Chapter 1: summary of the Nervous mechanism

Nachum Dafny, Ph.D., room of Neurobiology and Anatomy, The UT clinical School at Houston Reviewed and also revised 07 Oct 2020

The human being nervous mechanism is split into the central nervous device (CNS) and the peripheral nervous mechanism (PNS). The CNS, in turn, is divided into the mind and the spinal cord, i m sorry lie in the cranial cavity that the skull and the vertebral canal, respectively. The CNS and also the PNS, acting in concert, integrate sensory information and control motor and also cognitive functions.

You are watching: The thick band of neurons that connects the right and left cerebral hemispheres is called the

1.1 The central Nervous device (CNS)

Figure 1.1 Lateral watch of human being embryo in ~ the start of the third (A) and fifth (B) mainly of gestation.

The adult human mind weighs between 1,200 come 1,500 g and contains about one sunshine cells. It rectal a volume of about 1400 cc - around 2% that the full body weight, and also receives 20% that the blood, oxygen, and also calories provided to the body. The adult spinal cord is about 40 come 50 centimeter long and occupies about 150 cc. The mind and the spinal cord happen in early development from the neural tube, which increases in the prior of the embryo to type the 3 primary mind divisions: the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain) (Figure 1.1A). These three vesicles further identify into five subdivisions: telencephalon, diencephalon, mesencephalon, metencephalon, and the myelencephalon (Figure 1.1B). The mesencephalon, metencephalon, and also the myelencephalon comprise the brain stem.

The telencephalon consists of the cerebral cortex (cortex is the external layer that the brain), which represents the highest possible level that neuronal company and function (Figures 1.2A and also 1.2B). The cerebral cortex is composed of various varieties of cortices (such together the olfactory bulbs, number 1.2B) as well as closely connected subcortical frameworks such together the caudate nucleus, putamen, globus, amygdala and the hippocampal development (Figure 1.2C).

Figure 1.2 Lateral (A) and also ventral (B) see of the cerebral cortex. Coronal watch (C) of subcortical structures.

The diencephalon consists of a complicated collection that nuclei lie symmetrically on either side of the midline. The diencephalon has the thalamus, hypothalamus, epithalamus and subthalamus (Figure 1.3).

Figure 1.3 The main diencephalon nuclei.

The mesencephalon (or midbrain) consists of number of structures roughly the cerebral aqueduct such together the periaqueductal gray (or central gray), the mesencephalic reticular formation, the substantia nigra, the red cell core (Figure 1.4), the superior and inferior colliculi, the cerebral peduncles, some cranial nerve nuclei, and the forecast of sensory and motor pathways.

Figure 1.4 Subcortical diencephalic and also mesencephalic structures.

Figure 1.5 Lateral view of the metencephalon and a spinal cord ar with ventral and also dorsal root fibers, and also dorsal root ganglia.

The metencephalon includes the pons and also the cerebellum. The myelencephalon (spinal cord-like) has the open and closed medulla, sensory and also motor nuclei, forecast of sensory and also motor pathways, and also some cranial nerve nuclei.

The caudal finish of the myelencephalon establishes into the spinal cord. The spinal cord is an elongated cylindrical framework lying in ~ the vertebral canal, which has the central canal and the surrounding gray matter. The gray issue is written of neurons and also their supporting cells and also is enclosed by the white matter that is written of a thick layer that ascending and descending nerve fibers. The spinal cord is an important link between the peripheral concerned system and the brain; the conveys sensory information originating from various external and internal sites via 31 bag of spinal nerves (Figure 1.5). This nerves make synaptic relations in the spinal cord or in the medulla oblongata and also ascend come subcortical nuclei.

Figure 1.6 The main nervous system, which consists of the spinal cord and also the brain, is the most defended organ in the person body. It is protected from the external environment by three barriers: skull, meninges, and cerebral spinal fluid (CSF).

The meninges room composed by three fibrous connective tissues (Figure 1.6). The most outside is a thick collagenous connective organization envelope well-known as the dura mater (Latin because that “hard mother”). The second, or the intermediated membrane, is a vulnerable non-vascular membrane of well collagenous layer of reticular fibers developing a web-like membrane, recognized as the arachnoid (Greek because that “spider”). It is separated native the inside pia class by subarachnoid space, i m sorry is filled v cerebrospinal fluid. The inside most fragile connective tissue membrane the collagenous is the pia mater, a slim translucent elastic membrane adherent to the surface ar of the mind and the spinal cord. Blood vessels located on the surface ar of the brain and the spinal cord are uncovered on height of the pia matter. The meninges are subject to viral and also bacterial infection well-known as meningitis, a life-threatening condition that requires instant medical treatment.

