In this term paper we will be learning about the parts of the brain and the various tasks that the brain completes on a daily basis. While many of these functions and parts might be translated to a variety of creatures, for the purpose of this term paper, we are primarily going to be referencing human beings.
The Parts of the Brain:
The size and shape of every brain is slightly different. This also means it is not always easy to find the common features from one brain to another. Yet, scientists have discovered some interesting aspects of brain architecture that seems to apply no matter what type of species. So we are going to start looking at various parts of the brain, starting with the cellular level.
The brain is made up of the same type of cells that one finds in the nervous system. These cells are the glial cells and neurons. Glial cells perform a variety of functions, such as metabolic support, structural support, guidance of development and insulation. While this is all an important part of the brain, the most critical cells are considered the neurons. Why is this the case?
Because these cells are the ones that have the ability to target specific cells across long distances, allowing for messages to be relayed to all the organs of a body. There are six main regions within the brain.
Below we will discuss each of these areas and any associated functions:
1. Telencephalon:
Otherwise known as the cerebral hemispheres or cerebrum; it contains the cerebral cortex. This region is made up of two cerebral hemispheres and their various cortices, as well as the outer layers of gray matter and the internal layers of white matter.
2. Diencephalon:
Part of the forebrain consists of the hypothalamus; thalamus; epithalamus and sub-thalamus. Optic nerve attaches to this region. Within this region, there are multiple glands that control hormone delivery throughout the body, as well as control of visceral activities within other areas of the brain and the automatic nervous system.
3. Mesencephalon:
Known as the midbrain, associated with hearing, vision, sleep/wake, arousal, motor control and temperature regulation. This area is located below the cerebral cortex and above the hindbrain, so it is typically found in the center of the brain.
Contained within this area is the tectum, inferior and superior colliculi, cerebral peduncle, midbrain tegmentum, substantia nigra and crus cerebri. Considered part of the brainstem, this region is associated with motor system pathways, as well as playing a role in the motivation, excitation and habituation, while relaying information for hearing and vision.
4. Cerebellum:
Tightly folded layer of cortex, include four deep nuclei. Three lobes can be defined- the anterior lobe; the posterior lobe; and the flocculonodular lobe. In charge of precise motor control; calibrating the detailed movement’s form but it does not decide which movements to execute.
Involves feed forward processing, because there is little internal transmission between input and output during the signal processing. Also plays a part in motor learning, particularly if there are fine adjustments that must be made during the motor function.
5. Pons:
Part of the brainstem. Lies between the midbrain and the medulla oblongata, but is in front of the cerebellum. Regulates the change from inhalation to exhalation. Plays a role in generating our dreams. Deals with respiration, sleep, swallowing, hearing, bladder control, equilibrium, taste, facial expressions, posture, eye movement and facial sensation. Divided into two parts. Often associated with touch and pain for the face.
6. Medulla Oblongata:
Located in the hindbrain. Cone-shaped and responsible for various involuntary functions, including vomiting and sneezing. Contains respiratory, cardiac, vasomotor and vomiting centers. Deals with heart rate, breathing and blood pressure. Connects higher levels of the brain to the spinal cord. Functions include regulating various reflexes, including the swallowing reflex.
Throughout these various regions, there are multiple smaller areas and parts, including various nerves that make up each of these distinct areas. There is plenty of overlap between regions, but the most important thing to take away is that the brain works harmoniously, despite all the various regions that must be part of the process to get anything accomplished.
The other important takeaway is that most of these things happen nearly instantaneously. It takes much longer to describe these functions than it does for the brain to actually execute them.
There are multiple ways for these messages within the brain to be relayed. Ultimately, these processes occur on a cellular level and are the building blocks of the other major components of the brain. Keep in mind, the components are smaller parts of these regions and these components have smaller parts that are part of them. The brain is very complex, as we will continue to see.
Below is information about each of the components found in the brain:
1. Cerebral Cortex:
Outer layer of gray matter found in the cerebrum; generally classified into four lobes- the occipital, frontal, parietal and temporal.
2. Medulla:
Contains small nuclei, which along with the spinal cord, contain a wide variety of involuntary motor functions, including vomiting, digestion practices and vomiting. It is also a source of sensory functions as well.
3. Pons:
Located within the brainstem, it is directly above the medulla. It controls voluntary but simple acts, including respiration, bladder function, eye movement, posture, facial expressions, swallowing, sleep and equilibrium.
