11 Motor system I 1 Introduction • Skeletal muscle contraction is initiated by lower motor neuron • Lower motor neuron is a part of local reflex circuits • The information from several sources is integrated in the lower motor neuron – Higher levels of CNS ➢Upper motor neuron, tectum, n. ruber, brain stem – Proprioception http://www.frontiersin.org/files/Articles/42416/fnhum-07-00085- HTML/image_m/fnhum-07-00085-g001.jpg 2 Introduction • Skeletal muscle contraction is initiated by lower motor neuron • Lower motor neuron is a part of local reflex circuits • The information from several sources is integrated in the lower motor neuron – Higher levels of CNS ➢Upper motor neuron, tectum, n. ruber, brain stem – Proprioception http://www.frontiersin.org/files/Articles/42416/fnhum-07-00085- HTML/image_m/fnhum-07-00085-g001.jpg 3 Introduction • Skeletal muscle contraction is initiated by lower motor neuron • Lower motor neuron is a part of local reflex circuits • The information from several sources is integrated in the lower motor neuron – Higher levels of CNS ➢Upper motor neuron, tectum, n. ruber, brain stem – Proprioception http://www.frontiersin.org/files/Articles/42416/fnhum-07-00085- HTML/image_m/fnhum-07-00085-g001.jpg 4 Introduction • Skeletal muscle contraction is initiated by lower motor neuron • Lower motor neuron is a part of local reflex circuits • The information from several sources is integrated in the lower motor neuron – Higher levels of CNS ➢Upper motor neuron, tectum, n. ruber, brain stem – Proprioception http://www.frontiersin.org/files/Articles/42416/fnhum-07-00085- HTML/image_m/fnhum-07-00085-g001.jpg 5 Introduction • Skeletal muscle contraction is initiated by lower motor neuron • Lower motor neuron is a part of local reflex circuits • The information from several sources is integrated in the lower motor neuron – Higher levels of CNS ➢Upper motor neuron, tectum, n. ruber, brain stem – Proprioception http://www.frontiersin.org/files/Articles/42416/fnhum-07-00085- HTML/image_m/fnhum-07-00085-g001.jpg 6 Lower motor neuron • α motoneuron – Innervation of contractile elements – Extrafusal fibers – Muscle contraction • γ motoneuron – Innervation of muscle spindles – Intrafusal fibers – Alignment of muscle spindles – Gamma loop • β motoneuron – Both extrafusal and intrafusal fiberrs http://epomedicine.com/wp-content/uploads/2016/07/gamma-loop.jpg 7 Lower motor neuron Topography http://www.slideshare.net/drpsdeb/presentations 8 Motor unit • A typical muscle is innervated by about 100 motoneurons which are localized in motor nucleus • Each motoneuron innervate from 100 to 1000 muscle fibers and one muscle fiber is innervated by a single motoneuron • The ensemble of muscle fibers innervated by a single neuron and corresponding motoneuron constitutes the motor unit 9 Motor unit • A typical muscle is innervated by about 100 motoneurons which are localized in motor nucleus • Each motoneuron innervate from 100 to 1000 muscle fibers and one muscle fiber is innervated by a single motoneuron • The ensemble of muscle fibers innervated by a single neuron and corresponding motoneuron constitutes the motor unit 10 Motor unit • A typical muscle is innervated by about 100 motoneurons which are localized in motor nucleus • Each motoneuron innervate from 100 to 1000 muscle fibers and one muscle fiber is innervated by a single motoneuron • The ensemble of muscle fibers innervated by a single neuron and corresponding motoneuron constitutes the motor unit 11 Types of muscle fibers Fast fibers ➢ Performance ➢ Fast fatigue-resistant – normal performance ➢ Fast fatigable – high performance Slow fibers ➢ Endurance ➢ Fatigue resistant http://www.slideshare.net/drpsdeb/presentations 12 Types of muscle fibers Fast fibers ➢ Performance ➢ Fast fatigue-resistant – normal performance ➢ Fast fatigable – high performance Slow fibers ➢ Endurance ➢ Fatigue resistant http://www.slideshare.net/drpsdeb/presentations 13 The recruitment of motor neurons m. gastrocnemius in a cat http://www.slideshare.net/drpsdeb/presentations 14 Neuromuscular junction http://classes.midlandstech.edu/carterp/Courses/bio210/chap09/210_figure_09_11_labeled.jpg 15 Neuromuscular junction https://s3.amazonaws.com/classconnection/803/flashcards/9818803/png/initiation-151586429D6310D1C56.png 16 Muscle fibers http://www.sivabio.50webs.com/mus019.jpg 17 Types of muscle contraction • Isometric contraction ➢ Constant length • Isotonic contraction ➢ Constant tension ➢ Concentric x excentric contraction http://www.slideshare.net/drpsdeb/presentations