CHAPTER 1: WHAT IS A BRAIN TUMOR Brain tumors are tumors that grow in the brain. A tumor is an abnormal growth caused by cells reproducing themselves in an uncontrolled manner. There are two types of tumors; benign (meaning harmless) and malignant (meaning cancerous). These meanings change, however, when referring to tumors in the brain. Benign brain tumors: A benign brain tumor consists of benign (harmless) cells and has distinct boundaries. Surgery alone may cure this type of tumor. Malignant brain tumors: A malignant brain tumor is life-threatening. It may be malignant because it consists of cancer cells, or it may be called malignant because of its location. In other words, a brain tumor composed of benign cells--but located in a vital area--is still considered malignant, because they are very dangerous anyway. A malignant brain tumor made up of cancerous cells may spread or seed (metastasize) to other locations in the brain or spinal cord. It can invade and destroy healthy tissue so it cannot function properly. Malignant tumors grow the way a plant does, with "roots" invading various tissues. Or, they can shed cells that travel to distant parts of the brain. Some cancerous tumors, however, remain localized. Malignant brain tumors seldom metastasize outside the brain and spinal cord. Often, the damage done by brain tumors is due to their size. Because the skull is bone, it cannot expand to make room for even a small mass growing within it. As a result, the tumor presses on and displaces normal brain tissue. This pressure may damage or destroy delicate brain tissue. This pressure causes many of the symptoms of a brain tumor. Sometimes, a tumor may cause blockage of fluid that flows around and through the brain. This blockage can also create increased pressure. Then it is possible to separate the brain tumors again; there are tumors starting in the brain, which are called primary brain tumors, and there are Metastatic brain tumors, which are tumors consisting out of cancerous cells formed elsewhere in the body and spread to the brain.
CHAPTER 2: WHAT IS THE BRAIN, WHAT DOES IT EXIST OF, AND WHAT EFFECT HAS THE LOCATION ON THE TUMOR
The brain is simply a soft, spongy mass of nerves and supportive tissue. The bas eof the brain is connected to the spinal cord, and the nerves that extend out of the brain and spinal cord into various parts of our body, act together to send information to the brain and send instructions from the brain. The brain itself is divided as well, there are different, parts of the brain responsible for different things, in this chapter the different tasks and places are described.
Cerebrum - This contains the largest part of the brain. It consists out of two halves, the right and left hemispheres. The right hemisphere controls the left part of the body, and the left hemisphere takes care for the right part of the body. The outer part of the cerebrum, called the cerebral cortex, is made up out of grey matter, but the inner part though is white matter. In addition, there are areas of grey matter, called basal ganglia. Grey matter is composed of nerve cells. These cells control brain activity. White matter is composed of myelinated nerve cell axons that carry information between nerve cells in the brain and spinal cord. The hemispheres are divided up in four lobes again, and each lobe is responsible for specific things in the body.
Frontal lobe - Responsible for voluntary muscle movements. The frontal lobe of the dominant hemisphere controls speech and writing. (The dominant hemisphere is the opposite side of the side you use most, left-handed means the right hemisphere is dominant)
Parietal lobe - The parietal lobe receives and interprets sensations, such as pain, temperature, touch, pressure, size, and shape. Other activities of this lobe are hearing, reasoning, and memory.
Temporal lobe- Involved in understanding of sounds and spoken words, further involved as well in emotion and memory.
Occipital lobe – Involved in understanding visual images and the meaning of written words.
Cerebellum - This is the second largest area of the brain, also consisting out of two hemispheres, these are connected by the vermis. The cerebellum, together with the thalamus and cerebrum, controls skilled muscular co-ordination, including walking and speech (words doctors would use for this are gait and articulation)
Pons - The pons co-ordinates the activities of the cerebrum and cerebellum by relaying them and the spinal cord.
Medulla Oblongata - The Medulla Oblongata controls respiration, heart beat and vomiting. It connects the brain with the spinal cord.
Ventricles and choroid plexus - There are four connected ventricles (cavities) in the brain, inside each there are structures called choroid plexus.
Choroid plexus forms spinal fluid, which flows through the ventricles and the subarachnoid space surrounding the brain and spinal cord.
There are two lateral ventricles, one in each cerebral hemisphere. The third ventricle is beneath the corpus callosum and surrounded by the thalamus. The fourth ventricle is between the hemispheres of the cerebellum. It is an expansion of the central canal of the medulla oblongata.
The cerebral aqueduct, called the aqueduct of Sylvius, is a narrow canal connecting the 3rd and 4th ventricles.
Hypothalamus - The hypothalamus makes up part of the wall of the third ventricle and is the base of the optic chiasm. It controls water balance, sleep, temperature, and blood pressure. The hypothalamus co-ordinates patterns of activity and controls emotions. It is also the control centre for the pituitary gland.
Thalamus - The thalamus surrounds the third ventricle. It monitors input from the senses and acts as a relay station for the sensory centre of the cerebrum.
Limbic System - The limbic system, together with the hypothalamus, controls hunger, thirst, emotional reactions, and biological rhythms. In addition, it co-ordinates complex activities requiring a sequence of performance steps.
Brain stem - The brain stem controls basic functions, including blood pressure, heart beat, and respiration. It is the bottom-most portion of the brain, connecting the cerebral hemispheres with the spinal cord. There are several structures part of the brain stem:
- Pons Reticular Formation
- Medulla Oblongata Midbrain
Reticular Formation - The reticular formation is the central core of the brain stem. It controls consciousness, eating, and sleeping patterns, drowsiness, and attention. The reticular formation connects with all parts of the brain and brain stem. Midbrain - The midbrain is the short portion of the brain stem between the pons and the cerebral hemispheres. The midbrain is a relay centre for sight and hearing. When a brain tumor enters the brain and starts growing, it presses some other thing away (the part of the brain where the tumor is growing), which makes it impossible for that part of the brain to do its function the way it should do it. It will die or at least injure, depending on which part of the brain it is, the symptoms will differ as well. The parts of the brain all have their own function, and those parts of the brain bullied by the tumors can’t operate functional. Here will follow some examples of what the effects are when a tumor bothers those parts of the brain:
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