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Nervous System and Human Brain
Introduction
It is a common knowledge that the human nervous system is a complex system which coordinates all voluntary and involuntary actions in the organism of the human. It transmits signals from different parts of the body to the brain, and, therefore, is immensely important for homeostasis and human activities in general. Due to a particular importance of the nervous system, it is crucial to study how the nervous system in the human body works, how it is organized and maintained, and how it affects the human behavior. Therefore, the current paper seeks to describe the nervous systems structure and organization, discuss how the human brain has been studied through centuries, how it is organized, and how it influences the human behavior.
Nervous System Organization
It is generally accepted that the nervous system is formed out of coordination of the three main organs: human brain, the nerves, and the spinal cord. The spinal cord and the brain form the central nervous system, and the nerves form the peripheral nervous system. The brain, nerves, and spinal cords functioning are provided by neurons, the nerve cells. In fact, the main aim of the nervous system is to maintain the operations inside of the body parts in order to provide contribution to the decent life quality and homeostasis. Accordingly, the human nervous system directs and influences glands and muscles by sending impulses to different parts of the body. The salivary glands and the sweat glands are both controlled and regulated by the human nervous system. Moreover, it indirectly regulates other parts of the human body by adjusting the level of hormones, produced by the endocrine glands.
Central Nervous System
The neurons of the brain unite into neural networks to order and establish fast connections with the nearby neurons. As a matter of fact, the spinal cord connects the human brain to the peripheral nervous system. The work of the spinal cord is demonstrated by the neural pathways which govern human reflexes, the automatic responses to different stimuli. An ordinary spinal reflex and its pathway rely on a single motor neuron and a single sensory neuron, which often maintain communication process through an interneuron. This pathway can be possibly projected by the knee-jerk response. Other example can be provided by the pain reflex.
The innermost and the oldest region of the brain is the brain stem, which is aimed to control the main life functions, such as attention, breathing, and motor responses. In this area is the medulla, the brain area responsible for breathing and heart rate. Above the medulla there is the spherical shape, the pons, which help to control the body movements and plays a crucial role in walking and keeping balance. There is also a narrow and long network of neurons near the pons and the medulla called the reticular formation, which is aimed to filter out the stimuli. This part of the brain plays a particularly significant role in sexual activity, eating, walking, and sleeping.
Above the brain stem, the parts involved in the processing of emotions and behavior are situated. The main role in regulating emotions and memory plays the limbic system. It is a brain part which is situated between the two cerebral hemispheres and the brain stem. It consists of the hypothalamus, the amygdala, and the hippocampus. Hypothalamus is situated under the thalamus and consists of many small areas of the brain, which are important for linking the endocrine system to the nervous system. One of its main roles is regulation of hunger, sex, thirst, body temperature, and creating the feeling of pleasure.
However, the key to extraordinary abilities of the human brain can be found neither in the presence of the abovementioned parts of the brain nor in its big size. It is the large cerebral cortex which makes human brain extraordinary, which is an outer layer of the brain which allows humans to use language, create tools, acquire different skills, and live in social groups.
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Peripheral Nervous System
The peripheral nervous system of humans consists of two vital components automatic and somatic. The automatic nervous system is aimed to control the muscles of internal organs and glands, and directly or indirectly influences the heartbeat, glandular activity, and digestion. Moreover, its substantial functions are arousing and expanding energy in the body. The somatic nervous system influences voluntary control over the skeletal muscles.
The main part of the peripheral nervous system is a sensory part which consists of the sensory neurons. These neurons monitor conditions of the body outside the spinal cord and brain. Moreover, they monitor the surrounding conditions of the body. As a matter of fact, these neurons are thin long cells which extend through the nerves to the spinal cord. Once the sensory neuron responses to some condition, it transmits impulses in order to communicate about that particular condition to the spinal cord or brain.
It has been discovered by scientists that the nervous system contains more than 100 billion neurons. These sells are made up of such parts as: a cell body, which has the nucleus and keeps the cell alive, a long fiber called the axon, which transmits impulses from the cell body to other cells and a branching fiber called the dendrite, which collects information from other cells and sends it to the soma. There are sells which have thousands of dendrites, and are grouped to transmit information from other neurons. Some axons can be very long, as they have to transmit signals from the spinal cord to feet of hands.
Studying of the Brain
For many centuries humans had no opportunity to reveal the secrets of their brain and explore it in a living condition. However, physicians observed that brain is strongly connected to the mind. They noticed that damage to the human brain could change human behavior, cause paralysis or numbness. Other physicians observed that damage of the left front part influenced speech, while damage of the back of the human brain caused problems with vision. This was when the human brain was gradually mapped.
Nowadays, scientists are able to stimulate chemically, electrically, or magnetically different parts of the brain. They are now able to read messages of individual neurons and estimate the brains activity. Such techniques are extremely important for psychology as they give scientists opportunity to understand human behavior, character, and the way of life.
One of the most clear and immediate approaches to studying the human brain remains the analysis of the human cadavers. In this analysis, the brain can be fully studied, but the disadvantage of the approach is that it cannot be applied to a living brain.
Other approach to studying the living human brain is through the brain lesions. Sometimes, the human brain can be damaged as a result of falls, strokes, accidents, tumors, or gunshots, which are called lesions. However, in some occasions, the brain may be also damaged through surgeries. Oftentimes scientists use animals to create lesions and study the effects of that lesion on their behavior. These lesions give scientists an opportunity to observe how the damage can influence the brain functions. For example, when a human experiences a stroke, a part of the brain is deprived of oxygen, which results in a death of neurons in this area. Therefore, sometimes strokes result in a lack of some particular ability, depending on the parts of the brain where the stroke happens.
Other scientific approach that is used in the brain studies is studying the electrical activity of the brain by firing the neurons. Other approach, which was used with animals before, is to put detectors in the human brain in order to study responses of the neurons. Research has shown that there are particular neurons, called feature detectors, situated in the visual cortex that can detect lines and edges, movement, and even faces.
Other, less invasive approach, widely used on humans is electroencephalography (EEG). It is an approach that detects the electrical activity which is produced by the neurons of the brain through the use of electrodes which are put around the head of the patient. This approach can tell if a person is awake, asleep, or anesthetize as the brain wave patterns are different in each of these states. It can also translate the waves produced when a patient is writing, reading, and speaking, which makes this approach useful for clear understanding of the brain abnormalities. A clear advantage of EEG is that the patient can move while the waves are being recorded, which is useful for measuring the brain activity in little children who sometimes have difficulties with keeping still. Moreover, following electrical impulses on the brain surface, scientists can see changes over a very short time period.
Conclusion
Having described the structure and organization of the nervous system, having discussed the brain organization and its studies, and how it influences the human behavior, one has come to the conclusion that the nervous system is formed out of coordination of the tree main organs: human brain, the nerves, and the spinal cord, which form central and peripheral nervous systems. The brain, as the main part of the nervous system, has been studied for centuries, and physicians started noticing that damage to the human brain could change human behavior, cause paralysis, or numbness, influence speech and thinking, and therefore, affect the mind. Nowadays, despite the fact that number of clinical approaches to studying the brain has increased, the brain is not yet fully studied.
