thalamus nuclei
In order to lay the groundwork for understanding the functional organization of the sensory and motor pathways in Section B , it is necessary to have a familiarity with the nuclei of the thalamus, their organization, and names. There are two ways of dividing up the nuclei of the thalamus, namely, topographically and functionally. A. Topographically, the thalamus is subdivided by bands of white matter into a number of component parts. The main white matter band that runs within the thalamus is...
figure 67 midmedulla photographic view
This is a photographic image, enlarged, at the middle level of the medulla, with the cerebellum attached. This specimen shows the principal identifying features of the medulla, the pyramids ventrally on either side of the mid-line and the more laterally placed inferior olivary nucleus, with its scalloped borders. Between the olivary nuclei, on either side of the mid-line, are two dense structures, the medial lemniscus. The other dense tract that is recognizable in this specimen is the inferior...
noncortical structures
The term limbic system is the concept now used to include those parts of the brain that are associated with the functional definition of the limbic system. This is an overall diagram focusing on the noncortical components of the limbic system, both core and extended. These structures are found in the forebrain, the dienceph-alon, and also in the midbrain. Each of the structures, including the connections, will be discussed in greater detail in subsequent illustrations when this diagram,...
visual pathway 1
The visual image exists in the outside world, and is designated the visual field there is a visual field for each eye. This image is projected onto the retina, where it is now termed the retinal field. Because of the lens of the eye, the visual information from the upper visual field is seen in the lower retina and likewise for the lower visual field . The visual fields are also divided into temporal lateral and nasal medial portions. The temporal visual field of one eye is projected onto the...
mr angiogram mra
Recent advances in technology have allowed for a visualization of the major blood vessels supplying the brain, notably the arterial circle of Willis. This investigation does not require an invasive procedure described with the next illustration , although an injection intravenously of a contrast substance called gadolinium maybe used discussed with Figure 28B . Although the quality of such images cannot match the detail seen after an angiogram of select blood vessels shown in the next...
cranial nerve nuclei motor
The cranial nerves are peripheral nerves that supply the head region, except for the olfactory CN I and optic CN II nerves. Each cranial nerve is unique and may have one or more functional components, either sensory, motor, or both, and some also have an autonomic parasympathetic component. There are two kinds of motor functions 1. The motor supply to the muscles derived from somites, including CN III, IV, VI, and XII, and to the muscles derived from the branchial arches, called branchiomotor,...
figure 67a upper medulla crosssection
This section has the characteristic features of the medullary region, namely the pyramids anteriorly with the inferior olivary nucleus situated just laterally and behind. The cortico-spinal voluntary motor fibers from areas 4 and 6 go through the white matter of the hemispheres, funnel via the internal capsule posterior limb , continue through the cerebral peduncles of the midbrain and the pontine region, and emerge as a distinct bundle in the medulla within the pyramids. The cortico-spinal...
figure 67c lower medulla crosssection
The medulla seems significantly smaller in size at this level, approaching the size of the spinal cord below. The section is still easily recognized as medullary because of the presence of the pyramids anteriorly the cortico-spinal tract and the adjacent inferior olivary nucleus. The tegmentum contains the cranial nerve nuclei, the reticular formation and the other tracts. The nuclei of CN X and CN XII, as well as the descending nucleus and tract of V, are present as before as in the...
midpons crosssection
This section is taken through the level of the attachment of the trigeminal nerve. Anteriorly, the pontine nuclei and the bundles of cortico-spinal fibers are easily recognized. The pontine cells nuclei and their axons, which cross and then become the middle cerebellar peduncle, are particularly numerous at this level see Figure 55 . The cor-tico-spinal fibers are seen as distinct bundles that are widely dispersed among the pontine nuclei at this level see Figure 45 and Figure 48 . The...
medial forebrain bundle
Knowledge of this bundle of fibers is necessary if one is to understand the circuitry of the limbic system and how the limbic system influences the activity of the nervous system. The medial forebrain bundle MFB connects the sep-tal region with the hypothalamus and extends into the limbic midbrain it is a two-way pathway. Part of its course is through the lateral part of the hypothalamus where the fibers become somewhat dispersed as illustrated . There are further connections to nuclei in the...
