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Lectures 4-7

by: Alexis Gray

Lectures 4-7 NROSCI 1011

Alexis Gray
GPA 3.7
Functional Neuroanatomy
Susan Sesack

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Hey guys, I've taken the Lecture outlines provided by Professor Sesack and added notes from in class discussions. These notes are in PDF format. The stickies I've added can be viewed by enabling "h...
Functional Neuroanatomy
Susan Sesack
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This 28 page Class Notes was uploaded by Alexis Gray on Monday September 14, 2015. The Class Notes belongs to NROSCI 1011 at University of Pittsburgh taught by Susan Sesack in Summer 2015. Since its upload, it has received 47 views. For similar materials see Functional Neuroanatomy in Neuroscience at University of Pittsburgh.

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Date Created: 09/14/15
Functional Neuroanatomy NROSCI 1011 Gross Structure Spinal Cord Dorsal Rostral Caudal Ventral Orientation in the Nervous System There are several important anatomical terms denoting 7 r position and orientation They are simple for quadrupeds whose nervous systems have a straight longitudinal axis Dorsal Back Up Superior Ventral Belly Down Inferior PM W Rostral Nose In front Anterior 39 Caudal Tail Behind Posterior anteriOr posterior For humans persistence of the cephalic exure gives the nervous system a bent longitudinal axis with quot v 39 the spinal cord and brainstem lying along a anterior postcri or inferior different part of the axis from higher brain centers Dorsal Structures above the midbrain are horizontal to the ground 53121111 Caudal structures below the midbrain are perpendicular to the ground Rostra39 mm i I s f 1 Ventral Above the midbrain Below the midbrain quot 39 Anterior rostral ventral infgriorl Posterior caudal dorsal Arrows I Superior dorsal rostral are ShlftS 90dg to left Inferior ventral caudal coronal Xi gi r 533212110 planes A Horizontal H Caudal Planes for Viewing the Nervous System The nervous system can be sectioned in different perpendicular planes A horizontal plane is parallel to the longitudinal axis of the nervous system and cuts from side to side and front to back In the brain it is horizontal to ground in the spinal cord it is vertical to ground A coronal plane is perpendicular to the longitudinal axis of the nervous system and cuts from side to side and top to bottom In the brain it is vertical to ground in the spinal cord it is horizontal to ground A sagittal plane L sagitta arrow is parallel to the longitudinal axis and the midline of the nervous system It cuts from top to bottom and front to back A midsagittal section divides the brain into two hemispheres Anything lateral to the midline is parasagittal General Features of the Spinal Cord Neuronal migration during development of the spinal cord leads to an inner core of gray matter former mantle zone surrounded by an outer layer of White matter former marginal zone containing the axons of cells projecting out ie motor neurons or projecting in ie sensory neurons The sulcus limitans divides Ependymal zone Dorsal horn the spmal cord mto adorsal Dorsalfumculus Lateramniculus Sulcus limitans Alar plate sensory alar plate and a ventral motor basal plate This division persists in the adult gray matter Which is H shaped and has columns With dorsal and ventral halves a sensory Mantle zone Basal plate 39 Marginal zone Ventral funiculus Ventral horn Lateral horn l5 der1ved from the alar plate a Dorsal ramus Dorsal root Dorsal root Gray ramus ganglion communicans anterior horn derived from the basal plate The centrally directed axons of the sensory neurons make up the dorsal roots and terminate in the dorsal horn the soma of sensory Ventrammus spinal Ventralroot wmteragnus neurons are clustered in the communicans Fi 2 2 Develo ment of the Spinal Cord dorsal rOOt gangha AgThe walls of he neural tube rapidly increase in To Prtvmeb a thickness through cell proliferation Sulcus limitans in ganghon dicates the boundary between the basal and alar plates I l B The basal plates develop into ventral and lateral l V MOtOr neurons haVe thelr horns whereas the alar plates form the dorsal horns S m thtec soma 1n the ventral horn 1 trinfgangnon l l and their axons 1n the ventral roots A spinal nerve contains the peripherally directed axons of sensory and motor neurons and is formed by the merger of dorsal and ventral roots just as they exit the spinal column through the IE intervertebral foramen L fora to pierce The major branches rami L ramus branch of the spinal nerves contain both sensory and motor bers The thinner dorsal ramus innervates structures along the back or dorsal surface the thicker ventral ramus