The room between the skull and also the dura is recognized as the epidural space. The an are between the dura and also the arachnoid is well-known as the subdural space. The space between the arachnoid and the pia is recognized as the subarachnoid space. In this space, over there is a clean liquid known as the CSF. The CSF serves to assistance the CNS, and also to cushion and protect that from physical shock and trauma. The CSF is produced by the choroid plexus, i m sorry is composed of a dedicated secretory ependymal layer located in the ventricular system.

The ventricular mechanism is a derivative that the primitive embryonic neural canal. This mechanism is an interconnected series of spaces in ~ the brain, which contains the CSF (Figure 1.7).

Figure 1.7 The ventricular system in four different angles.

In general, the CNS deserve to be separated into three key functional components: the sensory system, the engine system, and also homeostatic and also higher mind functions. The sensory system consists of the somatosensory, viscerosensory, auditory, vestibular, olfactory, gustatory, and visual systems. The motor system consists of motor units, and the somatic (skeletal muscle) system, the spinal reflexes, the visceral (autonomic) system, the cerebellum, number of subcortical and cortical sites, and the brain stem ocular motor regulate system. The homeostatic and greater functional system has the hypothalamus, cortical locations involved in motivation, insight, personality, language, memory, imagination, creativity, thinking, judgment, psychological processing, and also subcortical locations involved in learning, thought, consciousness, memory, attention, emotionally state, sleep and also arousal cycles.

1.2 The Cerebral Hemispheres

The largest and also most apparent parts of the human brain are the cerebral hemispheres. The cerebrum has an external layer - the cortex, i beg your pardon is created of neurons and their sustaining cells, and in living brain, has a gray color thus referred to as the gray matter. Under the gray matter is the white matter, i beg your pardon is created of myelinated ascending and also descending nerve fibers, and also in living mind have a white color. Installed deep within the white matter are aggregates that neurons exhibiting gray color and also known together subcortical nuclei. The cerebral hemispheres are partially separate indigenous each other along the midline through the interhemispheric fissure (deep groove) the falx cerebri (Figure 1.8A); Posteriorly, there is a transverse fissure the separates the cerebral hemisphere native the cerebellum, and also contains the tentorium cerebellum. The hemispheres are linked by a big C-shaped fiber bundle, the body callosum, i beg your pardon carries information between the 2 hemispheres.

Figure 1.8 6 cortical lobes: Dorsal view (A), Lateral check out (B), Mid-sagittal section mirroring the limbic lobe (in green) (C), and Horizontal section showing the insular cortex (D).e

For descriptive purposes each cerebral hemisphere can be split into six lobes. Four of this lobes are called according come the overlying skeleton of the skull as follows: frontal, parietal, occipital and temporal (Figures 1.8A and also 1.8B), the fifth one is situated internally come the lateral sulcus – the insular lobes (Figure 1.8B and also 1.8D), and also the 6th lobe is the limbic lobe (Figure 1.8C) which includes the limbic device nuclei. No the insular lobe no one the limbic lobe is a true lobe. Although the limits of the miscellaneous lobes are rather arbitrary, the cortical areas in every lobe are histologically distinctive.

