Int Neuro Exam 2 Study Guide
Int Neuro Exam 2 Study Guide NSC 4354
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This 16 page Study Guide was uploaded by Christine Thomas on Saturday March 5, 2016. The Study Guide belongs to NSC 4354 at University of Texas at Dallas taught by Sven Kroener in Spring 2016. Since its upload, it has received 44 views. For similar materials see Integrative Neuroscience in Neuroscience at University of Texas at Dallas.
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Date Created: 03/05/16
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 movement if it was on level of central pattern generator – fanning of toes Have control from upper motor neurons 02.22.16 Modulation of movement by the basal ganglia Reciprocal regulatory loops Cerebellum Both of the basal ganglia and cerebellum– don’t have direct connection to lower motor neurons Modulate activity in upper motor neurons Have indirect projection into the thalamus Basal gangia – straitum (look at all the sub names) Motor components of the basal ganglia circuit Striatum Caudate nucleus Putamen Ventral striatum Nucleus accumbens Important in driving some of these a0reas What goes through the internal capsules – upper motor neurons Cuts the striatum in half Globus pallidus Internal and external segment Subthalmic nucleus SN Provides dopamergeric Motor or other corticies – not part of basal ganglia Nuclei Basic circuitry of the basal ganglia Have this loop that goes through caudate and putamen and relay nuclei and thalmus Cortex drives the whole thing – Sorta like a echo and modulates it Current thinking about functions of the basal ganglia The basal ganglia contribute to the smooth execution of sequential movments Have some neurons in BG that will change with movment Stritum signas aspects of learning and reinforcement in relation to movment Approach behavior Reinforcement part has to do with drug addiction Roles that ventral striatum initiates When it becomes more habitual – dorsal striatum takes control Associated with reward or error signal Goal directed The BG are involeved in certain kinds of produral learning and habit formation Habitual or procedural How ever: BG not just motor functions alone Have other functions too Plz sign name below Motivation that I will do this to get reward Requires higher order association cortex BG motor cortex There is also context – look their imputs that also control the basal ganglia –the actual execution of the signature Also involved in memory and emotion The striatum Dorsal striatum – caudate – putamen Below that is the central striatum or nucleus accumbes BG circuitry Both drawings of the circuitry Projection to the interior/exterior of the GP Inputs to the basal ganglia (stratum) Corticostrial pathway Goes into caudate and putamen Have different info Caudate Inputs from frontal and motor corticies – eye movment Putamen Inputs from high order sensory cortices, premotor, and motor corticeis They are parallel – so they are segretated Keeps them separated and maintained Parallel corticle representations in BG circuitory Loops Procjections go to different areas of the putamen They come back the same way from where they arrived Loops of modulation Same input Parallel cortical inputs to basal ganglia Have same organization Whole idea is that there is a functional segretation of parallel bg inputs Neurons of the caudate and putamen Projection neurons Medium spiny neurons Most abundant type of neurons Use GABA as neuro transmitter It is inhibitory – inhibit area it projects to – inhibitory net work Low level Basal activity – fairly quiet Basically don’t do much unless activated Local circuits neurons Very small number Rage of 2-3 % Inhibitory inter neurons MSN and their connections External cause it further away from midline Internal cause it is closer to the midline Both pathways from caudate to putament to external/internal arrive from the MSN They are you cortical neuron cells – excite MSN – inhibit GP or SNPR Being driven from input from the cortex Have dopagernic cells that also modulate Presynaptic from the inputs Neurotransmitters of the BG Excitory inputs come frome Frontal motor corticies Primary motor Ctx Premotor ctx Other cortices Modulatory inputs Intricnsic inhibitory porjections Intrinsic circuitry and outputs of the BG Eye movements – SNPR SC Excite GPI – inhibitory goes down (less activity) – these fire all the time – they also release GABA so they tonically inhibit the thalamus Frontal cortex stimulate caudate and putamen would cause VA and VL to have more activity – dishibition Intrinsic circuitry and disinhibition Tonically inhibit in the SC or the VA/VL thalamus – inhibit unwanted movements MSN in striatum inhibits inhibition disinhibition initation of movement Disinhibition in the BG A – MSN B – shows they are tonically active who are tonically inhhibity they thalamus © which drives the motor cortex (D) Just read the slide (the colorful part of the slide at the bottom – how neurons fire and how you get the gaps) Disinhibition in the basal ganlia SC controls eye movment Gap where the SC becomes active Using inhibitory transmittors twice Direct and indirect pathways Direct pathway For release of tonic inhibition - thalamus First time dopamergic Neurons that make up this neurons they have D1 receptors On avg get a stimulation Whole thing hinges on what you have in the SNPC – direct connection btwn other kinds of pathways Indirect Same components as before slide just an additional step in the external segment Detour in subthalamic nucleus Opposite effect of the direct pathway Through indirect pathway – another layer of modulation – having a disinhibition of excitory