The Human brain. Being the nerve center and regulator of all body functions, drugs must not be allowed to get into the brain
Have you ever considered how the brain works, the a mount of information being processed by this organ is huge and what is surprising is how orderly and efficient hey are being processed. Take for example one of the life practical example like driving a car. A lot of multi-tasking will be taking place like you position yourself well on the steering wheel, focused on the road and not sleeping, communicate with your feet, leg, hands and arms, knowing where the brakes are among very many things like listening to the radio, talking to your passengers. Can you imagine the kind of speed involved in processing such an amount of data all at the same time! While you look at these tasks as simple either because of your driving experience it may not be so if you bring the nerve center in the picture. In fact all these you are able to do them because of the proper functionality of your brain and so how does the brain work all these efficiently and perfectly?
Taking our example of driving as the bigger task, the brain will break it into smaller units like communicating, hearing, seeing etc. for them to be processed. A section of the brain will analyze movement of objects we see, the other part will be organizing the tasks in other words each part of the brain carry out specific task meaning that whenever a given task is to be done the right information is processed by that specific part of the brain. The other aspect of the brain is that in the event that a section of the brain is damaged then all the functions done by that section will not be done and that is why in an accident if the occipital lobe at the back of the brain is damaged then blindness occurs but other unaffected areas like seeing and movement continues to function normally because the job of seeing is highly compartmentalized, individuals who have lost one aspect of sight like the ability to see colors or to recognize faces, may still be able to do other visual tasks can you imagine being able to recognize people by hearing their voices but not being able to recognize them by their faces when you see them?
The advantage of this localization of function is when larger jobs are parceled out throughout the brain they all can be done at once. This decentralization of labor adds great speed to our ability to understand what is happening in the world around us, to analyze it, and then to generate appropriate responses. Dealing with information in this way is called parallel processing and it has been used by the computer scientists in the development of computers.
The human brain consists of several large regions, each of which is responsible for some of the activities necessary for life. These include the brainstem, cerebellum, limbic system, diencephalon, and cerebral cortex.
The brainstem is that part of the brain which connects the brain and spinal cord. This part of the brain is involved in coordinating many basic functions such as heart rate, breathing, eating, and sleeping.
The cerebellum coordinates the brain’s instructions for skilled repetitive movements and for keeping balance and posture.
The limbic system is involved in regulating emotions, motivations, and movement. It includes the amygdala and hippocampus, which is important for memory formation.
The diencephalon contains the thalamus and hypothalamus. The thalamus is involved in sensory perception and regulating movement. The hypothalamus is an important regulator of the pituitary gland, which directs the release of hormones throughout the body.
The cerebral cortex makes up the largest part of the brain mass and lies over and around most of the other brain structures. It is the part of the brain accountable for thinking, perceiving, and producing and understanding language. The cortex can be divided into areas that are involved in vision, hearing, touch, movement, smell, and thinking and reasoning.
The same ways specific areas of the brain control seeing and hearing, specific brain areas also control emotions, motivations, and movement. These functions are carried out by a part of the brain called the limbic system. The limbic system prevails on how we react to the world around us. Imagine a cool sunny day. You finish your work early and head to your favorite park for a leisurely walk with your dog. You are feeling so mellow that when the dog slobbers on your clean shirt, you merely scratch him behind the ears. Nonetheless on another day you have a completely different experience when you have to work late, traffic is up, and the dog runs away instead of coming to welcome you home. This time when the dog slobbers on you (after he finds his way home again) you shove him away and scold him.
The feelings you have in those two different situations are a result of your limbic system at work. The limbic system uses memories, information about how your body is working, and current sensory input to generate your emotional responses to current situations.
The limbic system is involved in many of our emotions and motivations, particularly those related to survival, such as fear and anger. The system is also involved in pleasurable activities necessary for survival, such as eating and sex. If something is pleasurable, or rewarding, you want to do it repeatedly. Pleasurable activities engage the reward circuit (or system), so the brain notes that something important is happening that needs to be remembered and repeated. The reward system includes several interconnected structures the ventral tegmental area (VTA), located at the top of the brain stem; the nucleus accumbens; and the prefrontal cortex). Neurons from the VTA relay messages to the nucleus accumbens and the prefrontal cortex. Information is also relayed back from the cortex to the nucleus accumbens and the VTA.
Most drugs of abuse activate the same VTA and nucleus accumbens neurons and that is why drugs produce pleasurable feelings to the drug user. And, because the feelings are pleasurable, the user wants to continue to experience the pleasure which they felt during previous drug use.
One of the reasons that drugs of abuse can exert such powerful control over our behavior is that they act directly on the more evolutionarily primitive brainstem and limbic structures, which can override the cortex in controlling our behavior.