11 Motor system I Motor system I2 Introduction Motor system I3 • 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 Introduction Motor system I4 • 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 Introduction Motor system I5 • 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 Introduction Motor system I6 • 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 Introduction Motor system I7 • 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 Lower motor neuron Motor system I8 http://epomedicine.com/wp-content/uploads/2016/07/gamma-loop.jpg • 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 Lower motor neuron Motor system I9 Topography http://www.slideshare.net/drpsdeb/presentations Motor unit Motor system I10 • 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 http://www.slideshare.net/drpsdeb/presentations Motor unit Motor system I11 • 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 http://www.slideshare.net/drpsdeb/presentations Motor unit Motor system I12 • 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 http://www.slideshare.net/drpsdeb/presentations Types of muscle fibers Motor system I13 http://www.slideshare.net/drpsdeb/presentations Fast fibers ➢ Performance ➢ Fast fatigue-resistant – normal performance ➢ Fast fatigable – high performance Slow fibers ➢ Endurance ➢ Fatigue resistant Types of muscle fibers Motor system I14 http://www.slideshare.net/drpsdeb/presentations Fast fibers ➢ Performance ➢ Fast fatigue-resistant – normal performance ➢ Fast fatigable – high performance Slow fibers ➢ Endurance ➢ Fatigue resistant The recruitment of motor neurons Motor system I15 http://www.slideshare.net/drpsdeb/presentations m. gastrocnemius in a cat Neuromuscular junction Motor system I16 http://classes.midlandstech.edu/carterp/Courses/bio210/chap09/210_figure_09_11_labeled.jpg Neuromuscular junction Motor system I17 https://s3.amazonaws.com/classconnection/803/flashcards/9818803/png/initiation-151586429D6310D1C56.png Muscle fibers Motor system I18 http://www.sivabio.50webs.com/mus019.jpg Types of muscle contraction Motor system I19 http://www.slideshare.net/drpsdeb/presentations • Isotonic contraction ➢ Constant tension ➢ Concentric x excentric contraction • Isometric contraction ➢ Constant length https://i0.wp.com/colebradburn.com/wp-content/uploads/2013/02/contractions.jpg Proprioception Motor system I20 • 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 Muscle spindle and Golgi tendon organ Motor system I21 http://images.persianblog.ir/559630_iXFiuRo0.jpg Muscle spindles Motor system I22 • 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 Motor system I23 • 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 Motor system I24 • 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 Afferent signaling from muscle spindles Motor system I25 II – Static fibers • Static response Ia – Static and dynamic fibers • Static and dynamic response http://www.slideshare.net/CsillaEgri/presentations Efferent signaling into the muscle spindle Motor system I26 • γ motoneurons adjust the length of intrafusla fibers • Regulation of sensitivity • α and γ coactivation http://www.slideshare.net/CsillaEgri/presentations Golgi tendon organs Motor system I27 • 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 Reaction of muscle spindles and the Golgi tendon organs to muscle fiber stretch/contraction Motor system I28 http://www.slideshare.net/drpsdeb/presentations http://www.slideshare.net/drpsdeb/presentations Stretch (passive) Muscle spindles reaction Contraction (active) Golgi tendon organ reaction Hierarchic organization of motor system Motor system I29 http://www.slideshare.net/drpsdeb/presentations Hierarchic organization of motor system Motor system I30 http://www.slideshare.net/drpsdeb/presentations Reflex Motor system I31 • Reflex movement – Stereotype (predictable) – Involuntary • Proprioceptive • Exteroceptive • Monosynaptic • Polysynaptic • Monosegmental • Polysegmental http://www.slideshare.net/CsillaEgri/presentations Proprioceptive reflexes Motor system I32 • 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 Motor system I33 http://www.slideshare.net/drpsdeb/presentations Motor system I34 http://www.slideshare.net/drpsdeb/presentations Proprioceptive reflexes Motor system I35 • 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 Motor system I36 http://www.slideshare.net/drpsdeb/presentations Exteroceptive reflexes Motor system I37 • Polysynaptic • Polysegmental http://images.slideplayer.com/15/4638059/slides/slide_37.jpg Exteroceptive reflexes Motor system I38 • Polysynaptic • Polysegmental http://www.easynotecards.com/uploads/920/77/1c7a7974_150bb922c9b__8000_00004383.png Hierarchic organization of motor system Motor system I39 http://www.slideshare.net/drpsdeb/presentations 79. Upper and lower motor neuron, neuromuscular junction, muscle contraction Motor system I40 • Upper and lower motor neuron localization and function • Lower motor neuron • Only the structure responsible for muscle contraction • Part of local reflex circuit • Overview of structures and main pathways controlling lower motor neuron (protprioception, higher leves of CNS including upper motor neuron, medial system, lateral system tr. corticospinalis, sorticobulbaris…) • Types of lower motor neurons (alpha, gamma, beta) • Upper motor neuron • Primary motor cortex, homunculus • Motor unit definition • Neuromuscular junction descrition • Muscle contraction description 80. Hierarchic organization of motor system – reflex vs. voluntary motor activity Motor system I41 • Hierarchy of movement • Reflex – economical, uniform, protective, fast • Rhytmic – economical solution for complex uniform actions (breathing, walking…) • Voluntary – non-economical, unique, relatively slow • Classification and description of reflexes • Fixed action pattern and rhythmic movement (definition and examples) • Voluntary motor control • Overview of structures involved in planning and execution of voluntary motor activity • Motor cortex organization (primary, premotor and supplementray motro cortex…) • Brief description of pyramidal tract