Anatomy of The human Brain

The human brain is the center of the human nervous system and is a highly complex organ. Enclosed in the cranium, it has the same general structure as the brains of other mammals, but is over three times as large as the brain of a typical mammal with an equivalent body size.

There is nothing in the universe to compare with the human brain. This mysterious three-pound squishy tissue controls all necessary functions of our physical body, receives information from the outside world and makes it understandable, and goes beyond that which is understandable to embody the essence of our mind and soul. Intelligence, creativity, emotion, love, memories are but a few of the many things the brain does. Most of the expansion comes from the cerebral cortex, a convoluted layer of neural tissue that covers the surface of the forebrain. Especially expanded are the frontal lobes, which are involved in executive functions such as self-control, planning, reasoning, and abstract thought. The portion of the brain devoted to vision is also greatly enlarged in human beings.

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The brain is very soft, having a consistency similar to soft gelatin or firm tofu. Despite being referred to as "grey matter", the live cortex is pinkish-beige in color and slightly off-white in the interior.  The cerebral hemispheres form the largest part of the human brain and are situated above most other brain structures. They are covered with a cortical layer with a convoluted topography. Underneath the cerebrum lies the brainstem, resembling a stalk on which the cerebrum is attached. At the rear of the brain, beneath the cerebrum and behind the brainstem, is the cerebellum, a structure with a horizontally furrowed surface that makes it look different from any other brain area

The nervous system is a very complex system in the body. It has many, many parts. The nervous system is divided into two main systems, the central nervous system (CNS) and the peripheral nervous system. The spinal cord and the brain make up the CNS. Its main job is to get the information from the body and send out instructions. The peripheral nervous system is made up of all of the nerves and the wiring. This system sends the messages from the brain to the rest of the body.

The human brain is divided into two hemispheres, and within each of these hemispheres are found four lobes or sections: the frontal lobe, the parietal lobe, the occipital lobe and the temporal lobe. These lobes perform their own specific functions.

The frontal lobes of each hemisphere are located just behind the forehead. Among other things, they are partially responsible for language, motor function, judgment, problem solving, impulse control, reasoning, memory and the ability to plan and fulfill plans. Behind the frontal lobes lie the parietal lobes. These lobes are the least understood among the four, but are the principal integrators of sensory information such as taste, pain and temperature. They are also responsible for reading and arithmetic. The occipital lobes lie in the back and are related to visual processing, so much so that injury to an occipital lobe could cause blindness. Lastly, the temporal lobes are found under the parietal lobe and are responsible for memory, hearing, perception and recognition.

 The olfactory, optic, oculomotor and trochlear cranial nerves are located in the anterior portion of the brain. The trigeminal, abducens, and facial nerves arise in the pons. The vestibulocochlear nerve arises in the inner ear and goes to the pons. The glossopharyngeal, vagus, accessory and hypoglossal nerves are attached to the medulla oblongata.

 Apart from the scalp and skull there are three other layers inside the skull that encase and protect your brain. These coverings together are the meninges, and consist of the "Dura Mater", the "Arachnoid", and the "Pia Mater". Not surpisingly, like most medical nomenclature it is derived from Greek, even though the meninges were not identified and labelled until the Renaissance.

The Arachnoid or "spider-like" covering is the middle layer of the three meninges and is laced throughout with blood vessels, looking like a spider's web, hence its name. The arachnoid is secured to the dura mater and therefore closely adhres to it, in contrast to being more separated from the pia mater. The space between the pia mater and arachnoid is where the cerebro-spinal fluid (CSF) is largely contained and called the sub-arachnoid space. It is this sack of fluid that protects or at least minimizes damage to the brain from impacts to the skull.

The Dura mater or "Tough Mother" is the outside fibrous leather-like layer that truly protects the brain. Apart from actually encasing the brain, it is also fused to the skull at a number of points, and therefore also restricts and anchors the movement of the brain within the skull. The dura mater also separates and partitions the brain as a more efficient method of securing the brain to the skull, with each of the two hemispheres, and the cerebellum being encased separately

Blunt force trauma to the head, often causes a rupture of the vasculature of the meningeal layers, or a brain bleed. The name of the brain-bleed often depends upon the location of where the blood pools. Thus, during a subarachnoid bleed, the ruptured blood vessel(s) leak into the space between the pia mater and arachnoid, and frequently can be detected by a pink tinge to the CSF. Conversely, a subdural hematoma, is a pooling of blood inthe tight space between the dura mater and the arachnoid, which can cause damage to the brain by swelling and putting pressure upon it. If caught early enough it is easily rectified by drilling a hole to this space and draining it, relieving the pressure and allowing the brain to come back to normal.

One of the other frequently heard conditions is meningitis, which is a viral or bacterial infection of the meninges, which causes them to become imflamed. Viral infections often subside withini a few days, but the bacterial infections can induce seizures and become life threatening. Although caused by a number of common bacteria, most meningitis can be treated with standard anti-biotics. Frequently meningitis has originated from other tissue immflamation like sinusitis or imlammation of the sinuses. The big fear behind bacterial meningitis is that it can be contagious and passed on in the same fashion as a cold or flu might be.

 The entire blood supply of the brain and spinal cord depends on two sets of branches from the dorsal aorta. The vertebral arteries arise from the subclavian arteries, and the internal carotid arteries are branches of the common carotid arteries. The vertebral arteries and the ten medullary arteries that arise from segmental branches of the aorta provide the primary vascularization of the spinal cord. These medullary arteries join to form the anterior and posterior spinal arteries

In general, the left hemisphere of the brain is responsible for language and speech and is called the "dominant" hemisphere. The right hemisphere plays a large part in interpreting visual information and spatial processing. In about one third of individuals who are left-handed, speech function may be located on the right side of the brain. Left-handed individuals may need special testing to determine if their speech center is on the left or right side prior to any surgery in that area.

Aphasia is a disturbance of language affecting production, comprehension, reading or writing, due to brain injury – most commonly from stroke or trauma. The type of aphasia depends on the brain area affected.

 Many scientists are applying this conception of the mind to the brain's various sub-functions, such as memory. According to this model, memory is a holistic neural activity, involving many different areas and processes of the brain in an intricately choreographed dance. Memory has been variously characterized as "a process of information retention in which our experiences are archived and them recovered when we recall them"; memories as "enhanced patterns of neuronal interconnections which are subject to continual change" ; and memory stores as "multi-modal networks of neurons throughout the nervous system"  which "require that nervous cells form new interconnections and produce new protein molecules

 Neurons are nerve cells that transmit nerve signals to and from the brain at up to 200 mph. The neuron consists of a cell body (or soma) with branching dendrites (signal receivers) and a projection called an axon, which conduct the nerve signal. At the other end of the axon, the axon terminals transmit the electro-chemical signal across a synapse (the gap between the axon terminal and the receiving cell). The word "neuron" was coined by the German scientist Heinrich Wilhelm Gottfried von Waldeyer-Hartz in 1891 (he also coined the term "chromosome").

The axon, a long extension of a nerve cell, and take infromation away from the cell body. Bundles of axons are known as nerves or, within the CNS (central nervous system), as nerve tracts or pathways. Dendrites bring information to the cell body.

Myelin coats and insulates the axon (except for periodic breaks called nodes of Ranvier), increasing transmission speed along the axon. Myelin is manufactured by Schwann's cells, and consists of 70-80% lipids (fat) and 20-30% protein.