Cerebrum system

The barbiturates are effective against convulsions induced experimentally from all central locations, the cerebrum, medulla, or spinal cord. They may be used clinically as well as experimentally to suppress most, if not all, varieties of convulsions of central origin (3). Since they are effective in the prevention of the tremors, tonic and clonic convulsions, and in the restoration of normal respiration from the Cheyne-Stokes type, produced by chlordan, it appears that these symptoms may have their origin in the central nervous system. 

The brain is the integrative portion of the nervous system that serves to receive, process, and store sensory information and then plan and orchestrate the appropriate motor response. It is divided into several anatomically and functionally distinct regions (see Table 6.2). The forebrain consists of the cerebrum, basal ganglia, thalamus, and hypothalamus. The midbrain, along with the pons and the medulla of the hindbrain, composes the functional region referred to as the brainstem. The cerebellum is also considered a component of the hindbrain but is functionally distinct from the brainstem. 

It may be noted that the retina represents an outlying portion of the brain itself. It arises as a protrusion from the prosencephalon (anterior portion of the cerebrum), and, being a constituent part of the brain, presents the same anatomical and physiological problems as does the central nervous system elsewhere. The more or less complete spatial separation of the synapses from the cell bodies makes the retina eminently suitable for finding out whether a known biochemical constituent is located in the cell bodies, axons, dendrites or at the synapses, and the information so obtained may perhaps be applicable to other parts of the nervous system, where the cell bodies and the synapses are all too intimately mingled for a proper analysis. 

As we move forward, it will prove helpful to get some basic aspects of the human nervous system in place. An enormous amount of work has gone into making associations between brain anatomy and function. Starting with the three main parts of the brain, we know that the cerebrum is the seat of consciousness. It is divided into two hemispheres, which are linked by the corpus callosum. In a very general sense, the left hemisphere is associated with intellectual and the right hemisphere with emotional responses. Within the cerebrum, one can associate a number of brain areas (the prefrontal, frontal, temporal, parietal, and occipital lobes, for example) with functions including vision and hearing. One can make crude maps in which function is mapped onto brain structure. 

The central nervous system consists of the brain and spinal cord. The average adult brain weighs 1250-1380 grams. The brain is divided into three gross parts the brainstem, the cerebrum, and the cerebellum. Structurally, the brain may be likened to a bouquet of flowers with the cerebrum (as two cerebral hemispheres) blossoming outwards above the brainstem the cerebellum is attached at the back of the brainstem. 

Figure 4.4 General structure of the brain the central nervous system consists of the spinal cord and the brain. The brain consists of the brain stem (medulla oblongata, cerebellum, pons, mesencephalon, diencephalon) and the cerebrum (cerebral hemispheres, subcortical white matter, basal ganglia).

Tire anatomy of the brain is quite complex, and only a few terms will be defined here. Tire cerebrum, which is made up of two hemispheres, accounts for the largest part of the brain. Tire deeply folded outermost layer, the cerebral cortex, consists of gray matter, a mass of cell bodies, and fine unmyelinated nerve fibers. Beneath this lies a layer of white matter made up of myelin-covered axons connecting the cerebral cortex with other parts of the brain. Tire two cerebral hemispheres are connected by the corpus callosum, a band of 2 x 108 nerve fibers. Remarkably, these fibers can be completely severed with a relatively minimal disruption of the nervous system. In the past the corpus callosum was sometimes cut to control almost incessant epileptic seizures that could not be prevented by drugs. The "split-brain" patients suffered relatively little disability as long as both eyes functioned normally. Studies of these patients provided some insights into the differing functions of the two hemispheres of the cerebrum.395... 

In humans and other more developed animals, most nerve cells are located in the brain and in the spinal cord, which together make up the central nervous system. The brain acts to process and integrate information. It is composed of several parts, the thinking portion of which is composed of two hemispheres at the top and front of the brain, called the cerebrum. This part of the brain is covered with a thin layer of gray matter called the cerebral cortex. 

Figure 5.9 The human olfactory system. (A) Section through the nose. (B) Section through the cribriform plate. (C) The olfactory pathway to the cerebrum (forebrain). This shows the pathway of olfactory sensation. Nasal stimulation begins at the cilia of the olfactory receptor cells located at the ends of the olfactory nerves. The olfactory nerves then carry the impulse to the cerebrum, resulting in the sense of smell.

Infection of the cerebrum, basal ganglia and cerebellum are observed less commonly. Depression is associated with other cerebral abnormalities but is uncommon in EPM. Protozoal infections in the cerebrum may be focal and associated with seizure activity and electroencephalographic abnormalities. Alternatively, asymmetric amaurosis (central blindness) and facial hypalgesia may be observed. Infection of the cerebellum results in cerebellar ataxia that is usually not associated with weakness or proprioceptive deficits. Involvement of the reticular activating system is also uncommon but may produce a narcolepsy-like syndrome in the absence of any other neurological signs. Occasionally, lameness that cannot be eliminated with nerve and joint local anesthesia may be the only evidence of a neurological deficit. 

Cocaine is used in medicine both as a local and a systemic remedy. Internally it is of value as a circulatory and respiratory stimulant and is occasionally of use as a cerebral stimulant or as a tonic. Its employment, however, in any condition which requires prolonged administration of the drug is fraught with so great danger of formation of a habit that it is rarely justifiable. In narcotic poisonings the simultaneous stimulation of the respiration, circulation, and cerebrum makes it a remedy of particular value. 

Stereotaxical injection of clodronate liposomes into the fourth ventricle of the central nervous system (CNS) of rats resulted in a complete depletion of perivascular and meningeal macrophages in the cerebellum, cerebrum, and spinal cord of these rats (20). These results confirm that, also, macrophages in the brain are accessible to liposomes if the latter are administered along the right route. 

Carcinoma Distinct margin with CNS anaplasia mitoses necrosis Cytokeratin (-I-) EMA (S) Cerebrum cerebellum meninges CNS frequent multiple masses systemic... 

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