12 Motor system II 1 Introduction http://www.frontiersin.org/files/Articles/42416/fnhum-07-00085- HTML/image_m/fnhum-07-00085-g001.jpg http://www.slideshare.net/drpsdeb/presentations 2 Subcortical (stem) pathways controlling lower motoneurons Medial system • Axial muscle control • Tr. Vestibulospinalis – Reflex control of balance and postural control • Tr. Reticulospinalis – Muscle tone regulation (postural control) • Tr. Tectospinalis – Coordination of head and eyes movements Lateral system • Distal muscle control • „Reflex“ control of the limbs • Replaced by tr. corticospinalis • Tr. Rubrospinalis • Tr. Rubrobulbaris 3 Fixed action pattern and rhythmic movement • 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 - 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) 4 Fixed action pattern and rhythmic movement • 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) 5 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 6 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. 7 Cortical control of lower motor neuron Tractus corticospinalis Tractus corticobulbaris Voluntary motor activity 8 Voluntary motor activity Idea Association cortex Premotor + Motor cortex Basal Ganglia Lateral cerebellum Movement Intermediate Cerebellum ExecutionPlanning http://www.slideshare.net/drpsdeb/presentations 9 Voluntary motor activity • 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 10 • 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 Pyramidal tract http://images.slideplayer.com/14/4330915/slides/slide_34.jpg 11 Primary motor cortex http://www.emunix.emich.edu 12 Motor cortex • 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 13 Basal ganglia • 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 14 Basal ganglia • 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 15 Basal ganglia - inputs Corpus striatum • Connections from all cortical areas with two exceptions – primary visual and primary auditory cortex • The most of connections from – Frontal and parietal association areas – Motor areas http://www.slideshare.net/CsillaEgri/presentations 16 Basal ganglia • Motor control realized by two circuits – Direct pathway • Motor cortex activation – Indirect pathway • Motor cortex inhibition 17 Direct pathway Cortex Corpus striatum Globus pallidus internus (Gpi) Thalamus Cortex http://www.slideshare.net/drpsdeb/presentations 18 Direct pathway http://www.slideshare.net/drpsdeb/presentations • Thalamic motor nuclei activate motor cortex • Tonic inhibitions of thalamic motor nuclei by GPi • Activated corpus striatum transiently inhibits Gpi, resulting in transient disinhibition of thalamic motor nuclei 19 Direct pathway http://www.slideshare.net/drpsdeb/presentations • Thalamic motor nuclei activate motor cortex • Tonic inhibitions of thalamic motor nuclei by GPi • Activated corpus striatum transiently inhibits Gpi, resulting in transient disinhibition of thalamic motor nuclei 20 Direct pathway • Thalamic motor nuclei activate motor cortex • Tonic inhibitions of thalamic motor nuclei by GPi • Activated corpus striatum transiently inhibits Gpi, resulting in transient disinhibition of thalamic motor nuclei http://www.slideshare.net/drpsdeb/presentations 21 Indirect pathway Cortex Corpus striatum Globus pallidus externus (GPe) GPiNucleus subthalamicus (NS) http://www.slideshare.net/drpsdeb/presentations 22 • NS activates GPi • GPe tonically inhibits NS • Corpus striatum transiently inhibits GPe NS disinhibition Gpi activation Indirect pathway http://www.slideshare.net/drpsdeb/presentations 23 • NS activates GPi • GPe tonically inhibits NS • Corpus striatum transiently inhibits GPe NS disinhibition Gpi activation Indirect pathway http://www.slideshare.net/drpsdeb/presentations 24 • NS activates GPi • GPe tonically inhibits NS • Corpus striatum transiently inhibits GPe NS disinhibition Gpi activation Indirect pathway http://www.slideshare.net/drpsdeb/presentations 25 • NS activates GPi • GPe tonically inhibits NS • Corpus striatum transiently inhibits GPe NS disinhibition Gpi activation Indirect pathway http://www.slideshare.net/drpsdeb/presentations 26 Indirect pathway http://www.slideshare.net/drpsdeb/presentations • NS activates GPi • GPe tonically inhibits NS • Corpus striatum transiently inhibits GPe NS disinhibition Gpi activation 27 Indirect pathway • NS activates GPi • GPe tonically inhibits NS • Corpus striatum transiently inhibits GPe NS disinhibition Gpi activation • Less important is a direct inhibition of Gpi by GPe http://www.slideshare.net/drpsdeb/presentations 28 Direct and indirect pathway differences • Direct pathway ➢ Motor cortex activation • Indirect pathway ➢ Motor cortex inhibition http://www.slideshare.net/drpsdeb/presentations 29 Direct and indirect pathway differences • Direct pathway ➢ Motor cortex activation • Indirect pathway ➢ Motor cortex inhibition http://www.slideshare.net/drpsdeb/presentations 30 Dopaminergic projections 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 31 Dopaminergic projections • Dopaminergic projections are crucial for the function of corpus striatum • S. nigra pars compacta • Direct pathway activation ➢ D1 receptors • Indirect pathway inhibition ➢ D2 receptors http://www.slideshare.net/drpsdeb/presentations 32 Basal ganglia • 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 33 Cerebellum http://www.slideshare.net/HarshshaH103/cerebellum-its-function-and-releveance-in-psychiatry Coordination 34 Cerebellum Cerebellum plays an important role not only in the coordination of movement, but also in the "coordination" of thoughts 35