The surface ar of the cerebral cortex is highly convoluted v folds (gyri), separate from each various other by elongated grooves (sulci). These convolutions permit for the development of the cortical surface area without increasing the size of the brain. Top top the lateral surface ar of the cerebral hemisphere there space two significant deep grooves-sulci (or fissure), the lateral fissure (of Sylvian) and also the central sulci (of Rolando), this sulci carry out landmarks for topographical orientation (Figure 1.9A). The central sulcus separates the frontal lobe from the parietal lobe and also runs indigenous the premium margin that the hemisphere near its midpoint obliquely downward and also forward till it nearly meets the lateral fissure (Figures 1.8A and 1.8B). The lateral fissure, separating the frontal and also parietal lobes indigenous the temporal lobe, begins inferiorly in the basal surface of the brain and extends laterally posteriorly and also upward, separating the frontal and parietal lobes native the temporal lobe (Figure 1.9A). The frontal lobe is the part which is rostral come the central sulcus and over the lateral fissure, and it rectal the anterior one third of the hemispheres (Figures 1.8 and 1.9). The limits of the parietal lobe are not precise, other than for that rostral border – the main sulcus. The occipital lobe is the part which is caudal to the parietal lobe (Figures 1.8 and 1.9). Along the lateral surface of the hemisphere, one imaginary line connecting the tip of the parietal-occipital sulcus and also the preoccipital notch (Figure 1.9A), different the parietal lobe from the occipital lobe. On the medial surface ar of the hemisphere (Figure 1.9B), parieto-occipital sulcus forms the rostral boundary of the parietal lobe. The temporal lobe lies ventral to the lateral sulcus, and also on that lateral surface, it displays three diagonal line oriented convolutions-the superior, middle, and inferior temporal gyri (Figure 1.9A). The insula lies in the depth of the lateral sulcus. It has actually a triangle cortical area v gyri and sulci (Figures 1.8B and also 1.8D, and Figure 1.9A). The limbic lobe is composed of numerous cortical and subcortical locations (Figure 1.9B).



Figure 1.9 illustration of the various cortices, sulci and gyri (A) and mid-sagittal drawing emphasizes the limbic lobe (in green) (B).

The cerebral cortex is a functionally organized organ. A functionally organized system is a set of neurons connected together come convey a details type(s) of details to attain a details task. The is possible to identify on the cerebral cortex primary sensory areas, secondary sensory areas, main motor area, premotor area, supplementary engine area and association areas, i beg your pardon are committed to the integration of motor and sensory information, pundit activity, thinking and comprehension, execution of language, memory storage and recall.

The frontal lobe is the largest of the brain lobes and is made up of four gyri, precentral gyrus the parallels the main sulcus, and three horizontal gyri: the superior, middle, and inferior frontal gyri. The worse frontal gyrus is consisted of of three parts: the orbital, the triangular and also opercular. The hatchet opercular describes the “lips of the lateral fissure. Finally, the right gyrus (gyrus rectus) and also the orbit gyri kind the basic of the frontal lobe (Figure 1.9B). Four general functional locations are in the frontal lobe. They space the major motor cortex, wherein all parts of the body room represented, the premotor and supplementary motor areas. A region concerned with the engine mechanisms of decided formulation comprised of the opercular and also triangular parts of the inferior frontal gyrus are well-known as Broca’s speech area, and also the remainder that the prefrontal cortex is associated in psychological activity, personality insight, foresight, and reward. The orbital part of the prefrontal cortex is essential in the appropriate switching between mental sets and also the regulation the emotion.

The parietal lobe is consisted of of three gyri: postcentral gyrus, superior and inferior parietal gyri (Figure 1.9A). The postcentral gyrus is instantly behind the main sulcus which creates its anterior boundary. The postcentral gyrus comprises the main somatosensory cortex i m sorry is pertained to with somatosensory reception, integration and processing sensory information from the surface ar of the body and from the viscera, and also is necessary for the formulation the perception. Caudal to the postcentral gyrus is the worse parietal gyrus. The intraparietal sulcus off the posterior parietal gyrus from the worse parietal gyrus. The worse parietal gyrus represents the cortical association area which integrates and processes sensory info from many modalities such together auditory and visual information. The inferior parietal gyrus, i beg your pardon is well-known as Wernicke"s area, is likewise important for language and also reading skills, vice versa, the remarkable parietal gyrus is involved with body image and spatial orientations.

The temporal lobe is developed by three obliquely oriented gyri: the superior, middle, and inferior temporal gyri (Figure 1.9A). Inferomedial to the inferior temporal gyrus are the occipitotemporal and also the parahippocampal gyri, which room separated by the collateral sulcus. The upper surface ar of the exceptional temporal gyrus, i beg your pardon extends into the lateral fissure, is called the transverse temporal gyrus (of Heschl) and also is the major auditory cortex. The caudal part of the remarkable temporal gyrus, i m sorry extends as much as the parietal cortex, forms component of Wernicke’s area. Wernicke’s area is concerned, in part, with handling the listening information and also is vital in the understanding of language. The inferior part of the temporal lobe (i.e., the occipitotemporal gyri) is associated in visual and cognitive processing. Much more medially is the parahippocampal gyrus, which is associated in learning and also memory. Sections of the frontal, parietal, and also temporal lobes, which are adjacent to the lateral sulcus and also overlie the insular cortex, are known as the operculum. The inferomedial surface of the temporal lobe is comprised of the uncus and the parahippocampal gyrus medially. The inferior surface of the temporal lobe rests ~ above the tentorium cerebelli.