pathway D2 – inregulates neurons D1 - regulates neurons Always increases movement Direct and indirect pathways Direct pathway – facilitates movement Indirect pathway – inhibits movement Dopamine has a facilitatory output effect on both D1 and D2 receptors is opposite same net response Focused projection in direct pathway VS diffuse projection in indirect pathway Modulation in indirect pathway is diffused Better focus selection of things (motor movement) Might be inputs that make you do one type of movement – reach a goal – oter circumstance might not allow you to make these movements Nucleus acc – ventral striatum Outputs Diseases of basal ganglia Involved in the control of movement and affected in movement disorders Parkinson and huntington - pathological changes in subcortical nuclei Three characteristics Tremor / other involuntary movments Changes in posture and muscle tone Povery and sloness of movement without paralysis Hypokinesia – Parkinson Hyperkinesia – huntintons Catecholamines Dopamine Movement or motor disorders – parkinsons Reward or motivation – projection to VA stritum Schizophrenia Parkinsons Movment disorder Symptoms Akinesia – can walk but first step hardest Muscle rididity Tremor Bradykinesia Postural instability Treatment - repeasement of lost DA with LDOPA or DA agonist – efficacy decreases over time Parkinsons disease – loss of DA neurons Dark areas seen in the slices of brain …. EW Lots of redundancy in system Only loss of 70% show symptoms Huntingtons Has do with cell give rise to pathways Loss of GABAergic projection neurons Caudate /putamen is super etrified – losing a large proportion of cells Have a 50% chance of inheriting disease 02.24.16 – MODULATION OF MOVMENT OF THE CEREBELLUM Forebrain motor Systems Cerebellum – sensory motor coordination of ongoing movements Error correction (function) Input from cortex (spinal cord) have a signal – cortical info – integrated in a away and then modulated to send back info through the thalamus To detect the difference btwn the intended movement and the actual movement Same concept as the basil ganglia Getting input from certain areas and providing feedback to areas to regulate correct what is going on Reciprocal loop Function Cerebellum – contributes to coordination, precision and accurate timing Integrates these inputs to fine tune motor activity Damange in cerebellum doesn’t cause paralysis but causes Disorders in fine movement, equilibrium, posture and motor learning Doesn’t directly influence the spinal cord Function Maintence of balance and posture Literally keep Receives input from vestibular receptors and proprioceptors Gets ascending info from here Compensation for shifts in body position or changes in load upon muscles There fore if you have this then suffere from balance disorders and hey often sterotyped postural stratagies Ataxia Has a wide staggering gait Coordination of voluntary movements Majority function of cerebellum is coordinate timing ad force of different muscle group to produce fluid limb or body movement Has trouble to point at fine target (aka nose) Motor learning Adatptin and fine tuning motor programs to make accurate movments through a trial and error process Cognitive funtions Involved in certain cog functions – language Schmahmanns syndrome – executive functions – working memory, spatial cog and learning and effect – Organization of the cerebellum Cortex – cerebellar cortex (in gray) where most of the cells reside – where they spread – different parts of this: cerebrocerebellum, spinocerebellum, vestibulocerebellum Deep nuclei Cerebellar peduncles – fiber tracts Through which info enters and leaves Cerebrocerellum Lateral part Largest subdivision Grows in humans and primates Recives most imputs from cortex Important for skilled movments, planning and execution of spatial and temporal sequences Spinocerebellum Input from spinal cord Later – movement of distal muscles – arms, limb, fingers Medial Vestibulocerebellum Inputs from vestibular Vestibule oculo Rostro caudal division Anterior lobe – older part of cerebellum – paleocerebellum – posture and balance Posterior lobe – newest part Vestibulocerebellum – seen in the side – green part – flocculonodar lobe Folded many times – folia – to make more space – packaging things rather tightly Organization – pathways (cerebellar peduncles) Superior – efferent – out going – pure functions Middle – afferent – incoming fibers Inferior – mixed – both and reciveing and leaving fibers They go to some degree through this deep nuclei (receive one copy of inputs) into cerebellar cortex Cerebellar inputs – peduncles Too many types of info Ponti nuclei – cortical information Middle cerebellar peduncles has 20million axons in the projection – pyramidal tract only has 1 million axons Recive input from cortex and cortical input Inferior olive (mixed) Receives some frontal cortex – cortical inputs through the red nucleus Directly get spinal and brainstem inputs Ascending inputs from the dorsal nucleus clark Cerebellar inputs Areas in which contribute most to this Deep cerebellar nuclei – cerebello cortical outputs Closing loop and same areas that send inputs are Cerebellar cortex info to deep cerebellar nuclei ascending VL complex/ thalamus to superior colliculus (eye movements) Superior cerebellar peduncles – efferent (leaves the cerebellum projects to thalamus) Descending output to brainstem Go into RF and VN Regulate lower motor neurons Control of axial and proximal limb musculature posture Summary Closing the loop 1. Cortex (cerebal cortex) 2. Pontine nuclei 3. Cerebral cerebellum 4. Dentate nucleus (one of the deep cerebellar nuclei) 5. Thalamus Spinocerebellum Receive