innervates structures on the front or ventral surface The thoracic and upper lumbar ie trunk regions of the cord contain a small intermediate lateral horn that contains the cell bodies of preganglionic motor neurons of the autonomic nervous system Their axons exit the ventral roots travel through spinal nerves and synapse on postganglionic motor neurons that innervate the smooth muscles of internal organs There are 31 pairs of spinal nerves each originating from a single 2 6 spinal segment and named for the vertebrae from which they 3 g emerge cervical neck Cl8 thoracic breast plate Tl12 cmmh 4 I lumbar loin LlS sacral sacred bone 815 and coccygeal ewes cuckoo s beak CXl 7 The dorsal and ventral roots extend the length of the spinal column 2 The spinal cord itself ends between the LlL2 vertebrae because of j l the more rapid growth of the vertebral column vs the spinal cord 2 during development In lower parts of the spinal column gholracic individual spinal cord segments lie well above the vertebrae where was 9 their dorsal and ventral roots eXit The dorsal and ventral roots that m exit the spinal column at lower levels stretch to form the cauda Termination oi spinal cord Cauda aquina amp equina surrounded by the cerebrospinal uid lled lumbar cistern This is the region from which spinal taps are drawnIn the newborn the lumbar cistern lies below the L3L4 vertebrae 3a Lumbar nerves Spinal cord 1st lumbar vertebra FIGURE 216 Cerebrospinal fluid is drawn from the lumbar cistern in a spinal tap Adapted from House Pansky and Siegel 1979 A The needle is inserted into the subarachnoid space ofthe lumbar cistern B Because the spinal cord ends rostral to the insertion point of the needle it remains undamaged during the spinal tap In this drawing of the caudal portion of the vertebral column and spinal cord the meninges have been omitted to better show the spinal rootlets in Pia mate the lumbar cistern over slpinal cord HQ Dura mater j Arachnoid j mater Dorsal root Q 4 ganglion D cistern FIGURE 215 The vertebral column grows longer than the spinal cord A side view and the detailed organization of the lumbrosacral spinal cord and vertebral column are shown at three stages of development Adapted from Pansky 1982 A Fetus at 3 months B Fetus at the end of 5 months C Newborn Cytoarchitecture of the Spinal Cord The composition cytoarchitecture of the spinal cord gray matter varies at different levels segments Neurons with similar size shape and function are clustered into longitudinal columns of gray matter that appear like layers in the coronal plane These Rexed39s laminae are the equivalent of spinal cord nuclei Layers I VI lie in the dorsal horn Neurons here process and relay sensory information Layers VIII and IX of the ventral horn contain somatic motor neurons Layer VII represents the intermediate lateral horn and contains preganglionic autonomic motor neurons Layer X surrounds the central canal Dorsal column The outer white matter contains myelinated axons that transmit information between the spinal cord and higher centers and 333 between different spinal segments These white matter bundles run the length of the spinal cord and are called columns funiculi the largest are subdivided into fasciculi They also form tracts named for Ventral column their points of origin and termination I VI Dorsal horn VII Intermediate zone VIII IX Ventral horn descending 7 The amount of White matter increases at upper levels of the quot cord ascending I The number of myelinated fibers ascending the cord he an carrying sensory information to higher brain centersbecomes greater at higher levels The number of myelinated fibers descending the cord ie carrying motor commands from higher centers becomes smaller at lower levels Hence the proportion of white to gray matter is higher at cervical levels than at sacral levels of the spinal cord The amount of gray matter increases at the cervical and lumbar enlargements The relative volume of gray matter also changes In both cervical and lumbar divisions of the spinal cord the gray matter bulges outward Lower cervical segments supply sensory and motor innervation to the arms while the lumbar segments supply the legs Thus where there are extremities there is more gray matter especially in the ventral horn In the thoracic and uppermost lumbar segments of the cord there are visible intermediate lateral horns containing the preganglionic motor neurons of the Cewica autonomic nervous system The lateral horns are most visible in thoracic segments because the ventral horns are quite small here Cervical 4 Cervical cord l l Individual spinal cord sections can be recognized as follows cervical largest size largest proportion of white matter large amount of gray matter for