figure 65b lower midbrain crosssection
This cross-section includes the cerebral peduncles, still located anteriorly and the substantia nigra located immediately behind these fibers. The unique feature in the lower midbrain is the decussation crossing of the superior cer-ebellar peduncles, which occupies the central area of the section this identifies the section as the inferior collicular level. Posteriorly the aqueduct is surrounded by the peri-aqueductal gray, and behind the aqueduct is the inferior colliculus. Often, the...
amygdala location and function
This diagram, which is the same as Figure 71, highlights a functional portion of the limbic system the amygdala and its pathways, the stria terminalis and the ventral amygdalofugal pathway. The septal region and functionally connected portions of the midbrain and medulla are also marked. The amygdala amygdaloid nucleus is a subcortical nuclear structure located in the temporal lobe in humans see Figure 25 and Figure 29 . As a subcortical nucleus of the forebrain, it belongs by definition with...
cerebellar efferents
This is again a dorsal view of the diencephalon, brainstem, and cerebellum, with the deep cerebellar intracerebellar nuclei. The cerebellar tissue has been removed in the midline, revealing the fourth ventricle as in Figure 10 the three cerebellar peduncles are also visualized from this posterior perspective see Figure 10 . The output from the cerebellum will be described, following the functional divisions of the cerebellum Vestibulocerebellum Efferents from the fasti-gial nuclei go to...
discriminative touch joint position vibration
This pathway carries the modalities discriminative touch, joint position, and the somewhat artificial sense of vibration from the body. Receptors for these modalities are generally specialized endings in the skin and joint capsule. The axons enter the spinal cord and turn upward, with no synapse see Figure 32 . Those fibers entering below spinal cord level T6 sixth thoracic spinal segmental level form the fasciculus gracilis, the gracile tract those entering above T6, particularly those from...
basal ganglia orientation
There are large collections of gray matter within the hemispheres, belonging to the forebrain, in addition to the white matter and the ventricles already described. These neuronal groups are collectively called the basal ganglia. Oftentimes the term striatum is used for the basal ganglia, but this term is not always used with neuroanatomical precision. Our understanding of the functional role of the basal ganglia is derived largely from disease states affecting these neurons. In general, humans...
lower illustration photographic view
This is a higher magnification of the medial aspect of the brain shown in Figure 17 . The interthalamic adhesion, fibers joining the thalamus of each side across the midline, has been cut see Figure 6, not labeled . The optic chiasm is seen anteriorly posteriorly, the tip of the pulv-inar can be seen. The midbrain includes areas where fibers of the visual system synapse. Fibers emerge from the pulvinar, the visually related association nucleus of the thalamus see Figure 12 and Figure 63 and...
figure 66c lower pons crosssection
This section is very complex because of the number of nuclei related to the cranial nerves located in the tegmental portion, including CN V, VI, VII, and VIII. Some of the tracts are shifting in position or forming. Anteriorly, the pontine nuclei have all but disappeared, and the fibers of the cortico-spinal tract are regrouping into a more compact bundle, which will become the pyramids in the medulla below . CN V The fibers of the trigeminal nerve carrying pain and temperature, that entered at...
vestibular nuclei and eye movements
The vestibular system carries information about our position in relation to gravity and changes in that position. The sensory system is located in the inner ear and consists of three semicircular canals and other sensory organs in a bony and membranous labyrinth. There is a peripheral ganglion the spiral ganglion , and the central processes of these cells, CN VIII, enter the brainstem at the cere-bellar-pontine angle, just above the cerebellar flocculus see Figure 6, Figure 7, and Figure 8B ....
limbic system synthesis
After studying the structures and connections of the limbic system in some detail a synthesis of the anatomical information with the notion of an emotional part of the brain seems appropriate. It is not easy to understand how the limbic system is responsible for the reactions required by the definition of emotion proposed in the Introduction to this section. The key structures of the limbic system are the limbic lobe the cortical regions, including the hippocam-pal formation and the...
extended limbic lobe
Other areas of the brain are now known to be involved in limbic functions and are included in the functional aspects of the limbic system. This includes large parts of the prefrontal cortex, particularly cortical areas lying above the orbit, the orbitofrontal cortex not labeled , as well as the cortex on the medial aspect of the frontal lobe to be discussed with Figure 77B . F Frontal lobe P Parietal lobe T Temporal lobe O Occipital lobe FIGURE 70B Limbic Lobe 2 Cingulum Bundle photograph
internal capsule photographic view with overlay
One of the most important sets of branches of the middle cerebral artery is found within the lateral fissure this artery has been dissected in Figure 58 . These are known as the striate arteries, also called lenticulostriate arteries see Figure 59B . These branches supply most of the internal structures of the hemispheres, including the internal capsule and the basal ganglia discussed with Figure 26 see also Figure 27 and Figure 29 . In this illustration, a coronal section of the brain see...
