Motor system Motor system2 Introduction Motor system3 • 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 system4 • 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 system5 • 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 system6 • 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 system7 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 system8 Topography http://www.slideshare.net/drpsdeb/presentations Motor unit Motor system9 • 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 system10 • 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 system11 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 system12 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 system13 http://www.slideshare.net/drpsdeb/presentations m. gastrocnemius in a cat Neuromuscular junction Motor system14 http://classes.midlandstech.edu/carterp/Courses/bio210/chap09/210_figure_09_11_labeled.jpg Neuromuscular junction Motor system15 https://s3.amazonaws.com/classconnection/803/flashcards/9818803/png/initiation-151586429D6310D1C56.png Muscle fibers Motor system16 http://www.sivabio.50webs.com/mus019.jpg Types of muscle contraction Motor system17 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 system18 • 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 spindles Motor system19 • 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 Golgi tendon organs Motor system20 • Non-contractile encapsulated structures • Collagen fibers • Ib (Aα) 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 Muscle spindle and Golgi tendon organ Motor system21 http://images.persianblog.ir/559630_iXFiuRo0.jpg Reaction of muscle spindles and the Golgi tendon organs to muscle fiber stretch/contraction Motor system22 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 system23 http://www.slideshare.net/drpsdeb/presentations Hierarchic organization of motor system Motor system24 http://www.slideshare.net/drpsdeb/presentations Reflex Motor system25 • Reflex movement – Stereotype (predictable) – Involuntary • Proprioceptive • Exteroceptive • Monosynaptic • Polysynaptic • Monosegmental • Polysegmental http://www.slideshare.net/CsillaEgri/presentations Proprioceptive reflexes Motor system26 • 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 system27 http://www.slideshare.net/drpsdeb/presentations Motor system28 http://www.slideshare.net/drpsdeb/presentations Proprioceptive reflexes Motor system29 • 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 system30 http://www.slideshare.net/drpsdeb/presentations Exteroceptive reflexes Motor system31 • Polysynaptic • Polysegmental http://images.slideplayer.com/15/4638059/slides/slide_37.jpg Exteroceptive reflexes Motor system32 • Polysynaptic • Polysegmental http://www.easynotecards.com/uploads/920/77/1c7a7974_150bb922c9b__8000_00004383.png Hierarchic organization of motor system Motor system33 http://www.slideshare.net/drpsdeb/presentations Fixed action pattern and rhythmic movement Motor system34 • Fixed action pattern (e.g. Swallowing) – Neuronal networks for complex motor activity • Central pattern generator (e.g. Walking, breathing) – Neuronal networks generating rhythmic activity – „Spontaneously repeated fixed action patterns“ – No need of feedback • Localization – Walking – brain stem, lower thoracic and upper lumbar spinal cord – Breathing – brain stem – Swallowing - medulla oblongata/brain stem • Variously expressed voluntary control – Walking (full control) – Breathing (partial control) – Swallowing (limited control) http://www.slideshare.net/drpsdeb/presentations Fixed action pattern and rhythmic movement Motor system35 Fig. 1. Neural control of locomotion. A) Increments in the intensity of stimulation of the MLR in the high decerebrate cat increased the cadence (step cycles/sec) of locomotion. Adapted from Shik et al. 1966.[22] B) Schematic of the velocity command hypothesis: a command signal specifying increasing body velocity descends from deep brain nuclei via the MLR to the spinal cord and drives the timing element of the spinal locomotor CPG to generate cycles of increasing cadence. Extensor phase durations change more than flexor phase durations. The command signal also drives the pattern formation layer to generate cyclical activation of flexor and extensor motoneurons. Loading of the activated muscles (e.g. supporting the moving body mass) is resisted by the muscles' intrinsic spring-like properties. This is equivalent to displacement feedback. Force and displacement sensed bymuscle spindle and Golgi tendon organ afferents reflexly activate motoneurons. A key role of these afferents is to adjust the timing of phase transitions, presumably by influencing or overriding the CPG timer. Adapted from Prochazka & Ellaway 2012.[23] https://en.wikipedia.org/wiki/Central_pattern_generator Fixed action pattern and rhythmic movement Motor system36 Whelan PJ. Shining light into the black box of spinal locomotor networks. Philosophical Transactions of the Royal Society of London B: Biological Sciences. 2010;365:2383–2395. Voluntary motor activity Motor system37 Idea Association cortex Premotor + Motor cortex Basal Ganglia Lateral cerebellum Movement Intermediate Cerebellum ExecutionPlanning http://www.slideshare.net/drpsdeb/presentations Voluntary motor activity Motor system38 • Result of cooperation of upper and lower motor neuron • Basal ganglia – Motor gating – initiation of wanted and inhibition of unwanted movements • Cerebellum – Movement coordination http://www.slideshare.net/drpsdeb/presentations Pyramidal tract Motor system39 • Upper motor neuron – Primary motor cortex • Lower motor neuron – Anterior horn of spinal cord • Tractus corticospinalis lateralis – 90% of fibers • Tractus corticospinalis anterior – 10% of fibers – Cervical and upper thoracic segments • Tractus corticobulbaris http://images.slideplayer.com/14/4330915/slides/slide_34.jpg Primary motor cortex Motor system40 http://www.emunix.emich.edu Motor cortex Motor system41 • Primary motor cortex (area 4) – Somatotopic organization – Control of lower motor neuron • Premotor cortex (area 6 laterally) – Preparation of strategy of movement • Sensor motor transformation • Movement patterns selection • Supplementary motor cortex (area 6 medially) – Involved in planning of complex movements • Movement of both limbs • Complex motion sequences – Activated also by complex movement rehearsal http://www.slideshare.net/CsillaEgri/presentations Basal ganglia Motor system42 • Corpus striatum – Nucleus caudatus – Putamen • Globus pallidus (Pallidum) – Externum – Internum • Nucleus subthalamicus • Substantia nigra – Pars compacta – Pars reticulata • Thalamic motor nuclei http://www.slideshare.net/CsillaEgri/presentations Direct and indirect pathway differences Motor system43 http://www.slideshare.net/drpsdeb/presentations • Direct pathway ➢ Motor cortex activation • Indirect pathway ➢ Motor cortex inhibition Dopaminergic projections Motor system44 http://www.slideshare.net/drpsdeb/presentations • Dopaminergic projections are crucial for the function of corpus striatum • S. nigra pars compacta • Direct pathway activation ➢ D1 receptors • Indirect pathway inhibition ➢ D2 receptors Basal ganglia Motor system45 • Beside motor loop there are other loops associated with other thalamic nuclei • „Gating“ of the other sort of information • Association loop • Limbic loop • Basal ganglia play an important role in information processing in general and this is crucial for thinking process • Connections of corpus striatum are plastic what allows learning and this was very important during evolution http://www.slideshare.net/CsillaEgri/presentations Cerebellum Motor system46 • Coordination • Cerebellum plays an important role not only in the coordination of movement, but also in the "coordination" of thoughts http://www.slideshare.net/HarshshaH103/cerebellum-its-function-and-releveance-in-psychiatry