arms Thoracic 2 thoracic intermediate size intermediate Lateral hem high proportion of white matter very small gray matter especially the ventral horns prominent lateral horns lumbar intermediate size intermediate low proportion of white matter large igigrrgiizli39column amount of gray matter for legs sacral smallest size smallest proportion of white matter intermediate amount of gray matter Cervical 78 Thoracic cord Ventral horn Lumbar cord i Sacral cord Filum terminale 1 G Thoracic 12 Clarke39s nucleus Lumbar 5 Sacral 3 Sacral 4 Functional Neuroanatomy NROSCI 1011 Neuroembryology Urge and urge and urge Always the procreant urge 0f the world Out of the dimness opposite equals advance Always substance and increase always sex Always a knit of identity always distinction Always a breed of life Walt Whitman Leaves of Grass Zona pellucida General Features of Neural Development An egg is released by the ovary during Uterus ovulation and is fertilized by sperm in the fallopian tubes 2cell stage First cleavage Oviduct 39 OOOO39 a is formed day 5 that implants into the uterine wall The dividing cells reposition 39 and become unequal gastrulation Which a marks the beginning of differentiation Cells in the zygote divide until a blastocyst 39 Early stage of implantation whereby cells become fated to different tissue types BLASTUE H ST POI L t The outer cells become the placenta The Sigig 39 O inner cell mass becomes the embryo and TU IiP D tEm 513m EB FEM fetus Stem cells before the blastocyst are WESTE aquot l I gal totipotent and can become any tissue in O OO the body Stem cells of the inner cell Embaryqniemm cell mass are pluripotent and can become ES mm any tissue except the placenta 1 39 Skin Spina39m rdv Tailends 7 l OO O Chur lgnlc VII CHE PNS Heme LIVEr 3km Elli Amniotic fluid i Stalk H Muiliipeient stem cells Digestive I tract quot Heart 39 u O O O Ch ri ni Some blastocyst cells invaginate caus1ng three distinct germ layers to form in the embryo The E ectoderm outer becomes the skin and nervous system The mesoderm middle becomes the body a OOOOEOOOOOOOOOOOOEOOOO structure ie skeleton muscle and connective tissue and ehdoderm inner becomes the internal organs y m Ectoderma a Mesoderm The head process in the early ectoderm is induced to thicken by the notochord in the underlying mesoderm The thickened ectoderm forms the neural plate Which starts to role up and is surrounded by the neural folds Through the process of neurulation these structures become respectively the neural tube early CNS and neural crest early PNS Neurulation begins With the thickening of the neural plate and ends With the closure of the neural tube at the HCUI OPOI CS V The formation of the neural tube creates a midline aXis the neural groove Structures close to this are considered media in position While structures further away are lateral A Leaner NEURUUL Neural plate Neural fold Cross Longitudinal section section x Neural plate Di 7 7 FFF Notoehoro x Mesooerrn Endnderm Ectooerm Neural lolel Neural crest Neuralcresteells v Motoehoro Neural tune Migrating neural crest Figure 1316 Neurulation Formation of the Future Newous Sys tem a to The events of neurulation or neural tube torrnation quot are easier to envision by considering the upper suhaee at an Neural tube embryo out in half to u The neural plate on the embryos dorsal sur iaee rolls inward forming first a neural crest and then a fused neural tube E Neurulation creates a thicker anterior or cephalic head end Which Will become the brain and a thinner posterior or tail end that Will become the spinal cord The neural tube remains open at these neuropores for several weeks The anterior neuropore then closes at 24 days While the posterior neuropore closes at 26 days After fertilization Neural tube defects Failure of the neural tube to close at the anterior neuropore causes anencephaly an no la enkephalos brain Gr Failure of the neural tube to close at the posterior neuropore causes spina bifida Adjacent to the developing neural tube are segmented collections of tmesodermal cell called somites They Will make up the skeleton muscles and connective tissue and each somite Will eventually develop connections With individual spinal cord segments This segmented organization of the PNS re ects our evolution from simpler segmented organisms Neural plate Ectoderm Neural groove Neural tube Neural crest Spinal cord white matter Spinal cord Central canal gray matterxf Iquot Brain Spinal cord Features of the Neural Tube and Neural Crest Cells of the neural crest give rise to sensory neurons of the PNS and postganglionic autonomic motor neurons They also give rise to Schwann cells and meningeal cells Cells of the neural tube give rise to somatic motor neurons preganglionic