Cerebrum cortex

Fig. 9.4 Evolutionary change in the zones of vertebrate brains. Note that the figures are related here to the cerebrum cortex so that in man the hindbrain appears twisted downwards to allow for human upright stance.

Gross-him, n. cerebrum- -himrinde,/. cerebral cortex. -Industrie,/. = Grossgewerbe. grossl hrig, a. of age. 

The gray matter, which contains the cell bodies of neurons, is on the outer surface of the cerebrum and forms the cerebral cortex. The white matter, composed of the myelinated axons of neurons, is found underlying the cortex in the core of the cerebrum. These axons are bundled together according to function and organized into units referred to as tracts. The three types of tracts in the cerebrum are ... 

Figure 6.2 Frontal section of the brain. The cerebrum is composed of two types of tissue internal white matter and external gray matter which forms the cerebral cortex. Embedded within the cerebral hemispheres are other masses of gray matter, basal ganglia, and thalamus. The ventricles are filled with cerebrospinal fluid (CSF).

Named for the bones of the cranium under which they lie, the lobes are conspicuously defined by prominent sulci of the cortex, which have a relatively constant position in human brains. Each lobe is specialized for different activities (see Figure 6.3). Located in the anterior portions of the hemispheres, the frontal lobes are responsible for voluntary motor activity, speaking ability, and higher intellectual activities. The parietal lobes, which are posterior to the frontal lobes, process and integrate sensory information. The occipital lobes, located in the posterior-most aspects of the cerebrum, process visual information, and the temporal lobes, located laterally, process auditory information. 

The gray matter is composed of nerve cell bodies and unmyelinated intemeuron fibers. The location of the gray matter in the spinal cord is opposite to that of the brain. In the brain, the gray matter of the cerebrum and the cerebellum is found externally forming a cortex, or covering, over the internally located white matter. In the spinal cord, the gray matter is found internally and is surrounded by the white matter. 

The cerebrum is composed of four lobes covered by cerebral cortex frontal, parietal, temporal, and occipital (figure 2.9). The cortical surface... 

The anatomy of the brain and spinal column is very complex. The outer, most visible portion of the brain is known as the cerebrum. The cerebrum accounts for about 80% of the mass of the brain. Covered with a layer of grey matter known as the cerebral cortex, the cerebrum is divided into two hemispheres -left and right. 

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. 

BZ accumulates in the cerebrum following an intravenous injection in rats (Sawada et al, 1990). It is highly lipophilic and has a high degree of plasma protein and red cell binding. Steady state was reached in the cortex and caudate within 1 to 5 min. Binding to high-affinity m-AChRs is essentially irreversible for the first 6 h. 

Chronic Oral MRL for Methylmercury Hair levels are typically used as an index of exposure to methymercury. A number of studies report that hair mercury levels correlate with total intake levels and with organ-specific levels of mercury. Suzuki et al. (1993) analyzed 46 human autopsies in Tokyo, Japan and reported that hair mercury levels were highly significantly correlated with organ Hg levels in the cerebrum, cerebellum, heart, spleen, liver, kidney cortex, and kidney medulla, when the total mercury or methyl mercury value in the organ was compared with the hair total mercury or organic mercury, respectively. 

It should be noted that circadian rhythms in HT levels have also been found in the whole brain of the mouse94 and rat in the cortex of the rat96 and in the cerebrum and brain stem of the turtle97. 

The cerebrum is highly developed in humans. The cerebral cortex is a layer of neurons about 3-mm thick on the outer surface of the cerebrum. It is here that complex mental activities take place. 

Sensory information coming into the cerebrum is interpreted by specific areas of the cortex. Movement of body parts is controlled by another area of the cortex. The rest and the largest part of the cortex, which is neither sensory nor motor consists of association areas. It is here that complex aspects of behaviour such as memory, thought and language reside. 

Hunter and Russell 1954) - subsequently became known as Minamata disease " (see below), and is normally characterized by an extreme latent period of several months, or even years. These conditions start with nonspecific symptoms such as intention tremor, parenthesis, nausea, blurred vision, malaise, sensorial impairments and auditory disturbances, followed by ataxia and massive damage of the CNS. Characteristic is a concentric narrowing of the visual field (Harada 1995). At autopsy, the most conspicuous destructive lesion in the cerebrum was found in the anterior portions of the calcarine cortex. Less severe but similar lesions may be found in the post-central, pre-central and temporal transverse cortices. Secondary degeneration from primary lesions may be seen in cases with long-term survival. In the cerebellum, pathological changes occur deep in the... 

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