cerebral hemispheres medial photographic view
This view of the brain sectioned in the midline mid-sagittal plane is probably the most important view for understanding the gross anatomy of the hemispheres, the diencephalon, the brainstem, and the ventricles. The section has divided the corpus callosum, gone in between the thalamus of each hemisphere through the third ventricle , and passed through all parts of the brainstem. The medial aspects of the lobes of the brain are now in view. The central fissure does extend onto this part of the...
discriminative touch pain temperature
The sensory fibers include the modalities discriminative touch as well as pain and temperature. The sensory input comes from the face, particularly from the lips, all the mucous membranes inside the mouth, the conjunctiva of the eye, and the teeth. The fiber sizes and degree of myeli-nation are similar to the sensory inputs below the neck. The cell bodies of these fibers are found in the trigeminal ganglion inside the skull. The fibers enter the brainstem along the middle cere-bellar peduncle...
phineas gage
Phineas Gage has become a legendary figure in the annals of the history of the brain. In brief, Gage was working on the construction of a railway in the 1800s, when an untimely explosion drove a steel peg through his brain. The steel peg is said to have penetrated the orbit and the frontal lobes, much like the surgical procedure described above, emerging through the skull. He survived and lived on his personality changes, which have been well documented, subsequent to this accident concur with...
spinal cord crosssectional views upper diagram
The upper diagram is a cross-section through the spinal cord at the C8 level, the eighth cervical segmental level of the spinal cord not the vertebral level, see Figure 1 . The gray matter is said to be arranged in the shape of a butterfly or somewhat like the letter H . The gray matter of the spinal cord contains a variety of cell groups i.e. nuclei , which subserve different functions. Although it is rather difficult to visualize, these groups are continuous longitudinally throughout the...
spinal cord cauda equina photograph
This is a higher magnification photographic image of the lowermost region of the spinal cord, the sacral region. The tapered end of the spinal cord is called the conus med-ullaris, and this lower portion of the cord corresponds approximately to the sacral segments. The collection of dorsal and ventral nerve roots, below the level of the termination of the cord, is collectively called the cauda equina. These roots, which belong to the lumbar and sacral segments of the spinal cord, fill the...
cortical structures
The limbic lobe refers to cortical areas of the limbic system. These cortical areas, which were given the name limbic, form a border limbus around the inner structures of the diencephalon and midbrain see Figure 17 and Figure 70B . The core cortical areas include the hippoc-ampal formation, the parahippocampal gyrus, and the cin-gulate gyrus. There are a number of cortical areas located in the most medial also called mesial aspects of the temporal lobe in humans that form part of this limbus....
figure 66a upper pons crosssection
This level is presented mainly to allow an understanding of the transition of midbrain to pons. This particular section is taken at the uppermost pontine level, where the trochlear nerve, CN IV, exits below the inferior collicu-lus, see Figure 7 . This is the only cranial nerve that exits posteriorly its fibers cross decussate before exiting see Figure 48 . Anteriorly, the pontine nuclei are beginning to be found. Cortico-pontine fibers will be terminating in the pontine nuclei. From these...
septal region and limbic midbrain
This illustration provides detailed information about other important parts of the limbic system, the septal region and the limbic midbrain. The pathway that interconnects the hypothalamus and these areas is the medial forebrain bundle. The septal region includes both cortical and subcortical areas that belong to the forebrain. The cortical areas, named the septal cortex, are found under the rostrum of the corpus callosum the thin inferior portion of the corpus callosum, see Figure 17 and...
limbic structures and the lateral ventricle
The temporal lobe is a more recent addition in the evolution of the hemispheres and develops later in the formation of the brain. During the development of the temporal lobe, a number of structures migrate into it the lateral ventricle, the hippocampal formation, the caudate nucleus, as well as various tracts, the fornix and stria terminalis. The lateral ventricle and associated structures form a crescent in the shape of a reverse letter C see Figure OL and Figure 20A . These relationships are...