autonomic motor neurons and all interneurons They also give rise to astrocytes and Oligodendrocytes Cells from the neural crest give rise to the PNS Cells from the neural tube gives rise to the CNS Multipolar postganglionic motor neurons of ANS Pia mater cells Bipolar sensory neurons AraChnold cells Chromaffin cells of adrenal medulla Schwann cells Neural Crest Pseudounipolar sensory neurons Neu rat Tu 39 Somatic skeletaI Motor neurons Multipolar preganglionic motor neurons of ANS Oligodendrocytes Astrocytes Interneurons functioning in motor control All other interneurons Interneurons functioning in sensory processing Neuronal Outgrowth Migrating Neurons develop from the neuroepithelium in the ependymal layer lining the central canal of the neural tube Migrating neurons are guided to their appropriate positions by the fibers of radial glial cells When their job is done the radial glia will differentiate intoastrocytes NEURON MIGRATION A cross sectional view of the occipital lobe which processes vision of a threemonthold monkey fetus brain center shows immature neurons migrating along glial bers from the inner to the outer surface These neurons make transient connections with other neurons before reaching their destination A single migrating neuron shown about 2500 times its actual size right uses a glial ber as a guiding scaffold To move it needs adhesion molecules which recognize the pathway and contractile proteins to propel it along Radial glial fibers Outer surface Migrating neuron Migratin w zona 39 Inner surface Farthest out The early neural tube consists of three layers or zones the ependymal mantle and marginal zones In the spinal cord neuronal migration ends in the mantle layer which will become gray matter in the adult Cells that will become motor neurons will send their axons out through the marginal layer Cells that will become sensory neurons whose soma lie outside the cord E will send their axons through the marginal layer into the mantle layer Hence in the spinal cord white matter marginal layer develops external to gray matter mantle layer In the brain neuronal migration continues into the marginal layer In the cerebellar and cerebral cortices migrating neurons form additional sublayers within the marginal zone The inner part of the marginal layer contains the descending axons of these cells and will become white matter The gray matter develops external to white matter exactly opposite to the spinal cord E B CORD QR Migrating neuroblasts MEDULLA 7 area quot 3 a a 5 a g r Zr y yew a a emit a F za 39 o a 0quot 63 pixvr egg a bug 523 V Central canal and lts 43 57 n 453 39 r aetiT af u 2 1 ut t ezz rz J Ependymal Mantle zone Marginal zone zone gray matter white matter Pia mater J External limiting Pial membrane cell Developing neural tube Migrating A neurohiast Mi ratin neuroblasts C CEREBELLUM g g 7 7 macr 5 36363 eve 355 1 9 7 4e 7 Ef e 55 raggegae 4 33 r r 333 ne er11 39 i V i 3945 T 1 39 i 391 7 I Ependymal Mantle Future Granular Ependymal Mantle Marginal zone zone white and Golgi a zone Zone zone matter cell layer l39 Internal limiting d N 39 membran quot y E I Pia mater e cell layer Molecular Purkin layer D CEREBRUM Migrating neuroblasts Margmal zone 7139 3963 ea f a awn x was quot39Q iia i 39 3 Gaga a on 4 H a ml H H I quotau39 All Pia mater o39 a a c9 gig 36 t 7 hquot 0 lt59 Q e t r Ependymal Mantle Future E 3 zone zone White E 395 7 e x u matter 5 g 3 a 39E 5 Q gt A u E E x 7 i Marginal zone FIGURE 16 Differentiation of the walls of the neural tube A Section of 5week human neural tube showing three zones ependymal mantle marginal B Section of 3month spinal cord and medulla showing retention of the original tripartite organization CD Sections of 3month cerebellum and cerebrum showing modi cation of tripartite structure caused by the migration of neuroblasts to speci c regions of the marginal zone After Crelin 1974 A Three vesicle stage B Fivevesicle stage Telencephalon Prosencephalon Lateral VentrICie Diencephalon Forebrain Mesencephalon Neural retina Rhombencephalon 0 Lens Mesencephalon gtMidbrain Third ventricle mldbram Cerebral aqueduct Metencephalon pons and I Caudal neural tube cerebellum Hmdbra39n Fourth ventricle Myelencephalon medulla Spinal cord Central canal C P onUne Ce hailC egure exure Cervrcal Cephalic Cervrcal flexure flexure tlexure Figure 522 Successive stages in the development of the neural tube A Threevesicle stage At early stages of development only early structures and the mature nervous system are summa three brain vesicles are present rized in Table 52 1 B Five vesicle stage At later stages two additional vesicles C The positions of the cephalic pontine and cervical flexures form one in the area of the forebrain 1a and lb and