Neuroanatomy Notes

  • Pyramidal System

    __Neuron 1: primary motor area __ -motor homunculus: area of cortex allocated to each part of body is proportional to importance of that area -axon passes through internal capsule into cerebral crus __Neuron 2: interneuron__ cell body locations: a.) motor nuclei of cranial nerves b.) base of dorsal horn \\*this neuron may be absent in primates --> faster transmission __Neuron 3: fusimotor neuron__ cell body locations: a.) motor nuclei of cranial nerves b.) ventral horn - usually gamma but sometimes alpha motor neuron __species variation: ungulates__ -entire pyramidal system is small and ends in cervical region -fibers decussate in pyramid but then mainly descend VCST alongside ventral fissure -small lateral CST and also a very small dorsal CST extending to C5 "},{"left":"groups of axons <


  • Extrapyramidal System

    Forebrain:\n\n1. cerebral cortex\n2. globus pallidus\n\n \n\nMidbrain:\n\n3. midbrain reticular formation\n4. red nucleus \n5. tectum\n\n \n\nHindbrain:\n\n6. pontine motor reticular centers\n7. lateral medullary motor reticular centers\n8. medial medullary motor reticular centers\n9. vestibular nuclei \n\n "},{"left":"list spinal pathways and functio


  • Extrapyramidal Feedback Circuits

    A.) feedback circuits through cerebellum: all 9 EP motor command centers -inform cerebellum of intended motor actions of EP motor centers -enable cerebellum to regulate these actions as they progress B.) feedback circuit through thalamus: basal nuclei -shorter circuit -enables basal nuclei to carry out their main role in collaborating with cerebral cortex "},{"left":"cerebe


  • Function of Extrapyramidal System

    __1. cerebral cortex - relatively restricted parts 2. basal nuclei - particularly globus pallidus 3. red nucleus 4. tectum 5. midbrain reticular formation 6. pontine motor reticular centers 7. lateral medullary motor reticular centers__ - strictly inhibitory but produce facilitation by disinhibition of the medial medullary motor reticular centers __8. vestibular nuclei __ "},{"left":"inhibitory components


  • Somatic Motor Systems

    __1. corticonuclear pathways__ -arise from primary motor area of cerebral cortex -projects to motor nuclei of cranial nerves that innervate striated muscle of the head -3 neurons, the first of which decussates __2. corticospinal pathways__ -arise from primary motor area of cerebral cortex -projects to striated muscle of body -3 neurons, the first of which decussates usually in pyramids -spinal tracts: \n\n> lateral corticospinal: principle path in humans and carnivores ventral corticospinal: main path in ungulates; confined to neck in all dorsal corticospinal: ungulates only \n\n-poorly developed system in ungulates ending anatomically in cervical spinal cord __3. feedback circuits__ primary motor area --> pontine nuclei --> cerebellum --> thalamus --> back to primary motor area \\*decussates twice: on way to and from cerebellum (cerebellum regulates contralateral cerebral cortex) \\*corticopontocerebellar pathway: constitutes first half of this feedback circuit "},{"left":"extrapyramidal system compone


  • Cerebellum - basic functions

    1. coordination and regulation of all somatic motor activity* \\*\\**cannot initiate movement\\*\\*\n1. control of posture"},{"left":"require


  • Cerebellum - afferent pathways

    __function: __transmit proprioceptive information from muscle spindles and golgi tendon organs __termination: __ipsilateral cerebellar cortex, somatotopically arranged; constitute part of __*\"mossy fibers\"*__ 1. dorsal spinocerebellar tract 2. ventral spinocerebellar tract *-double decussation * 3. cranial spinocerebellar tract 4. spinocuneocerebellar pathway "},{"left":"pyramidal feedback input


  • Cerebellum - efferent pathways

    __Neuron 1: __Purkinje cell __Neuron 2: __deep cerebellar nucleus __Neuron 3: __ \n\n> *a.) ventrolateral thalamus* \n\n> > -projects to cerebral cortex and globus pallidus -feedback pathway of EPS/PS \n\n> *b.) midbrain motor centers - EPS* \n\n> > -midbrain reticular formation -red nucleus -tectum \n\n> *c.) hindbrain motor centers - EPS* \n\n> > -pontine motor reticular centers -lateral medullary motor reticular centers -medial medullary motor reticular centers -vestibular nuclei "},{"left":"specific deep cerebellar nuclei efferent


