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Nervous system —by Cyril Cao
I hope when you finished reading this dissertation, you will have a comprehensive understanding of the human nervous system. --Inscription I will expound my opinion from the following points.
PART 1 First things first, what is actually the nervous system was ? Let us view what the definition of the nervous system is. The nervous system is a system that plays a leading role in the regulation of physiological and functional activities in the body. It is mainly composed of nerve tissue and is divided into two parts: the central nervous system and the peripheral nervous system. The central nervous system in turn includes the brain and spinal cord, and the peripheral nervous system includes cranial nerves and spinal nerves. The nervous system is a complex functional system composed of neurons and glial cells, which is the material basis of psychological activity. Neurons are the basic functional units that make up the nervous system. Now, we know that the nervous system is composed of brain, spinal cord, cranial nerve, spinal nerve and vegetative nerve, as well as various ganglia. So, what functions and role in the human body do these organs have ?
The brain
The brain is divided into four parts: the telencephalon, the diencephalon, the cerebellum and the brainstem. The brain is also divided into two hemispheres, which manage different parts of the human body. The brain functions according to the principle of contralateral domination. In addition, the left and right brains also have their own division of labor. For example, the left brain is mainly responsible for language and logical thinking, the right brain is responsible for artistic thinking, and so on.
Spinal cord
The spinal cord is mainly a conduction pathway, which can transmit the external stimuli to the brain in time, and then transmit the commands issued by the brain to the surrounding organs in time to play the role of a bridge.
Cranial nerve
There are 12 pairs of cranial nerves, which mainly control the feeling and movement of the head and face organs. People can see the surrounding things, hear the sound, smell the smell, taste the taste, and have the expression of emotions, such as emotions, and so on, must rely on the function of these 12 pairs of cranial nerves.
Spinal nerve
There are 31 pairs of spinal nerves, including 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of phrenic nerves, and 1 pair of tail nerves. The spinal nerves are emitted by the spinal cord and primarily govern the senses, movements, and reflexes of the body and limbs.
Autonomic nerve
The autonomic nerves, also known as visceral nerves, are mainly distributed in the internal organs, cardiovascular and glands. Heartbeat, breathing and digestive activities are regulated by it. The autonomic nerve is divided into two types: sympathetic nerve and parasympathetic nerve. The two are mutually resistant and coordinated with each other to form a holistic organic whole, so that the visceral activity can adapt to the needs of internal and external environment.
Ganglion
The ganglion is mainly composed of a combination of the perinuclear body and the associated dendrites. The ganglia are often interconnected with other ganglia to form a complex ganglion system called the plexus. The ganglion provides points of attachment and mediation between different nervous systems within the body, such as the peripheral nervous system and the central nervous system.
PART 2 A summary and elaboration of the functions of the human nervous system.
1. The nervous system regulates and controls the co-functional activities of other systems, making the body a complete unity. 2. The nervous system adjusts the body's functional activities to adapt the body to the changing external environment and maintain the balance between the body and the external environment. 3. In the long-term evolutionary development of human beings, the nervous system, especially the cerebral cortex, has been highly developed, producing language and thinking. Human beings can not only passively adapt to changes in the external environment, but also actively understand the objective world and transform the objective world. To make nature serve humans, this is the most important feature of the human nervous system.
PART 3 How the nervous system works?
The functional activities of the nervous system are complex, but the basic mode of activity is reflection. Reflex is the response of the stimulation of the environment inside and outside the nervous system. The morphological basis of the reflection activity is the reflection arc. The basic composition of the reflex arc: sensor → afferent nerve → nerve center → efferent nerve → effector. If any obstacle occurs in any part of the reflex arc, the reflex activity will weaken or disappear. The reflection arc must be complete and indispensable. The spinal cord can perform some basic reflex activities.
PART 4 Ten interesting facts about the nervous system.
1. There are more nerve cells in the human brain than stars in the Milky Way. 2. If we arrange all the neurons in the body, it will grow about 965 kilometers. 3. There are only 100 billion neurons in your brain. 4. In the first year of the process, the brains of newborn babies almost tripled. 5. The left side of the human brain controls the right side of the body, and the right side of the brain controls the left side of the body. 6. Newborn babies lose about half of their nerve cells before birth. 7. There are approximately 13,500,000 neurons in the human spinal cord. 8. The nervous system can transmit nerve impulses at a speed of 100 meters per second, and in some cases, the transmission speed is about 180 miles per hour. 9. Compared with women, the gray matter of men's brain is 6.5 times that of women, but compared with men, the white matter of women's brain is 10 times that of white matter. 10. Your nervous system does not function properly without potassium and sodium ions. Vitamin B is equally important to the nervous system.
PART 5 CASE A Excessive intake of alcohol in the medical problems of the nervous system.
The central nervous system is the most sensitive organ to wine, and the more advanced the center is more sensitive to the effects of alcohol. For the central nervous system, ethanol acts as a sedative-hypnotic drug, and ethanol can enter the brain through the blood-brain barrier, and its inhibitory effect increases with increasing blood levels. The function of the cerebral cortex is to constrain the subcortical center. After a small amount of drinking, the cerebral cortex is first suppressed, and the subcortical center is excited by the fact that it is detached from the tube bundle. Therefore, the person appears to be restrained by the behavior of indulgence. If the amount of alcohol is further increased, the subcortical center is also suppressed and the state of excitement disappears. When the amount of alcohol is increased, the brain area of the awakening and the life center of the brainstem are also suppressed, causing disturbance of consciousness and breathing, cardiovascular inhibition, and even death. This is the reason why the performance after drinking is first stimulated and then suppressed.
The effects of ethanol on the central nervous system are summarized as follows:
The first phase: during the euphoric period, the speed and accuracy of all reactions are impaired, the ability to restrain is poor, emotional instability, irritability, and talkative.
The second phase: the obvious period of functional damage, unclear articulation, unstable gait, incomplete operation of various operations, and decreased self-control ability. These changes are related to the mood, environment and drinking habits at that time.
The third period: deep sleep coma, is a typical "drunken" period, ethanol blood concentration can reach 0.3%, affecting the life center, such as ethanol blood concentration of more than 0.4%, can die due to respiratory failure.
CASE B PVS In addition to retaining some instinctive neuroreflexes and the ability to metabolize matter and energy, vegetative ability (including cognitive ability to exist) has been completely lost without any active activity. The vegetative brainstem still functions, and when it delivers nutrients to the body, it can also digest and absorb, and can use these energy to maintain the body's metabolism, including breathing, heartbeat, blood pressure and so on. It also produces some instinctive reflexes to external stimuli, such as coughing, sneezing, and yawning. However, the body has no high-level neurological activities unique to human beings such as consciousness, perception, and thinking.
IN THE END How do you feel about the nervous system now ? |
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