the other in the hindbrain 3a and 3b The relationships between these Within the developing vesicles are cavities that Will become the ventricles that circulate cerebrospinal uid lateral telencephalon third diencephalon cerebral aqueduct mesencephalon fourth met and myelencephalon central canal spinal cord The embryo develops in a curved position With three bends or exures cervical between the hindbrain and spinal cord cephalic between the midbrain and hindbrain and Wwithin the hindbrain Only the cephalic exure persists in the adult brain causing it to have a curved longitudinal axis The basal plate is the source of motor neurons After the mesencephalon there are no more motor neurons and thus the basal plate ends The sulcus limitans divides alar and basal plates Where the basal plate ends the sulcus limitans ends A shallower groove the hypothalamic sulcus lies within the di and telencephalon and divides dorsal structures with sensory function from ventral structures with motor function alar plate metencephalon By 3 months the telencephalon starts to grow more than the other vesicles eventually mesencephalon E surrounding them in a backwards twisted C shape The ventricles undergo expansion and elaboration with the rest of the structures diencephalon To increase surface area and fit more cells the sulcus limitans myelencephalon Hypothalamic sulcus O asal plate cortex folds in on itself producing many 39 fund39bu39um Basal plate ends at the convolutions and a nearly adultlike pattern mesencephalon and at birth te39encepha39on diencephalon junction Excessive alcohol consumption during the 25 days 40 days 50 days 100 days later phases of encephalization leads to microcephaly and mental retardation which characterizes fetal alcohol syndrome Cells that have already migrated to their adult positions continue to develop through the growth of dendrites axons and synaptic connections These processes continue until puberty when synapses begin to decline through a process known as pruning 5 months 6 months 7 months 8 months 9 months 7 Motor libers WW Sensory fibers I ll Oculomctor all eye muscles except those below Also clliary iris sulphllncterl sg Olfactory t W T rochlear Superior oblique Motor to W muscles of mastication Abducens Lateral rectus V Trlgemlnlal Sensory to face sinuses teetlh etc Nervus intermedius lMotor submaxllIary sublingual lacrllmal glands Sensoryanterior 3 ol tongue soft palate Muscles of lace Wimmemwmmmmimmea Vlll Vestibulocochlear Cochlear Vestibular amps Wye ma rwrmmmw w WWW I j RWWEWW 39 IX Glossopharyngeal Sensory oosterior ll of tongue tonsil pharynx middle ear g 39 a team lt lotor stylopharyngeus pharyn s mam geal musculature 3 Wmmmm t as 3 X Vague lMotorgpharynx heart lungs bronchi GI tract Sensorygheart lungs bronchi tracltea larynx Xll Hypoglossal Accessory A pharynx GI tract Tongue Sternocleido 39 external ear rnuscles mastoid trapezius a Rt 329 E Strap muscles 15 BE Erma visceral mam Somali Hea NUTIIEIT Film I uhtm39 Enemy Emory Enemy Funjinn El WE WA ml min hminslem new I swell Em II it Mme an for Ian39s amunnuda m am mp d la un for quot ITIJEE JE Eur Brewing quot sma basersow from late fur mumnt ITIJEE JE for au al mann quot lacri ma on anti saliu a on 3 rate WI b anm w m quotMEEIE for swallowing quot s iw on macaw sensory mm d bodyla39nm 1 late push or ITIJEEIE innquot swallowing mt sprawling 7 quot Eurasia art althinal mascara macaw sensory Waddlequotme r for had and mannerme quotNew bu momma GleamWee wags media for E S m ll efferent ME humeral e aerll ma zuisreral a erml 35 SUFT IHlC tment Special Visceral efferents SVE are skeletal motor neurons innervating muscles of the face mouth larynx and pharynx These muscles do not develop from mesodermal somites but from the branchial arches ie primitive gill slits that had a visceral function but became more cartilaginous in the course Maxillary process Meckel39s cartilage Squamosal temporal Pharyngeal Cleft Nasal Archl IV Auditory of evolution Hence the motor neurons innervating these muscles are called SVE For simplicity we will characterize them as SE somatic efferents Zygomatic Arch 11 Cardiac bulge Manna Mandible The optic nerve contains the axons of sensory neurons derived from the neural tube It emerges from the E diencephalon and connects to the retina The other cranial sensory neurons are derived from the neural crest and the cranial motor neurons are derived from the basal plate of the neural tube Diurnal mu ganglrrsnn Marginal I For cranial nerves with motor functions the motor neurons have their cell bodies in brainstem cranial nerve nuclei that resemble the ventral horn of the spinal cord The sensory neurons have their cell bodies in cranial ganglia peripheral to the brain They terminate