- Naqser
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Posted by: Dwiggy
Posted by: Naqser
Well the trillions and trillions of cells don't got their own brains, duuh,
It's called a nucleus, einstein.
well no wonder, Einstein wasn't into biology, he was into mathematics
Nucleus:
In cell biology, the nucleus (from Latin nucleus or nuculeus, kernel) is found in all eukaryotic cells and contains the nuclear genes which form most of the cell's genetic material. Nuclei have two primary functions: to control chemical reactions within the cytoplasm and to store information needed for cellular division.The nucleus was discovered around 1833 by botanist Robert Brown.
Aside from containing the cell's genome, the nucleus contains certain proteins whose interplay is thought to regulate the expression of genes. Gene expression at the nuclear level involves complex processes of transcription, pre mRNA processing and the export of the mature mRNA to the cytoplasm.
The nucleus varies in diameter from 11 to 22.25 micrometres. It is enclosed by a double membrane called the nuclear envelope. The inner and outer membrane fuse at regular intervals, forming nuclear pores. The nuclear envelope regulates and facilitates transport between the nucleus and the cytoplasm, while separating the chemical reactions taking place in cytoplasm from reactions happening within the nucleus. The outer membrane is continuous with the rough endoplasmic reticulum (RER) and may be studded with ribosomes. The space between the two membranes (called the "perinuclear space") is continuous with the lumen of the RER. The nuclear face of the nuclear envelope is surrounded by a scaffold of filaments called the nuclear lamina.
Inside the nucleus is one or several nucleoli surrounded by a matrix called the nucleoplasm. The nucleoplasm is a liquid with a gel-like consistency (similar in this respect to the cytoplasm), in which many substances are dissolved. These substances include nucleotide triphosphates, enzymes, proteins, and transcription factors. There also exists a network of fibers in the nucleoplasm known as the
Genetic material (DNA) is also present in the nucleus, the DNA is present as a DNA-protein complex called chromatin. The DNA is present as a number of discrete units known as chromosomes. There are two types of chromatin: euchromatin and heterochromatin. Euchromatin is the least compact form of DNA, and the regions of DNA which constitute euchromatin contain genes which are frequently expressed by the cell.
In heterochromatin, DNA is more tightly compacted. Regions of DNA which constitute heterochromatin generally contain genes which are not expressed by the cell (this type of heterochromatin is known as facultative heterochromatin) or are regions which make up the telomeres and centromeres of the chromosomes (this type of heterochromatin is known as constitutive heterochromatin). In multicellular organisms, cells are highly specialised to perform particular functions, hence different sets of genes are required and expressed. Therefore, the regions of DNA that constitute heterochromatin vary between cell types
Brain: In animals, the brain, or encephalon (Greek for "in the head"), is the control center of the central nervous system. In most animals, the brain is located in the head close to the primary sensory apparatus and the mouth. While all vertebrate nervous systems have a brain, invertebrate nervous systems have either a centralized brain or collections of individual ganglia. The brain is extremely complex; the human brain contains 100 billion or more neurons, each linked to as many as 10,000 others[1]. This enormous number of interconnections, however, does not indicate intelligence.Early views on the function of the brain regarded it to be a form of “cranial stuffing” of sorts. In Egypt, from the late Middle Kingdom onwards, in preparation for mummification, the brain was regularly removed, for it was the heart that was assumed to be the seat of intelligence. According to Herodotus, during the first step of mummification: ‘The most perfect practice is to extract as much of the brain as possible with an iron hook, and what the hook cannot reach is mixed with drugs.’ Over the next five-thousand years, this view came to be reversed; the brain is now known to be the seat of intelligence, although colloquial variations of the former remain as in “memorizing something by heart”.A distinction is often made in the philosophy of mind between the mind and the brain, and there is some controversy as to their exact relationship, leading to the mind-body problem. The brain is defined as the physical, biological matter contained within the skull, responsible for all electrochemical neuronal processes. The mind, however, is seen in terms of mental attributes, such as beliefs or desires. Some suggest that the mind exists in some way independently of the brain, such as in a soul or epiphenomenon. Others, such as strong AI theorists, say that the mind is directly analogous to computer software and the brain to hardware.Three groups of animals have notably complex brains: the arthropods (insects and crustaceans), the cephalopods (octopi, squids, and similar mollusks), and the craniates (vertebrates)[2]. The brain of arthropods and cephalopods arises from twin parallel nerve cords that extend through the body of the animal. Arthropods have a central brain with three divisions and large optical lobes behind each eye for visual processing.[2]
The brain of craniates develops from the anterior section of a single dorsal nerve cord, which later becomes the spinal cord[3]. In craniates, the brain is protected by the bones of the skull. In vertebrates, increasing complexity in the cerebral cortex correlates with height on the phylogenetic and evolutionary tree. Primitive vertebrates such as fish, reptiles, and amphibians have fewer than six layers of neurons in the outer layer of their brains. This cortical configuration is called the allocortex (or heterotypic cortex)[4].