The occipital lobe is the most caudal part of the brain, lies ~ above the tentorium cerebelli (Figure 1.9A) and also is comprised of number of irregular lateral gyri. Top top its medial surface, there is a significant fissure – the calcarine fissure and also parieto-occipital sulcus. The calcarine fissure (sulcus) and also the parieto-occipital sulcus also define a cortical region known together the cuneus. The cuneus sulcus divides the occipital lobe into the cuneus dorsally and also ventrally into the lingual gyrus. The occipital lobe consists of the primary and also higher-order intuitive cortex.

The insula lobe is located deep within the lateral fissure and can be viewed only once the temporal and also the frontal lobes are separated (Figures 1.8B and 1.8D). The insula is defined by several lengthy gyri and also sulci, the gyri breves and also gyri longi. Over there is some evidence that the insular cortical areas are involved in nociception and also regulation the autonomic function.

The limbic lobe is no a true lobe and is consisted of of number of cortical areas such as the cingulate and parahippocampal gyri, part subcortical areas like the hippocampus, amygdala, septum, and other locations with their corresponding ascending and descending relations (Figures 1.8C and 1.9B). The limbic lobe is connected in memory and also learning, drive connected behavior, and also emotional function.

There are subcortical areas in the telencephalon favor the basal ganglia and also the amygdaloid cell nucleus complex. The body callosum is a repertoire of nerve fibers that affix the two hemispheres. The corpus callosum is separated into rostrum (head), body, the most rostrally component is the genu (knee) v connecting the rostrum and the body, and also the splenium at the caudal extremity (Figure 1.10). The body callosum plays vital role in transferring info from one hemisphere to the other.

1.3 The Diencephalon

The second significant derivative of the prosencephalon is the diencephalon. The diencephalon is the many rostral structure of the mind stem; that is installed in the inferior facet of the cerebrum. The posterior commissure is the junctional landmark in between the diencephalon and also the mesencephalon. Caudally, the diencephalon is constant with the tegmentum that the midbrain. During development the diencephalon differentiates into 4 regions: thalamus, hypothalamus, subthalamus and also epithalamus (Figure 1.11) The epithalamus comprises the stria medullaris habenular trigone, pineal gland and the posterior commissure

Figure 1.11 Mid-sagittal illustration showing the key structures of the diencephalon and also rhombencephalon.

1.4 The mind Stem

The mind stem consists of mesencephalon (midbrain), metencephalon, and also myelencephalon. The metencephalon and also myelencephalon together compose the rhombencephalon (hindbrain), i m sorry divides right into pons, and medulla oblongata (Figures 1.11 and also 1.12).

Mesencephalon (midbrain) is constant with the diencephalon rostrally and also with the pons caudally. The midbrain is the smallest part of the mind stem, being about 2 centimeter in length. It consists of a tectum posteriorly, a tegmentum inferiorly, and also a base anteriorly. The tectum forms the roof that the cerebral aqueduct, i m sorry connects the 3rd ventricle with the 4th ventricle and also the tegmentum the floor. The base of the midbrain consists of the cerebral peduncle, i m sorry contain nerve yarn descending native the cerebral cortex. The nuclei of the third (oculomotor), the fourth (trochlear) and component of the 5th (trigeminal) are located in the midbrain tegmentum. The red nucleus and also the substantia nigra, two influential nuclei, are additionally found in the midbrain tegmentum. The midbrain tectum is developed by 2 pairs the rounded structures: the superior and inferior colliculi. The superior and inferior colliculi (Figure 1.12) are connected in visual and also auditory features respectively.

Pons is consistent with the midbrain and is created of two parts, the pontine tegmentum (located internally) and also the basilar pons. At the level the the pons, the cerebral aqueduct has increased to form the 4th ventricle (Figure 1.12). The cerebellum is located posterior to the pons and forms component of the roof (tectum) of the forth ventricle. The pons has nuclei that receive axons from miscellaneous cortical areas. Projections from the axons of this pontine neurons form large transverse fiber bundles the traverse the pons and ascend come the contralateral cerebellum via the middle cerebellar peduncles. Also, in ~ the pons base and tegmentum room longitudinally ascending and also descending fibers. The nuclei of the fifth (trigeminal), 6th (abducens), 7th (facial) and also the 8th (vestibulocochlear) nerves are situated in the pons tegmentum.