in brainstem nuclei that resemble the dorsal horn Brainstem interneurons relay sensory information to higher centers and also form parts of re ex arcs ascending Afferent projections sensory cranial a ll nerve KT nucleus cranial ganglion Efferent motor cranial gquot nerve nucleus Cranial nerve nuclei are stretched out over long columns within the brainstem The smaller Ejgtgjg m t ha39 the cranial nerve number the closer its Oculomoto nucleus is to the diencephalon the larger the 399 IN39 quotquot number the closer the nucleus is to the IL DC fQLBSaIN M spinal cord You need to know the relative and not the exact rostral to caudal location IVIesencephaIic trigeminal nucleus N V Trigeminal motor nucleus N V Principal sensory rigeminal nucleus N V In the developing neural tube neurons Abducensnucleusmv mediating Vlsceral functions lie closest to Facial motor nucleusNVI the sulcus limitans neurons prov1d1ng somatic functions lie furthest from the sulcus limitans l5 Salivatory Superior NVII Vestibular nuclei N VIII Cochlear nucleus N VIII nucleus Inferior N IX Nucleus ambiguus N IX X somatic visceral visceral SO II I IEII mm iP ICIIe Hypoglossal nucleus N XII Solitary nucleus Dorsal motor nucleus N VII IX X ofvagus N X Basal plate Accessory nucleus N XI Spinal trigeminal nucleus V VII IX X Motor Sensory Sulcus limitons During development the top and bottom of the neural tube form the Mirem roof plate and the floor plate respectively Ultimately the ventricles enlarge the roof plate thins out and the oor plate Efferent thickens This causes alar plate structures to shift laterally and S 7 l5 basal plate structures to shift dorsomedially Their positions in the cmotic were Visceral efferem brainstem create columns of cells that become the brainstem cranial I Visceral afferent HCI39VC 11110161 Somatic afferent If the brainstem were collapsed like an accordion into a single coronal section the medial to lateral location of cranial nerve nuclei columns would be as shown You do need to know these medial to lateral positions Visceral efferent Spectral Afferent Motor Somatic Visceral 7 V Visceral Somatic somal39c i i afferent VIII Somatic quot afferent IV Visceral afferent Sulcus VII IX X limitans in r Visceral motor III VII IX X Special Visceral motor V VII IX X XI Somatic motor III IV VI XII Other Maior Brainstem Structures Division Structure Description White matter gray matter Medulla pyramids carry descending motor information from cortex to spinal cord corticospinal E dorsal carry ascending somatosensory columns information from spinal cord to dorsal column nuclei medial carries ascending somatosensory lemniscus information from dorsal column nuclei to thalamus dorsal column nuclei relay somatosensory information from spinal cord to thalamus inferior olivary relays sensory information multiple nucleus sources to cerebellum Pons cerebellar carry information ascending or E peduncles descending to from cerebellum pontine nucleus relays information from cortex to cerebellum Midbrain cerebral carries descending motor information peduncle L from cortex to spinal cord corticospinal little foot 39 pedestal inferior colliculus L little hill E superior colliculus tectum L roof red nucleus substantia nigra relays auditory information from brainstem to thalamus relays visual and other sensory information to motor neurons of eyes head and neck for orienting responses Reflexes relays motor information from cortex to spinal cord not corticospinal motor control region of the basal ganglia Also visible along the ventral surface at the mesencephalicdiencephalic junction are the mammillary bodies which form part of the hypothalamus and bers of the optic nerve which cross at the optic chiasm L X to form the optic tract E Also visible along the dorsal surface underneath the cerebellum is the 4th ventricle that circulates CSF Between the pons and cerebellum Within coronal sections of the brainstem stained for myelin it can be seen how the gross structure of the medulla continues the organization of the spinal cord but becomes increasingly more complex in the rostral direction outer regions are usually white matter inner regions are usually gray matter with exceptions like the dorsal column nuclei In the most caudal medulla the bers of the corticospinal tract cross in the pyramidal decussation The pons contains mainly the pontine nuclei and the cerebellar peduncles that relay information to and from the cerebellum Fibers of the corticospinal tract descend through the pons en route to the pyramids The midbrain contains the superior colliculus on the dorsal surface and the cerebral peduncle on the ventral surface The cerebral aqueduct connects the third and fourth ventricles Throughout the brainstem there is