Ataxia is a lack of co-ordination in the muscles. It is a symptom of damage to part of the central nervous system. Locomotor ataxia involves a lack of balance, or equilibrium. Patients must stand on a broad base, eyes open, or they will sway or even fall. The swaying increases if they shut their eyes. Ataxia has many causes, locomotor ataxia may be due to syphilis for example. Many diseases that damage the central nervous system may cause ataxia, including tumours of the cerebrum or cerebellum, some deficiency diseases, and diseases of the spinal cord. Ataxia may also result from overuse of such drugs as barbiturates or alcohol. Research Ataxia
The brain is the primary component of the nervous system, occupying the cranial cavity. Without its outermost protective membrane, the dura mater, the brain weighs an average of 1.4 kilograms, comprising about 97% of the entirecentral nervous system. The brain is connected to the upper end of the spinal cord (which connects through the foramen magnum of the skull) and is responsible for issuing nerve impulses, processing nerve impulse data, and engaging in the higher order thought processes. The brain is divided into three parts: the large cerebrum, the smaller cerebellum, and the brainstem leading to the spinal cord. The brainstem is also descriptively divided into the medulla oblongata, the midbrain, and the pons. The right hemisphere of the brain is a part of the cerebrum. The cerebrum, or forebrain, forms the bulk of the brain, formed of a large mass of white and grey neural fiber in the upper cranium. It is responsible for the higher thought processes (memory, judgement, reason), processing sensory data, and with initiating willful motor processes, such as voluntary muscle flexion. The cerebrum is composed of two lateral halves, or hemispheres, which feature a number of folds (gyri) and furrows (sulci) and which are connected in the middle at the medulla. Containing about a trillion neurons, the human brain is the most complex mechanism known, and its many functions are still largely a mystery. Research Brain
The brain stem operates automatically to control vital body functions such as breathing and blood pressure. It is a eight centimeter long stalk of nerve cells and fibres that joins the upper part of the spinal cord with the brain. The medulla oblongata is the lowest part of the brain stem and serves as the site of connection between the brain and the spinal cord. The pons is located in the brainstem, vertically between the midbrain and the medulla oblongata, and sagittally between the cerebellum and the pituitary gland. It is responsible for serving as a bridge between the cerebrum, the cerebellum, and the medulla oblongata. The brain stem is an extension of the spinal cord and acts as a highway for messages traveling from other parts of the brain to the spinal cord. The spinal cord and the brain form the central nervous system (CNS), which controls all of the body's basic functions such as breathing, the rate of your heart beat, and body temperature. Research Brain Stem
The cerebellum is a division of the brain, located below the cerebrum and in the posterior of the brain. The cerebellum features a central portion, called the vermis, and two side portions, or hemispheres - one on each side. It is the responsibility of the cerebellum to coordinate and modify the resultant activity of impulses and orders sent from the cerebrum. It does this by receiving information from nerve endings all over the body, such as the balance and equilibrium centers in the inner ear, and adjusts and fine tunes these actions by passing the regulating signals to the motor neurons of the brain and spinal cord. Damage to the cerebellum therefore results in loss of ability to maintain precise muscular coordination and fine cooperative actions of the motor processes (called ataxia). Research Cerebellum
The cerebrum is the upper and larger portion of the brain and occupies the whole of the dome of the skull. The cerebrum is descriptively divided into four section, or lobes, named for the cranial bones which they are nearest: the frontal lobe, the occipital lobe, the parietal lobe, and the temporal lobe. Cerebrospinal fluid, used to support the brain and buffer it, is transmitted to these lobes by means of lateral ventricles which project branches, or horns (cornu), into the frontal, occipital, and temporal lobes. The functions of each lobe are coordinated by connecting, or commissural, fibres. The frontal lobe is located behind the frontal bone and is responsible for voluntary motor coordination. It houses control areas for muscular control of the body and for coordinated rhythmical movements of the head and throat, such as in chewing, licking, and swallowing. The frontal lobe also contains the higher thought processing centers of memory, reasoning, and associative conceptualizing.
The occipital lobe is located just in front of the occipital bone and contains the centers responsible for sight. Damage to the occipital lobe therefore often results in vision impairment. The parietal lobe is located in the upper, middle part of the brain, next to the parietal bones. It houses the control centers for processing impulses related to the sense of touch. Temperature, texture, size, shape, and weight are analyzed and processed here. The temporal lobe is located on the side of each hemisphere of the brain, next to the temporal bone, and houses areas for the processing and correlation of auditory (hearing) and olfactory (smell) senses. Damage to this section of the brain can result in deafness, auditory hallucinations, and other hearing disorders. Research Cerebrum
The functions of each lobe of the cerebrum are coordinated by connecting, or commissural, fibres. The largest and densest of these is the corpus callosum, a broad, thick band which connects the two hemispheres and connects through branches to the rest of the surface, or cortex, of the cerebrum. The two smaller commissural fibres are the anterior commissure, which contains olfactory fibres as well as other temporal connections, and the hippocampal commissure which runs transversely below the rear of the corpus callosum and is specifically related to the olfactory centers of the brain. The corpus callosum features three general sections: the front section, which broadens and extends downward in the front, called the genu, the middle section, or trunk, and the rounded posterior portion, called the splenium. The genu extends downward to the structure known as the rostrum, and from there to the thinner lamina terminalis. Research Corpus Callosum
The longitudinal fissure runs down along the longitude of the cerebrum, separating the left and right hemispheres. It is interrupted in the intermediate region by the corpus callosum, which connects the two hemispheres. Research Longitudinal Fissure
Physotigmine is an alkaloid derived from the Calabar Bean. It has little effect on the cerebrum, but acts strongly on the vital centres in the medulla, and on the spinal cord where it produces feebleness of muscular movement, and slightly affects sensation. It was used in medicine where it was given to relieve tetanus and to antagonise the action of atropine and to relieve ocular tension. Research Physotigmine
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Gyrencephala