Medulla Oblongata (myelencephalon is additionally known as the medulla). The medulla lies in between the pons rostrally and the spinal cord caudally. It is constant with the spinal cord just over to foramen magnum and also the an initial spinal nerve. The posterior surface ar of the medulla creates the caudal half of the fourth ventricle floor and the cerebellum, that is roof (Figure 1.12). The basic of the medulla is developed by the pyramidal-descending fibers from the cerebral cortex. The medulla tegmentum includes ascending and descending fibers and also nuclei native the 9th (glossopharyngeal), 10th (vagus), 11th (accessory) and the 12th (hypoglossal) nerves. The corticospinal yarn (pyramid) space alongside the anterior mean fissure, and decussate (cross the midline) to the contralateral next on their method to the spinal cord. Other prominent structures in the medulla space the worse olive, and the worse cerebellar peduncle. The medulla consists of nuclei which manage respiration, swallowing, sweating, gastric secretion, cardiac, and also vasomotor activity.

The arterial blood supply to the mind is acquired from two arterial systems: the carotid system and the vertebrobasilar system. A series of one anastomotic channels lying at the basic of the brain, known as the circle of Willis, patent communication between these two solution (Figure 1.13).

The arterial blood it is provided to the spinal cord is obtained from two branches the vertebral artery, the anterior and also two posterior spinal arteries which run the length of the spinal cord and form an irregular plexus around it (Figure 1.14).

The PNS consists of 31 bag of spinal nerves, 12 pairs of cranial nerves, the autonomic concerned system and the ganglia (groups that nerve cells outside the CNS) connected with them. Likewise included in the PNS are the sensory receptor organs. The receptor organs room scattered in all parts of the body, sense and also perceive alters from external and also internal organs, climate transform this information to electrical signals, i m sorry are carried via an extensive nervous network come the CNS (Figure 1.15). The cranial and spinal nerves contain nerve fibers the conduct details to-afferent-(Latin for lug toward) and also from-efferent (Latin for bring away) the CNS. Afferent fibers convey sensory information from sensory receptors in the skin, mucous membranes, and internal organs and from the eye, ear, nose and also mointer-base.net to the CNS; the efferent fibers convey signal from cortical and subcortical centers come the spinal cord and from there to the muscle or autonomic ganglia the innervate the visceral organs. The afferent (sensory) fibers enter the spinal cord via the dorsal (posterior) root, and also the efferent (motor) fibers departure the spinal cord via the ventral (anterior) root. The spinal nerve is formed by the joining of the dorsal and also the ventral roots. The cranial nerves leaving the skull and the spinal cord nerves leave the vertebrae v openings in the bone dubbed foramina (Latin for opening).

The PNS is separated into 2 systems: the visceral system and also the somatic system. The visceral system is also known as the autonomic system. The autonomic nervous device (ANS) is often thought about a different entity; return composed partly in the PNS and also partially in the CNS, that interfaces in between the PNS and the CNS. The primary role of the ANS is come regulate and also control unconsciousness attributes including visceral, smooth muscle, cardiac muscle, vessels, and glandular function (Figure 1.16). The ANS can be divided into 3 subdivisions:

The sympathetic (or the thoracolumbar) subdivision linked with neurons situated in the spinal gray between the thoracic and also the upper lumbar levels; The parasympathetic (or craniosacral) subdivision is connected with the 3rd, 7th, 9th and the 10th cranial nerves as well as with the 2nd, 3rd, and 4th sacral nerves; The enteric subdivision is a facility neuronal network in ~ the wall surfaces of the gastrointestinal system and contains an ext neurons than the spinal cord. The visceral (autonomic) system regulates the interior organs external the realm of mindful control. The PNS ingredient of the somatic system consists of the sensory receptors and also the neurons innervating them and also their nerve yarn entering the spinal cord. The visceral and also the somatic nervous mechanism are primarily came to with their own functions, but also work in harmony v other facets of the concerned system.

1.6 Orientation to the main Nervous System

This section illustrates representative sections with the CNS in order come acquaint the reader with influential structures and help in the recognition of the level and also orientation the the section. It additionally provides landmarks because that locating nuclei and also tracts connected in sensory and motor functions. Directional terms are provided in relenten the locations of frameworks in the CNS.