4. Hypothalamus:
A region of the brain at the base of the forebrain, it is engaged in involuntary or at least partially voluntary actions. Some of these are eating and drinking, release of some hormones and sleep/wake cycles.
5. Thalamus:
Responsible for relaying information and motivation back and forth between cerebral hemispheres. This also includes the subthalamic area, which is defined by its action generating systems, including behaviours such as eating, defecation, drinking and copulation.
6. Cerebellum:
This is the modulation center for the outputs of brain systems, regardless of whether they are motor or thought related. Muscle coordination is an example of how this part functions. While it does not provide instant precision, this is where we really do our learning. In fact, this part accounts for almost 10% of the brain’s total volume and at least 50% of all neurons are held within this structure.
7. Optic Tectum:
This part controls actions that are directed toward various points within space, most commonly related to visual stimulus. It also directs movements involving reaching and other object-directed acts. While it does receive visual input, this area also receives inputs from the other senses when it relates to directing various actions. It is also identified as part of the midbrain area.
8. Pallium:
Found on the surface of the forebrain, this layer of gray matter is involved in smell and spatial memories. However, this area of the brain consists of multiple folds that increase the surface area of the pallium. As a result, the amount of information that can be processed and stored increases with the increase of folds.
9. Hippocampus:
Only found in mammals and is involved in complex events, such as navigation for various animals.
10. Basal Ganglia:
An interconnected group with the forebrain. Primary function is to make action selections and this area can send inhibitory signals throughout the brain to stop various motor behaviors. Reward and punishment have the greatest effect in this area, by altering connections in this part of the brain.
11. Olfactory Bulb:
Processes olfactory sense signals and then sends the output to the pallium for combining with other sensory information. Smaller in humans than other vertebrates, although primates also have a smaller bulb.
The brain is made up of multiple parts. While it seems that there is some cross over in terms of what each area is responsible for, this redundancy also makes it possible for the brain to bounce back from various injuries because other areas can be reassigned to take over functions for the area that has been damaged.
When looking at brains across a variety of species, one thing that becomes clear is that size and shape do play a part in the processing power of one brain versus another. For instance, the size and shape of forebrain result in dramatic difference in terms of what a creature might be able to do with their brain. Now let us spend some time learning about the development of this amazing control and processing center.
Brain Development:
The development of our brains is something that fills many individuals with awe. This complicated and high functioning organ starts as a simple swelling of the nerve cord before growing into the complex organ that gives us the ability to do so much, including appreciating art, understanding science and mathematics, as well as have feelings, morals and ethics.
As the brain develops during the embryonic stage, it builds an extremely complex array of connections through different areas. Neurons are created by stem cells in specific zones, then begin their migration to reach their final destinations. Once they are in position, they begin to sprout axons, navigating through the brain via branching and extensions. Eventually, they reach their targets with the tips of their branches and these tips form the synaptic connections necessary for the brain to exert its control over the body.
Excessive numbers of these neurons and synapses are created, but the unneeded ones are eventually pruned away.
Yet this growth and creation of the brain and nervous system requires more than just the creation of a few synapses. During the embryotic stage, a narrow strip of ectoderm is left running down the back. Eventually, this narrow stripe will become part of the new spinal cord housed in the spinal column in your vertebrae.
This stripe of ectoderm first becomes the neural plate, which eventually folds inward to create a neural groove. The lips of this groove merge together to enclose the neural tube. What is a neural tube? It has been described as a hollow cord filled with cells and a fluid filled ventricle, which can be found in the center of the neural groove. The front of this tube swells to form the parts that will eventually become the forebrain, midbrain and hindbrain.
Now that we have the early stage of the brain, big changes start occurring. The bulge that forms the forebrain begins to split into two vesicles. These will end up being the telencephalon and the diencephalon.
The hindbrain also splits in two parts, the metencephalon and the myelencephalon. All during the process, those neurons are branching out and making more and more connections. Still, those connections are on a cellular level, contributing the building blocks that become the gray and white matter that will end up folding into various parts and regions of the brain. Other cells will step in and blood vessels to feed these cells will also be created.
In nine months, this amazing organ will be ready to start learning, while continuing its growth pattern. While glial cells will continue to be produced throughout our lifetimes, neurons are primarily created during pregnancy and early childhood. As adults, we are limited in our ability to have new neurons generated. As a result, there can be irreversible damage to the brain when a large number of neurons are killed off.