  • Pathways in Cerebellar Peduncles

    __AFFERENT:__ 1. olivocerebellar 2. vestibulocerebellar 3. medullary reticulocerebellar 4. pontine reticulocerebellar 5. dorsal spinocerbellar 6. cranial spinocerebellar - part 7. cuneocerebellar EFFERENT: 1. cerebellovestibular 2. cerebelloreticular "},{"left":"middle cerebellar peduncle",


  • Cerebellum - anatomy/organization

    Vestibular: A.) vestibulocerebellum (archicerebellum): flocculonodular lobe Proprioceptive: B.) spinocerebellum (paleocerebellum): vermis Feedback areas: C.) pontocerebellum (neocerebellum): majority of hemispheres and midpart of vermis "},{"left":"histological layers<


  • Autonomic Nervous System: diencephalon

    \n\nautonomic nuclei ","right":"- at least 22 nuclei are named by NAV\n- two of the most important lie in the medial part of hypothalamus and include:\n\n__1. supraoptic nucleus: __immediately dorsal to optic chiasm __tract:__ supraopticohypophyseal __predominant product: __ADH __2. paraventricular nucleus:__ lies alongside third ventricle __tract:__ paraventriculohypophyseal __predominant product: __oxytocin\n\n \n\ntelencephalon connections: both belong to limbic system \n\n1. amygdaloid body\n-respiratory, circulatory, iridal, piloerector manifestations during emotional reactions \n2. septal nuclei\n-receive olfactory projections\n-appear to be concerned with sexual and aggressive behavior\n\n "},{"left":"h


  • Autonomic Nervous System: hindbrain, spinal cord

    - ill-defined neuronal pools in medullary reticular formation - primitive neurons that overlap/superimpose and have many collaterals and numerous connections\n - __cardiovascular centers: __\n - __medullary cardiovascular center: __reticular formation of medulla\n - __a.) vasomotor depressor center: __medial group of nuclei\n - __b.) vasomotor pressor center:__ lateral group of nuclei\n - __respiratory centers__\n - __medullary respiratory center:__\n - __a.) expiratory center:__ lateral group of nuclei\n - __b.) inspiratory center: __medial group of nuclei\n - __pontine respiratory center:__\n - __a.) pneumotaxic center__\n - inhibits inspiratory center by negative feedback\n - __b.) apneustic center__\n - applies steady excitatory drive on inspiratory center\n - __alimentary centers__\n - known to exist in the medulla of sheep\n - __1. ruminoreticular center__\n - __2. esophageal center__\n- autonomic pathways project downwards by means of *reticular formation of brainstem *and *reticulospinal tracts of spinal cord *\n\n "},{"left":"au


  • Cerebral Cortex: basic function/organization

    br> relative proportions ","right":"a.) archicortex: hippocampus - rhinencephalon (limbic) b.) paleocortex: piriform lobe - rhinencephalon (olfactory) c.) neocortex:: association areas and projection areas relative proportions of association areas/projection areas + rhinencephalon -0%/100% in rabbits -20%/80% in cats and dogs \n\n> association areas enable analysis of received information, comparison with past experience and elaboration of appropriate course of action -- varying manner in each an individual follows this is its distinct *personality * \n\n-85%/15% in humans "},{"left":"association ","right":"receiving items of info


  • Thalamus - functional groups of nuclei

    br>1. ventrocaudal thalamic nucleus cell station of third and final neuron of medial leminscal system 2. metathalamus medial geniculate nuclei  - third neuron of hearing lateral geniculate nuclei - third neuron of vision 3. ventrolateral thalamic nucleus entirely concerned with feedback \\*final neuron in cerebellar - pyramidal feedback pathways \\*final neuron in cerebellar - extrapyramidal feedback pathways to highest extrapyramidal motor command centers \\*feedback link between basal nuclei (globus pallidus) and extrapyramidal motor areas of cerebral cortex - enables basal nuclei to carry out their main function (collaborating with cerebral cortex) 4. projects only to lateral group of thalamic nuclei \\*forms link between medial lemniscal system (sensory information) and cognitive cortex "},{"left":"lateral group


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