More complex vertebrates such as mammals have a six-layered neocortex (or homotypic cortex, neopallium), in addition to having some parts of the brain that are allocortex.[4] In mammals, increasing convolutions of the brain are characteristic of animals with more advanced brains. These convolutions provide a larger surface area for a greater number of neurons while keeping the volume of the brain compact enough to fit inside the skull. The folding allows more grey matter to fit into a smaller volume, similar to a really long slinky being able to fit into a tiny box when completely pushed together. The folds are called gyri, while the spaces between the folds are called sulci.
Although the general histology of the brain is similar from person to person, the structural anatomy can differ. Apart from the gross embryological divisions of the brain, the location of specific gyri and sulci, primary sensory regions, and other structures differs between species.
Invertebrates
In insects, the brain has four parts, the optical lobes, the protocerebrum, the deutocerebrum, and the tritocerebrum. The optical lobes are behind each eye and process visual stimuli.[2] The protocerebrum contains the mushroom bodies, which respond to smell, and the central body complex. In some species such as bees, the mushroom body receives input from the visual pathway as well. The deutocerebrum includes the antennal lobes, which are similar to the mammalian olfactory bulb, and the mechanosensory neuropils which receive information from touch receptors on the head and antennae. The antennal lobes of flies and moths are quite complex.
In cephalopods, the brain has two regions: the supraesophageal mass and the subesophageal mass,[2] separated by the esophagus. The supra- and subesophageal masses are connected to each other on either side of the esophagus by the basal lobes and the dorsal magnocellular lobes.[2] The large optic lobes are sometimes not considered to be part of the brain, as they are anatomically separate and are joined to the brain by the optic stalks. However, the optic lobes perform much visual processing, and so functionally are part of the brain
Vertebrates
The lobes of the cerebral cortex include the frontal (red), temporal (green), occipital (yellow), and parietal lobes (orange). The cerebellum (blue) is not part of the telencephalon. In vertebrates a gross division into three major parts is used.The telencephalon (cerebrum) is the largest region of the mammalian brain. This is the structure that is most easily visible, and is what most people associate with the "brain". In humans, the fissures (sulci) and convolutions (gyri) give the brain a wrinkled appearance. In non-mammalian vertebrates with no cerebrum, the metencephalon is the highest center in the brain. Because humans walk upright, there is a flexure, or bend, in the brain between the brain stem and the cerebrum. Other vertebrates do not have this flexure, and so comparing the locations of certain brain structures between humans and other vertebrates can be confusing.
Behind (or in humans, below) the cerebrum is the cerebellum. The cerebellum is mainly involved in the control of movement [5], and is connected by thick white matter fibers (cerebellar peduncles) to the pons.[4] The cerebrum and the cerebellum each have two hemispheres. The telencephalic hemispheres are connected by the corpus callosum, another large white matter tract. An outgrowth of the telencephalon called the olfactory bulb is a major structure in many animals, but in humans and other primates it is relatively small.
[Edited on 6/17/2006]