There have been many debates about nature versus nurture when it comes to brain health and development. However, studies seem to suggest that both play a role. While genes may determine the shape of the brain and how it might react to experiences, the experiences themselves refine the matrix of synaptic connections within the brain itself.
Now we will examine how the brain’s electrical and chemical processes work during the process of making those connections.
It’s Electric – Understanding Electric and Chemical Activity in the Brain:
Within the brain, there are constant neurotransmitters at work. These are chemicals that get released at various synapses when the possibility of action actives them. Those neurotransmitters attach to special receptor molecules, modifying the electrical or chemical properties of those receptors.
Neurons release the same transmitter or combination of transmitters to all its synaptic connections. So neurons can be classified by their transmitters. Psychoactive drugs work on the principle that they are altering neurotransmitter systems.
There are two types transmitters that are found most frequently in the brain. One is glutamate and gamma- aminobutyric (GABA). Glutamate is known for its excitatory properties on target neurons, while the gamma-aminobutyric is associated with inhibitory effects.
For example, anesthetics reduce glutamate’s effects, while GABA is enhanced by means of tranquilizers. As a result, it is important to remember that each neurotransmitter has its own distinct properties and those properties can be altered through a variety of substances.
Other chemical neurotransmitters are available within the brain, but they are used in some very limited areas and are dedicated to very specific functions. An example is serotonin, which comes exclusively from a very small are of the brainstem known as the Raphe nuclei. Serotonin is the target of diet drugs and antidepressants.
Another transmitter known as norepinephrine is responsible for arousal and produced in the locus coeruleus, which is also around the brainstem. There are two other transmitters that have multiple sources within the brain, acetylcholine and dopamine, but they are not as widely distributed as GABA and glutamate.
The brain sends messages via a chemical function, but if the right combination does not occur, the messages will not get sent. Taking in drugs and other substances can also alter the type of message that is sent. For instance, we see that individuals taking in large amounts of alcohol or other drugs can change the production of different transmitter, resulting in a lowering of inhibitions and blocking the judgement center of the brain from doing its job.
Yet, as we have learned from other sections of the body, humans have a certain amount of electrical charge. In fact, we create electrical fields. This is also true within the brain. There are multiple electrochemical processes and the side effect of them is the electric fields they generate.
If a large enough number of neurons are firing at the same time, the electric field they create can actually be detected outside of the skull. Medical professionals use an EEG or MEG machine to record these electric fields. The results have shown scientists that even while we are asleep, the brain is constantly active.
Imagine a machine that is constantly humming, processing billions of pieces of information in a matter of seconds. This is what the brain is constantly doing throughout the day. At night, when we are resting, the brain is directing traffic within the body.
Tissue repairs, muscle repairs and other necessary functions that allow our bodies to function throughout the day are completed while we sleep. This is the time when the brain is supposedly at rest. When we are awake, there is even more for the brain to complete, process and make decisions about.
So what does all of this activity look like on an EEG? Simply put, it appears as a variety of wave lengths. Delta waves are large and slow, appearing most frequently during sleep. Alpha waves are a faster version of delta waves and they might appear slightly shorter.
However, it has been noted that alpha waves appear when we are awake, but not necessary attentive on a specific task. The charts look chaotic with spikes when we are actively engaged in a task or project that has our full attention.
Yet when a brain is damaged by seizures, the EEG can show a chart with almost pathological levels of electrical activity. This is because the brain’s inhibitory mechanisms are not functioning. As a result, the pattern shows large waves and various spike patterns of an unhealthy brain.
A seizure, in effect, causing the electrical timing of the brain to be off and so the brain struggles to realign itself after a seizure is over. This is a particular area of study for researchers, because it is important to understand both how the electrical activity effects the brain and how to create medicine that assists in the process.
Throughout this basic study of the brain, we have learned about just a few of the complex processes that occur every second. It not only assists us to make decision and be insightful, the brain is also directing all the other myriads of functions occurring within the body itself. This includes fine motor movements, breathing and digestion, just to name a few of the processes.
Within our brains, however, there is another unique process that occurs apart from any other in our body. It is metabolism.
The Brain’s Metabolism:
The body has a metabolism, which is the rate at which molecules are either prepared for storage or used for a specific immediate use. Molecules can also be made into by-products through these chemical processes. For example, our bodies use metabolism to either create or burn fat. While it might be easy to assume that metabolism is constant throughout our bodies that is not really the case.
