Integative Notes - Motor Neurons
Integative Notes - Motor Neurons NSC 4354
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This 4 page Class Notes was uploaded by Christine Thomas on Friday February 19, 2016. The Class Notes belongs to NSC 4354 at University of Texas at Dallas taught by Sven Kroener in Spring 2016. Since its upload, it has received 135 views. For similar materials see Integrative Neuroscience in Neuroscience at University of Texas at Dallas.
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Date Created: 02/19/16
02.17.16 – MOTOR NEURONS Forebrain Motor systems Descending systems Upper motor neurons Motor cortex Planning, initianting, voluntary movements Brainstem centers Basic movments, postural control Cortical spinal tract * Overview of descending motor control Posture and balance – midline (core muscles) Upper motor neurons cross over and travel through blue (into the spinal cord) – synapses in the lower motor neurons in lateral ventral horn Sensory – dorsal root Alpha motor neurons that control muscles Inter neurons involved Long distance curi – modulate (medial Short distance – for distal limb muscles (lateral Upper motor neurons – motor corticies PMC SMC Primarmy motor cortex Get feed back on what you are touching Tactile feed back – you can plan your movement Primary motor cortex – upper motor neurons Layer 5 – upper motor neurons Form the out put from the outside of brainstem Anywhere in cortex is output later Decending projections Broadmann – differences in thickness of layers Layer 5 is particularly thick They are distinct by the different layer they have – anatomical layers – functional areas Area 4 would be the motor cortex Characterized b really large betz cells Don’t have specific role They are primary motor cortex Some how in primates they emerged (not found in lower vertabrates) They don’t make all the projects Corticospinal and corticobulbar tracts Corticospinal tract Controls movment of torso – upper and lower limbes Corticobulbar Controls face and neck Terminates only in brainstem Pyramidal tract – they look like pyramids – caudal medulla Yellow projections – face – cortical bulber – lateral side Corticalspinal – medial side Internal capsule See it better in the thick myelinated super highway of fibers Cuts throught he basal ganglia in thalamus Where pyrimal tract Cerebral peduncle Lateral corticospinal tract Left part of brain – controls right part of body to 90% Cortocspinal tracts Desussaion – crossing in pyramids – why you have 90% of contralateral side Lateral CS – controls distal extremities Ventral Tract (aka antrerior tract) – controls proximal limbs Two pathways and crossing To sepertate they better LCST – limbs VCT – axial – trunk – proximal limbs Not just descending – local and commissural too Projection in internal capsule Projections that go to the other side – thalamus, Basil ganglia Doesn’t just control brainstem Projecctions to other areas – within cortex or two lower sub cortical structions Early studies – motor homunclulus – topographic organization Somatosensory cortex Put a large electrode in brain = came up with homunculus Had concept individual areas in brain that would control the muscles in those areas There was a motor homunculus There are neurons that control muscles more than muscle in other parts Motor homunculus with pyramidal tracts Have distinct parts where ______ travel Certain topography But what do motor maps really represent Not muscle control Muscle plan movments Classic studies – indicates maps of muscles Make muscle twitch When they used smaller stimulation – found a more complex arrangement Complex type of movement Not just muscle one to one connection but much omore transfused – more areas that control muscle movmements Divergence – a neuron on place – control alpha motor neurons Convergence – wide areas of mtor cortex can control same muscle Specific types of movement s Motor maps basted on microstimulation Outer outward movements Involve very complex patterns Remember there is a certain overlap with the muscles you need When you stimulate these muscle they _______ Directional tunin of neurons in primary cortex Tuning curves of single neuron Plack like – action potential Cell tuned to movments to a specific angle But not on other angles Individual neurons brought to be tune – wide range Broadly tuned to the left Activate large ensomals of neurons They don’t encode trajectory but also end postion of hand Premotor cortex Gets most input from prefrontal cortex Where you would plan a movement – working memory Have an indirect control and direct control of movment About 30% come directly out of cortex Rest arised from premotor cortex Direct control of movement Weaker connections Does control directly but mostly its related to motor planning and selection of movement When you learn a task – most active Motor planning Understandin the actions of others – mirror neurons Mirror neurons – neurons that encode ntention Active when animal see someone else do something They are doing the task in their head before actually doing it (plans it – putting your self in someone elses shoes) Not active when using a tool Respond when animal not actually seeing it Motor control in the brainstem: balance , posture, gaze Involuntary movments Extrapyramidal tract – involtary reflexes and movment and modulation of movment – reaching Run in extrapuramidal part of the tract –to distinguish it from the tract of motor cortex Motor control in brainstem Task – pull on lever when you hear a tone If you don’t anticipate what is going to happen then you will can pull your self into the wall But not the case – anticipation – feet forward control – posture compensates Involuntary reflex that you need (bending of knees) Happens through reticularspinal pathway – predicts distabance in stability Feedforward and feedback signals Feedforward – anticipated postural instability Postural adjustment Feedback – uunanticipated postural instability – compenstate for things that you don’t anticipate Indirect pathway control posture Reticular formation – recicular spinal – coactivated with anything that cortical spine way does They project to motor neurosn in spinal cord that controls axial and proximal muscles Tectospinal, reticulospinal and vestibuospinal pathways Tectorspinal Anferior colliculus and superior colliculus Control – head and gaze – visual input Motor control in the brainstem Use for orienting of neck Coordination path – limb and trunk movments Lateral – proximal limbs Vesibulospinal pathway Vesibular nulei th Receive input from 8 cranial nerve Rotary movments Acceleration of head Medial vesibulospinal pathway Reflex control of neck muscles What type of imput does it get (uses – vestibule nucli) Reticulospinal pathway Autonomic movments of locomotion and posture Influences muscle tone Colliculospinal pahwya Orienting head and eye movments Upper motor neurons syndrome Babinski reflex Descending control is lost Cant suppress extensor withdrawl Example of clinical testing Type of movment if it was on level of central pattern generator – fanning of toes Have control from upper motor neurons
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