Figure 1.17 Orientation of the main nervous system of the spinal cord and also different brain sections.

Keep in mind that specific terms were emerged to define the nervous system of quadrupeds and may have a contempt different meaning when applied to bipeds. For example, the ventral surface of the quadruped spinal cord is equivalent to the anterior surface ar of the biped (Figure 1.18). In the complying with descriptions, the terms are applied to a standing human. The terms rostral and anterior describe a direction in the direction of the face/nose. The state caudal and posterior refer to a direction towards the buttocks/tail. The terms inferior and superior typically refer to spatial relationships in a upright direction (Figure 1.18). A coronal section is parallel to the vertical aircraft and a midcoronal section would division the head into anterior and also posterior halves (Figure 1.19). The sagittal section is likewise parallel to the upright plane, but a midsagittal ar would division the head right into right and also left halves. The horizontal (axial) ar is parallel to the horizontal aircraft and a mid-horizontal section would division the head into superior and also inferior halves. Transverse or overcome sections of the spinal cord of people are bring away in a aircraft perpendicular come the upright (i.e., in the horizontal aircraft of the head). Many electromagnetic imaging techniques create images that the mind in the coronal, horizontal (axial) and sagittal planes. The representative sections room transverse sections with the spinal cord and brain stem and also coronal sections v the telencephalon and diencephalon (Figure 1.17).

Transverse section through the Spinal Cord. Number 1.17A illustrates a ar taken in ~ the level that the thoracic spinal cord. The spinal cord neuron (gray matter) form a main core taking a butterfly configuration that is surrounding by nerve fibers (white matter). In the left and right halves that the spinal cord, the gray matter is organized into a dorsal horn and ventral horn through the intermediary gray located between them. In the thoracic spinal cord, i beg your pardon is illustrated in this figure, a lateral horn expand laterally from the intermediary gray (Figure 1.17A). The spinal cord white matter is subdivided into the posterior white column, the anterior white column and the lateral white column. The anterior white commissure joins the 2 halves that the spinal cord and is located ventral to the intermediary gray. The dorsal source fibers go into the spinal cord in ~ the dorsolateral sulcus and also the fibers of the ventral root fibers exit the spinal cord in many fine bundles with the ventral funiculus (see number 1.5).

Transverse section through the Medulla. Figure 1.17B is a section taken at the level the the upper medulla. Landmark structures include the 4th ventricle, hypoglossal nucleus, inferior cerebellar peduncle, inferior olivary complex and the pyramids. Together in the spinal cord section, the fiber tracts, the inferior cerebellar peduncle and pyramids, show up light in this ar whereas the nuclei in the worse olivary complex appear dark.

Transverse ar through the Pons. Number 1.17C is a section taken at the level that the mid pons. Landmark structures encompass the 4th ventricle, the pons tegmentum, which consists of the abducens nuclei; the pons base, which consists of the corticofugal fibers and also pontine nuclei; and also the center cerebellar peduncles.

Coronal ar through the Rostral Telencephalon. Number 1.17D is a ar taken in ~ the level the the decussation the the anterior commissure. Landmark structures include the head of the caudate nucleus, the anterior limb of the internal capsule, the globus pallidus and also putamen (important for managing motor functions). The anterior commissure, a fiber bundle connecting the right and left frontal lobes, deserve to be watched decussating (crossing the midline). The body callosum forms a thick tape of decussating nerve yarn located over the lateral ventricles. Below the telencephalon afferent nerve yarn from each eye decussate in the optic chiasm and also join uncrossed fibers to kind the optic tract.

Coronal section through the Midbrain-Diencephalon Junction. Number 1.17E is a section taken in ~ the level of the junction that the midbrain v the diencephalon. Notice that the airplane of section differs from those that the vault sections. At this level, a landmark framework of the diencephalon is the thalamus, which surrounding the third ventricle. The posterior limb of the interior capsule the end the thalamus from the bordering telencephalic structures (i.e., the globus pallidus and putamen). Lateral to the putamen is the insula while much more dorsomedially the body callosum overlies the cavities of the lateral ventricles. Below the 3rd ventricle space the red nucleus, substantia nigra and crus cerebri that the midbrain, which room the continuation of the inner capsule.

Section with the Midbrain. Figure 1.17F is a ar that mirrors the key midbrain nuclei which incorporate the tectum (superior colliculi) the periaqueductal gray, the red nuclei, substantia nigra and the cerebral peduncles.

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