Our brains actually run at a different metabolism that is apart from the rest of the body’s metabolism. This makes sense if you think about it. The brain must do so much processing and movement of messages throughout just a few minutes that it cannot afford to have a metabolism geared to the same rate as the rest of the body.
Glial cells control the chemical composition of the brain’s fluid, even down the ion and nutrient levels. The reason for this particularly high level of control is that the brain is constantly consuming large amounts of energy, even though the brain itself is relatively small. Most of this energy is used to maintain those electrical charges.
Therefore, the brain maintains a separate metabolism to adjust for its very unique needs. While most of its energy comes from glucose, the brains also use ketones, fatty acids, lactate and acetate. There is still some discussion about whether or not amino acids can be added to this list as well.
The Brain: Our First Personal Computer:
When we think of information processing, our first thoughts go to our computers. Most of us own a version of a smartphone, which is literally a hand-held computer. The processer in our phone can handle multiple tasks at our request, including making a call while getting us directions to our destination and notifying us that our best friend just posted to Instagram.
Yet the processing power of this one small device is not even a portion of the processing power found in our own heads. So how did this whole understanding of the brain as a processing center get started? In the 1940s, computers and mathematical information theory were being developed. Scientists looked at the way these machines were operating and they wondered if the same patterns could be applied to the brain, thus giving us a better understanding of how it functioned.
As a result, a new field of study known as computational neuroscience was created. Simply put, the processing of the brain was originally thought of in terms of algorithms and the flow of information. Science, however, has begun to use collected data to move into a more realistic understanding of how it all functions.
One of the early contributions came from a paper that examined how the various visual responses of the retina’s neurons and optic tectum of frogs. The study concluded that the neurons in the tectum essentially combined elementary responses. This study was completed with frogs and they found that the tectum became a bug perceiver that allowed the frog to find food.
Other investigations have led to a growing body of knowledge that shows how the brain is able to produce increasing complex responses, despite distance between the various parts of the brain. Cells can have a wide variety of responses to what we see, even if they appear to be unrelated to the actual sense of vision, including memory responses and abstract cognition types.
To understand how all these response patterns work, scientists have begun to put together mathematical models, using a variety of powerful computers. Some of these models are abstract, meaning that they focus more on the concept of neural algorithms versus how they are actually implemented in the brain. Others try to use the data to better understand the biological properties of the actual neurons themselves.
Still, none of these models have been able to completely capture the full function of how the brain operates. Then you have to understand that these models are based on what groups of neurons are accomplishing. When you get down to a single neuron, you find something that is unique and incredibly complex.
These neurons are able of completing the equivalent of multiple computations on their own. Current methods of computing brain activity can isolate a few dozen neurons and their actions at best. Clearly, there is much more that will be learned about the brain’s processing power as time goes on.
The Human Brain Project has begun to the process of building a realistic computational model of not just one area of the brain, but the whole thing. Whether they succeed or not remains to be seen, but it is clear that they are moving in a direction to better understand this unique control center and how it actually manages to do all that these neurons and cells do every single day.
A variety of functions completed by the brain that involve multiple areas of the brain. As you will see, these working relationships are precise and extremely accurate, guaranteeing that what needs to happen does so, every time.
One of the first areas of brain function that is of interest to scientists is how the brain processes all the sensory information it receives. Remember, the brain is not just receiving visual or auditory signals. It is receiving both and so much more from the other senses. All this information needs to be combined into one complete picture.
Thus, the brain takes in all these signals and processes them, before then sending the signals to the area of the brain that handles that particular signal. Eventually, everything is reintegrated and the brain makes decisions and prompts actions based on that information. What scientists are eager to understand is how all of that information is processed at such high speeds on a continual basis.
There are three further areas of the brain that we will discuss before we close this article. The first concept is movement. There are multiple areas involved in the process of movement.
Below are the major areas that scientists have identified as critical to movement:
1. Ventral Horn:
This part is located in the spinal cord. It contains those neurons related to activating our muscles.
2. Oculomotor Nuclei:
This part is located in the midbrain. It contains neurons that active the muscles related to our eyes.
3. Cerebellum:
This is located within the hindbrain. It is the calibration system of the brain that assists with the timing of movements. Often associated with fine motor control.
4. Basal Ganglia:
Located in the forebrain, this part of the brain chooses an action based on motivation.
5. Motor Cortex:
Located in the frontal lobe, this part directs cortical activation of several of spinal motor circuits.
6. Premotor Cortex:
Also located in the frontal lobe, this area is in charge of grouping movements into coordinated and sometimes complicated patterns.