https://i0.wp.com/colebradburn.com/wp-content/uploads/2013/02/contractions.jpg 18 Proprioception • Information about the position of body parts in relation to each other (The sum of information about lengths of particular muscles) • Information about movement (The force and speed of muscle contraction) • Reflex regulation of muscle activity • Muscle spindles – Lie in parallel with extrafusal muscle fibers • Golgi tendon organ – Arranged in series with extrafusal muscles http://www.slideshare.net/CsillaEgri/presentations 19 Muscle spindle and Golgi tendon organ http://images.persianblog.ir/559630_iXFiuRo0.jpg 20 • Nno-force generating contractile structures • The contractility is for spindle length adjustment • Encapsulated structure filled with a fluid • Intrafusal fibers – Lie in parallel with extrafusal muscle fibers (Stretch/shorten along with extrafusal fibers) – Efferent connections (into muscle spindle) • γ motoneuron – Afferent connections (from muscle spindle) • Information about change in muscle length • Reflex regulation of the α motoneuron activity http://www.slideshare.net/CsillaEgri/presentations Muscle spindles 21 Muscle spindles • Nno-force generating contractile structures • The contractility is for spindle length adjustment • Encapsulated structure filled with a fluid • Intrafusal fibers – Lie in parallel with extrafusal muscle fibers (Stretch/shorten along with extrafusal fibers) – Efferent connections (into muscle spindle) • γ motoneuron – Afferent connections (from muscle spindle) • Information about change in muscle length • Reflex regulation of the α motoneuron activity http://www.slideshare.net/CsillaEgri/presentations 22 Muscle spindle • Static fibers • Dynamic fibers • Afferent connections (from spindle) – II – static fibers • Information about muscle length (position) • Ia – static and dynamic fibers • Information about muscle length and contraction (movement) – Reflex regulation of the α motoneuron activity • Efferent connections (into spindle) – Static γ motoneurons – Dynamic γ motoneurons – Spindle length adjustment http://www.slideshare.net/CsillaEgri/presentations 23 Afferent signaling from muscle spindles II – Static fibers • Static response Ia – Static and dynamic fibers • Static and dynamic response http://www.slideshare.net/CsillaEgri/presentations 24 Efferent signaling into the muscle spindle • γ motoneurons adjust the length of intrafusla fibers • Regulation of sensitivity • α and γ coactivation • http://www.slideshare.net/CsillaEgri/presentations 25 Golgi tendon organs • Non-contractile encapsulated structures • Collagen fibers • Ia fibers • Mechanoreception • Arranged in series with extrafusal muscles • Information about changes in tendon tension/force • Reflex regulation of the α motoneuron activity http://www.slideshare.net/CsillaEgri/presentations 26 Reaction of muscle spindles and the Golgi tendon organs to muscle fiber stretch/contraction Stretch (passive) Muscle spindles reaction Contraction (active) Golgi tendon organ reaction http://www.slideshare.net/drpsdeb/presentations 27 Hierarchic organization of motor system http://www.slideshare.net/drpsdeb/presentations 28 Hierarchic organization of motor system http://www.slideshare.net/drpsdeb/presentations 29 Reflex • Reflex movement – Stereotype (predictable) – Involuntary • Proprioceptive • Exteroceptive • Monosynaptic • Polysynaptic • Monosegmental • Polysegmental http://www.slideshare.net/CsillaEgri/presentations 30 Proprioceptive reflex • Myotatic reflex – Monosynaptic – Monosegmental – Muscle spindle • Homonymous muscle - activation • Antagonist muscle - inhibition • Phasic response (Ia) – Protection against overstretch of extrafusal fibrers • Tonic response (Ia a II) – Maintains muscle tone http://www.slideshare.net/CsillaEgri/presentations 31 http://www.slideshare.net/drpsdeb/presentations 32 http://www.slideshare.net/drpsdeb/presentations 33 Proprioceptive reflex • Inverse myotatic reflex – Monosegmental – Disynaptic/polysynaptic – Golgi tendon organ • Homonymous muscle – inhibition • Antagonist muscle– activation • Protection against muscle damage caused by extensive force http://www.slideshare.net/CsillaEgri/presentations 34 http://www.slideshare.net/drpsdeb/presentations 35 Exteroceptive reflex • Polysynaptic • Polysegmental http://images.slideplayer.com/15/4638059/slides/slide_37.jpg 36 http://www.easynotecards.com/uploads/920/77/1c7a7974_150bb922c9b__8000_00004383.png 37 Hierarchic organization of motor system http://www.slideshare.net/drpsdeb/presentations 38