basal ganglia circuitry
This is the same view of the basal ganglia as shown previously see Figure 24 , with the head of the caudate nucleus removed. The illustration includes the two other parts of the basal ganglia as a functional system the subthalamic nucleus and the substantia nigra. The subthalamic nucleus S is situated in a small region below the level of the thalamus. The substantia nigra SN is a flattened nucleus located in the midbrain region. It is composed of two parts see Figure 65A . The pars compacta has...
sensory nuclei and ascending tracts
This diagrammatic presentation of the internal structures of the brainstem is shown from the dorsal perspective as in Figure 10 and Figure 36 . The information concerning the various structures will be presented in an abbreviated manner, as most of the major points have been reviewed previously. The orientation of the cervical spinal cord representation should be noted. Dorsal column-medial lemniscus discriminative touch, joint position, and vibration and its nuclei Anterolateral system pain...
reticular formation nuclei
In this diagram, the reticular formation is being viewed from the dorsal posterior perspective see Figure 10 and Figure 40 . Various nuclei of the reticular formation, RF, which have a significant known functional role, are depicted, as well as the descending tracts emanating from some of these nuclei. Functionally, there are afferent and efferent nuclei in the reticular formation and groups of neurons that are distinct because of the catecholamine neurotransmitter used, either serotonin or...
auditory gyri photographic view
This photographic view of the left hemisphere is shown from the lateral perspective see Figure 14A . The lateral fissure has been opened, and this exposes two gyri, which are oriented transversely. These gyri are the areas of the cortex that receive the incoming auditory sensory information first. They are named the transverse gyri of Heschl as was also shown in the previous illustration , the auditory gyri, areas 41 and 42 see Figure 60 . The lateral fissure forms a complete separation between...
reticular formation organization
The reticular formation, RF, is the name for a group of neurons found throughout the brainstem. Using the ventral view of the brainstem, the reticular formation occupies the central portion or core area of the brainstem from midbrain to medulla see also brainstem cross-sections in Figure 65-Figure 67 . This collection of neurons is a phylogenetically old set of neurons that functions like a network or reticulum, from which it derives its name. The RF receives afferents from most of the sensory...
List Of Illustrations
FIGURE OA Overview Diagram Anterior View FIGURE OL Overview Diagrsm Lateral View FIGURE 1 Spinal Cord 1 Longitudinal Vertebral View FIGURE 2A Spinal Cord 2 Longitudinal View photograph FIGURE 2B Spinal Cord 3 Cervical Region photograph FIGURE 2C Spinal Cord 4 Cauda Equina photograph FIGURE 3 Spinal Cord 5 MRI Longitudinal View radiograph FIGURE 4 Spinal Cord 6 Cross-Sectional Views FIGURE 5 Spinal Cord 7 MRI Axial View radiograph FIGURE 6 Brainstem 1 Ventral View with Cranial Nerves FIGURE 7...
white matter lateral dissected view association bundles photograph
The dorsolateral aspect of the brain is being viewed in this photograph see Figure 14A . The lateral fissure has been opened, with the temporal lobe below deep within the lateral fissure is the insula see Figure 14B and Figure 39 . Under the cerebral cortex is the white matter of the brain. It is possible to dissect various fiber bundles not easily using a blunt instrument e.g., a wooden tongue depressor . Some of these, functionally, are the association bundles, fibers that interconnect...
brainstem and cerebellum dorsal inferior photographic view
This is a photograph of the same specimen as Figure 9A, but the specimen is tilted to reveal the inferior aspect of the cerebellum and the posterior aspect of the medulla. The posterior aspect of the pons is still covered by the cerebellum see Figure 10 . The posterior aspect of the midbrain can no longer be seen. The upper end of the thalamus is still in view. The horizontal fissure of the cerebellum is now clearly seen it is used as an approximate divider between the superior and inferior...
cerebral cortex dorsolateral photographic view
This is a photographic image of the same brain as shown in the previous illustration, tilted slightly, to show the dorsolateral aspect of the hemispheres. The edge of the other hemisphere with meninges is still in view. It is now possible to identify the sulci and fissures with more certainty. The central fissure often called the fissure of Rolando is seen more completely, dividing the frontal lobe anteriorly from the parietal lobe posteriorly. The deep lateral fissure is clearly visible see...
sagittal view schematic
This is a schematic drawing of the brainstem seen in a midsagittal view see Figure 17 and Figure 18 . This view is being presented because it is one that is commonly used to portray the brainstem. The learner should try to correlate this view with the ventral view shown in the previous diagram. This schematic also will be shown in each of the cross-section diagrams, with the exact level indicated, in order to orient the learner to the plane of section through the brainstem. The location of some...