a rough division between dorsal sensory and ventral motor structures Between these lies a compleX of over 100 loosely distributed nuclei called the reticular formation L web or net or tegmentum The nuclei of the reticular formation regulate sleepwake states and vegetative functions E Fourth ventricle Sulcus limitans Reticular formation Medial lemniscus Interior olivary nucleus V Cere hellum Pyramid Dorsal column nuclei Central canal FOurth ventricle Reticular formaticin Reticular formation Medial lemniscus Somatic sensory decussation and P nine in 39 medial lemniscus D t 0 uclei Corticospinal system Pyramid Dorsal column nuclei of central canal Approxmiate location xx E Pyramidal d ecu ssati on D A Motor nuclei B 39 Pyramid E Superior colliculus Figure 3 6 Myelinstained sections Tectum Feriaqueductal gray matter Cerebral aqueduct through three levels of the medulla From rostral to caudal inferior olivary nucleus A dorsal column nuclei B and pyramidal decussation C Levels of sections are indicated in the inset 7 7 and in Figure 35 Key medullar y Tegmentum structures are highlighted Reticular formatior Medial leinniscus Red nucleus figure 37 Myelinstained section through ports The level of section is indicated in the inset and in Figure 3 75 The reticular formation medial lernniscus and corticospinal system are outlined on the left side of the section Cerebral peduncle Substantial nigra 39Cort icospinal system Figure 38 Myelinstained section through the rostral midbrain at the level of the superior colliculus The level of section is indicated in the inset and in Fig ure 3 5 The reticular formation medial lemniscus and corticospinal system are outlined on the left side Functional Neuroanatomy NROSCI 1011 Gross Structure Higher Brain Centers Lateral ventricle Caudate nucleus Thalamus Putamen Globus palliclus internal capsule Third Hypothalamus ventricle Subthalarnicquot nucleus Hypro thalamic sulcus General Features of the Diencephalon The diencephalon shows a gradual transition from the brainstem without a clear junction It is a paired structurezthat is partly separated at the midline by the 3rd ventricle It is separated from the telencephalon by the lateral ventricles and the white matter of the internal capsule The diencephalon consists of a dorsal thalamus that processes sensory information and relays it to the cerebral cortex and a ventral hypothalamus that is a major visceral motor center the quothead ganglionquot of the autonomic nervous system The thalamus has two hemispheres joined by the gray matter interthalamic adhesion massa intermedia There are 6 major cell groups named for their positions around the white matter the E internal medullary lamina lateral anterior medial midline intralaminar and reticular Most relay information to the cortex the reticular connects only locally within the thalamus The reticular nucleus projects only within the thalamus and not to the cortex Tdel lm contains several small nuclei and is attached to the pituitary gland along its ventral surface Most hypothalamic function is directed toward regulation of the autonomic E nervous system and hormone release from the pituitary Figure 310 internal capsule The descending cortical axons collect into a discrete tract in the brain stem Adapted from Carpenter MB and Sutin J 1983 Human Neuro anatomy Baltimore Threedimensional sagittal View of the Williams amp Wilkins Descending llateral corticospinal pathway Primary motor cortex Cerebral cortex internal capsule posterior limbl lMidbrain Cerebral peduncle Ports Medulla Pyramid Pyramidal dlecussation Medullae spinal cord juncture Lateral Wei corticospinal tract Lateral column Cervical spinal cord Lateral motor nuclei ofthe ventral borrr Cerebral peduncle Pyramid Figure 188 Fibers that originate in the primary motor cortex and termi nate in the ventral horn of tlhe spinal cord constitute a significant part of the corticospinal tract The same axons are at various points in their projection part oi the internal capsule the cerebral peduncle the medullamr pyramid and the lateral corticospinal tract General Features of the Basal Ganglia The gray matter of the basal ganglia lies inferior and medial to the cortex and lateral to the diencephalon The basal ganglia are separated from the diencephalon by the internal capsule V which also partially divides the caudate nucleus from the putamen and globus pallidus The basal ganglia are separated from the cortex by the lateral ventricles and the external capsule Motor learning The basal ganglia are telencephalic structures participating inmotor planning They consist of the g caudate nucleus putamen and globus pallidus which are known together as the corpus V striatum striped body The caudate nucleus has the