ending stretched,increase firingMuscle fiber shortensSpindle unloaded,decrease firing4
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Page 5 and 6: Activation of gamma MN during activ
Page 7 and 8: Summary of Sensory FibersIa•Goes
Page 9: Functions of the Ia inhibitory inte

Babinski reflex and corticospinal tract lesion

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