slightly different Vestigular n Functional subdivisions – summary Totally different dentate Cereberal cerebellum – dark yellow – planning movements Cerebellar cortex 3 layers Molecular – lots of fibers run Purkinje Granule – many very small neurons Cellypes in the cerebellar Purkinje – info leave into deep neucli Granule cells – very small – at least 50 billion – So small that have hard to recording the functions Make the parallel fibers Innovate the purkinje cells And different types of inhibitory neurons Cerebellum circuit diagram Two inputs Inferior olive Spinal cord projections Ascending projection Mossy fiber inputs Molecular layer and spread out about 6 mm They make contact with number of pukinje cells Pukinje lie in their own layer Pontin nuclei – cerebral cortex project there Descending projections Corticle inhibitory loop Same info but sign reversed Excite inhibitory neurons 3 fiber types contribute to arrays Mossy fiber inputs – from pontine Make parallel fibers Contacts 200 granule cells Each granule receives input from at least 5 mossy fibers each parallel fiber makes around 100 purkinje cells climbing fiber inputs only makes contact with a single purkinje cell have a very strong direct input cerebellar cortex connectivity deep excitary loop make direct contact with deep nuclei produce cortical loop drive inhibitory neurons – purkinje climbing fiber – training signal carry info from – spinal provide motor error signal to cerebellum important for motor timing relevant for short term adaptation and long term motor learning error control difference in inputs parallel fibers evoke single/ simple spikes climbing fiber evoke complex spikes Modulation of ongoing movments Muscle movements (flick of wrist) Purkinje cells Deep cerebellar cells Motor learning – vesibulo ocular reflex When you rotate head your eyes fix on something VOR gain reset – compensate the change 02.29.16 – VISCERAL OR ANS Types of motor organs Muscles Smooth Striated Cardiac – heart Skeletal Trunk Limbs and digits Head and nck Major diff btwn somatic (skeletal) muscle system and autonomic (visceral) motor system Lower motor neurons of ANS Located outside CNS – autonomic ganglia Pre ganglionic glands – sit in spinal cord Contacts btwn visceral motor neurons and targe organs are less differentiated Signal transmitter Volume transitter Hypothalamus and regions in brain stem Control skeletal muscles Other areas – basal ganglia – motor and pre motor cortex Variability of neurotransmitter used Postsynaptic higher – more degrees of freedom in regulating homeostatic/ autonomic functions Lots of different types of receptors Autonomic nevous system Innervates all effector organs and tissues except for skeletal muscles Two branches of autonomic nerous stem s Sympathetic Fight or flight Excitement and physical activity Diviation when you need to flee or fight parasympathetic Most active during rest Digenstive activities stimulated Reduces energy normally Two branches of the ANS Sympathic Uses energy Uses NE and Ach as neurotransmitter 4 F responses – fight, flight, fright, F*** Parasympathetic Produces energy Autonomic nervous sytem Work together to deal with homeostasis Control a constant internal state Have to expand energy to produce energy Short term effects may deviate from set points Long term – you are trying to maintain homeostasis Contextual info – control hypothalamus (hunger and thirst) - sensory inputs (all things that regulate hunger and thirst – am I really hungry or thirsty) = what would be the antiquate thing to do regulates the bodies behavior Uses these inputs (and internal info) Allostasis Motor PNS VS ANS Somatic motor neuron Regulates skeletal muscle Autonomic ganglion – regulate the muscles Sympathetic VS parasympathetic Sympathetic neurons They are NT1 – L2 Dilates pupils Inhibit silva production Accelerates heart Gives you more energy for external threats Parasympathetic neurons Split up in several areas Slows heart Stimulates digestion Opposing functions to sympathetic neurons Sympathetic divisions of ANS Flight or fight Dilate pupils – more light – see better Blood vessels in skin and gut restric Hair come up – fearsome appearance Bronchi dilate – better oxygenation Digestion is stopped – to keep more energy Sympathetic division of ANS Innervaes muscles and skin – sympathetic ganglia Parasympathetic division of ANS Rest and digest Incuding sexual arousal an SLUDD Cervical – Sensory feedback within the ANS Not coming back from skin but rather inside the intestines Normal transmission of constriction there – blood vessels – can feel your stomach (when bloated) go into nucleus in the solidtary tract Go into the second order neurons in the spinal cord anterolateral system Hypothalamus and brainstem regulate ANS Receive input from nucleus of the solitary tact Fear or embarrassment Regulates the whole host of things Separate nuclei Controls reticular formation in brain stem Hypothalamus sits under thalamus Control by nuclei in the hypothalamus Hypothalamus regulates Blood flow Energy Metabolism Reproductive activity Response to threatening situations Sleeping and waking Paraventricular nuc – sits toward the midline – near ventricle s Project to the brain stem anadn pre ganglion neuron Nuclei that control the oxygen – Neurotransmission in the ANS Division Different types of neuro transmitter Sypathtic – uses acetycholine and then NE Releases NE to smooth muscles and cardiac muscles Para – uses only acetylcholine Releases only acetylcholine Caridic Vagus nerve – slows heart rate- uses Ach Accelerator – speeds up heart rate – uses NE Cardiac muscle regulation by the brain
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