characteristic backwards Cshape of the telencephalon It is a continuous structure positioned just lateral to the lateral ventricle It is roughly divided into a head body and tail The tail ends just before the amygdala a limbic structure emotional Thalamus I 1 El 7 Caudate nucleus Horizontal plane of section Pulamen Tail of caudate Amygdaloid body Anterior Anterior horn of l 7 l lateral ventricle nsu a 7 Extreme capsule 7 Head of caudate Claustrum External capsule Anterior limb Putamen Internal Gen capsule Globus pallidus I J Posterior limb 1K 39 Q Third ventricle Thalamus Tail Of caudate Lateral ventricle Occipital lobe Posterior General Features of the Cerebral Cortex The major divisions lobes of the cortex are named for the overlying bones of the skull frontal parietal occipital and temporal Benee ef the Skull Side ltulive39g39r Skull Bones Top view The bony skull plates fuse during development at ridges called sutures suture The coronal suture crown fuses the frontal and parietal L wall of a cavity bones The suture between the two frontal bones disappears during development Central Postcentral sulcus gyms Precentral gyrus The sagittal suture fuses the two parietal bones at the midline PARIETAL LOBE FRONTAL LOBE The lamboid suture Gr lambda forms gg P39TAL between the parietal and occipital bones L occiput back of the head The squamous suture on the side of the skull separates the temporal L time or stretching bone from the parietal and occipital bones Lateral cerebral Cerebellum fissure TEMPORAL LOBE Superior temporal gyms The cortex is mittenshaped with the temporal lobe as the thumb This re ects the backwards C development of the telencephalon The cortex folds in on itself during development in order to increase surface area and the number of neurons that can t within the xed volume of the skull The folds are either shallow sulci s sulcus or deeper ssures The intervening rounded regions are gyri s gyrus The most prominent ssures are the longitudinal fissure which divides the cerebrum into two hemispheres and the lateral fissure Sylvian ssure which separates the temporal lobe from the overl ing cortices The lateral ssure is very deep and the cortex buried in its depths is the insula I The central sulcus separates the frontal and parietal lobes More speci cally it separates the primary somatosensory cortex in the postcentral gyrus from the primary motor cortex in the precentral gyrus Other major cortical regions are the primary Visual cortex in the occipital lobe and the primary auditory cortex in the temporal lobe E The occipital lobe is not segregated by any obvious sulcus on the outer surface Other smaller sulci and gyri are less constant and vary between individuals The primary sensory cortices receive their principal input from speci c relay nuclei in the thalamus Other cortical regions do not have their primary connections with the thalamus but with other 395 cortical areas These association cortices process higher order sensory motor and cognitive functionsJAxons connecting the cortices in the two hemispheres cross in the corpus callosum Corticospinal fibers White matter bundle The cortex is a laminated structure with layers of gray matter located external to white matter General Features of the Cerebellum The cerebellum or little brain is involved in coordinating movements error correction and motor learning It develops from the rhombic lip of the alar plate of the metencephalon pons This seems an exception to the general rule that alar plate structures have sensory functions But the cerebellum processes considerable sensory information in order to coordinate movement The cerebellum can be divided into a midline vermis and two lateral cerebellar hemispheres The Gray matter of E cerebellum is extensively folded forming transverse folia like gyri Deep fissures run mediolateral and divide the cerebellum into anterior posterior and flocculonodular lobes The cerebellum is connected to the brainstem by the cerebellar peduncles but is otherwise separated from it by the 4th ventricle Like the cerebral cortex the cerebellum is layered with gray matter external to white matter E However the cerebellum has additional gray matter structures the deep cerebellar nuclei internal to the white matter A 3 months B 4 months C 5 months Vermis Hemisphere Posterior Anterior and Figure 210 The cerebellum develops from the dorsal Posterior portion of the metencephalon a region termed the IObes rhombic lip Caudal views left and lateral views right are shown at three stages of development Adapted from Keibel F and Mall F P eds 1910 Flocculonodular 39 h 1912 Manual of Human Embryology 2 vols IObe Philadelphia Lippincott Flocculonodular lobe


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