special tract
The dorsolateral fasciculus, better known as the tract of Lissauer see Figure 32 , carries intersegmental information, particularly relating to pain afferents. The functional aspects of each of these tracts should be reviewed at this time by noting the loss of function that would be found following a lesion of the various pathways. An acute injury to the cord, such as severing of the cord following an accident, will usually result in a complete shutdown of all spinal cord functions, called...
blood supply
The anterior spinal artery, the main blood supply to the spinal cord, comes from branches from each of the vertebral arteries that join see Figure 58 it descends in the midline see Figure 2B and supplies the ventral horn and the anterior and lateral group of tracts, including the lateral cortico-spinal pathway. The posterior spinal arteries supply the dorsal horn and the dorsal columns. The blood supply to the spinal cord was reviewed with Figure 2B it is known that this blood supply is...
connections and function
In the temporal lobe, the six-layered parahippocampal gyrus provides extensive input to the adjacent hippocam-pal formation. The hippocampal formation also receives input from the amygdala. There are extensive interconnections within the component parts of the hippocampal formation itself. Part of the output of the hippocampal formation is directed back to the parahippocampal gyrus, establishing a strong reciprocal connection. This is analogous to the cortical association pathways described...
histological staining
A variety of histological stains are available that can feature different normal and abnormal components of tissue. For the nervous system, there are many older stains and an ever-increasing number of newer stains using specific antibody markers, often tagged with fluorescent dyes. In general, the stains include those for Cellular components, the cell bodies of neurons and glia and cells lining blood vessels these are general stains such as Hematoxylin amp Eosin H amp E . The neurons,...
photographic view with midbrain
This is another brain specimen showing the inferior surface of the brain, in which the brainstem has been sectioned through at the level of the midbrain, removing most of the brainstem and the attached cerebellum. The cut surface of the midbrain is exposed, showing a linear area of brain tissue, which is black in coloration this elongated cluster of cells is the nucleus of the midbrain called the substantia nigra, and consists of neurons with pigment inside the cells discussed with Figure 65 ....
pain temperature crude touch
This pathway carries the modalities of pain and temperature and a form of touch sensation called crude or light touch. The sensations of itch and tickle, and other forms of sensation e.g., sexual are likely carried in this system. In the periphery the receptors are usually simply free nerve endings, without any specialization. These incoming fibers sometimes called the first order neuron enter the spinal cord and synapse in the dorsal horn see Figure 4 and Figure 32 . There are many collaterals...
functional lobes
The cerebellum has been subdivided anatomically according to some constant features and fissures see Figure 9A and Figure 9B . In the midline, the worm-like portion is the vermis the lateral portions are the cerebellar hemispheres. The horizontal fissure lies approximately at the division between the superior and the inferior surfaces. The deep primary fissure is found on the superior surface and the area in front of it is the anterior lobe of the cerebellum. The only other parts to be noted...
mlf and associated tracts
This diagram shows the brainstem from the posterior perspective as in Figure 10 and Figure 40 . Note the orientation of the spinal cord with the ventral horn away from the viewer . The MLF is a tract within the brainstem and upper spinal cord that links the visual world and vestibular events with the movements of the eyes and the neck, as well as linking up the nuclei that are responsible for eye movements. The tract runs from the midbrain level to the upper thoracic level of the spinal cord....
figure 66 upper pons photographic view
This is a photographic image, enlarged, of the pontine region, with the cerebellum attached. The section is done at the level of the upper pons, as indicated in the upper images of the ventral view of the brainstem and in the midsagittal view. The unique nucleus present at this level is the locus ceruleus, a small nucleus whose cells have pigment, much like those of the substantia nigra, pars compacta see Figure 65 . As with that nucleus, the pigment is lost during histological processing. The...
brainstem and cerebellum dorsal photographic view
This specimen of the brainstem and diencephalon, with the cerebellum attached, is being viewed from the dorsal or posterior perspective. The third ventricle, the ventricle of the diencephalon, separates the thalamus of one side from that of the other see Figure OA and Figure 20A also Figure 17 and Figure 21, where the brain is separated down the midline in the midsagittal plane . The dienceph-alon is to be discussed with Figure 11. Additional structures of the brainstem are seen from this...