7. Supplementary Motor Area:
Located in the frontal lobe, this area controls and sequences various movements into temporal patterns.
8. Prefrontal Cortex:
Located in the frontal lobe, this area is essentially the boss of the operation. It is charged with various executive functions, including planning.
In addition to all of these areas, there is extensive circuitry meant to control the ANS, which is involved in secreting hormones and also modulates all of the gut’s muscles. In addition, the ANS affects or has input on our heart rate, salivation, perspiration, digestion, respiration and even sexual arousal. Most of these are not considered directly under our control. Yet the brain is aware of them and has accounted for them.
Pretty Incredible, isn’t it?
When it comes to behavior, the one most easily pointed to as common across species is sleeping and waking. While most of wish morning did not always come quite so early, the reality is that every creature follows some type of sleeping ritual. Bats, for instance, sleep during the day and do their insect hunting at night. This is their particular sleeping ritual. Humans are programmed to sleep when it gets dark and be active during times of light.
To be able to keep these rituals effectively, the brain must have some type of internal clock. Not only does it have this internal clock, but it is one tuned to a superfine scale, due in large part to the number of brain areas involved in this particular network. One of the key parts is the supra chiasmatic nucleus (SCN).
This is a tiny part of the hypothalamus and it is the body’s central and main biological clock. Activity levels in this clock rise and fall according to 24 hour periods, creating what is known as circadian rhythms. The rhythmic changes that occur in this area appear to be tied to what scientists refer to as the clock genes.
While you could take it out of the brain and it would still keep time, the SCN also takes in information from the eyes, so that it can calibrate itself against the light and dark we see every day. Therefore, the sunshine that we enjoy is also serving the dual purpose of helping our internal clocks to reset or realign themselves.
There are other areas that the SCN then projects to, thus resulting in the sleep/wake cycles we are so accustomed to. One important receiver is the reticular formation. Located in the lower brain, it signals the thalamus to send activity signals throughout our cortex. When this area is damaged, it can often result in a permanent coma for the brain because it simply does not know to wake up.
As we might know, sleep is a restorative state for the body. The brain directs a variety of activities while we sleep to repair and assist the body’s growth. REM sleep includes dreaming, while NREM does not usually have any dreams involved. Our brains actually switch between these patterns throughout the night. Without both, we do not get the right amount of rest necessary to function. Chemicals that are active during our daily activities drop dramatically during sleep, including serotonin and norepinephrine. Acetylcholine is the opposite and tends to rise in quantity during sleep.
Although it seems a time when brain activity would diminish, we see that it in fact is maintained. In some areas, it actually increases. Another interesting fact is that we have our own internal clock that is more accurate than many other clocks, yet it never has to be wound up or reset. Our bodies calibrate it every day when we open our eyes. Truly, it is amazing how this one small organ controls so much.
Finally, we are going to discuss homeostasis. First of all, we have to understand what that really is. The process of homeostasis is based on the idea that there are specific parameters that the body needs to have maintained in order to survive. While some variation can be tolerated, the range is typically limited.
So what are these parameters? The list includes temperature, salt concentration, water content, blood glucose and even our blood oxygen level. While there are other parameters, these are considered the biggies. The brain, of course, makes this one of the highest priorities or a critical function.
The basic idea is that any time one of these parameters shifts out of its optimal phase, a signal is sent to create a response that will return the parameter to that optimal state. This process is known as a negative feedback loop.
To see an example of this process outside of our bodies, you can look at your home’s thermostat. As long as the temperature is maintained at the range you have set, then the furnace will not turn on.
But if the temperature dips, the thermostat notes this variation and sends a signal to the furnace. The furnace then kicks on to pump heat into the home, hence providing the response that returns the parameter or temperature back to what you have determined is the optimal setting.
Our bodies function the same way. The part of the brain that plays the greatest role in maintaining our personal homeostasis is the hypothalamus. While small, it is clearly in charge of many critical functions throughout the brain and body.
There are several nuclei within the hypothalamus that receive signals from sensors located in our blood vessels. These sensors report on all the parameters, as well as giving the hypothalamus a location of the variation.
As a result, when the negative feedback kicks in, the hypothalamus turns on the output signals and attempts to address the issue or deficiency. Outputs may also go to other glands in the body, including the pituitary gland so that hormone messengers can also be sent out to create changes at the cellular level.
When we are ill, these parameters might be dramatically affected. Thus, the need to make changes at the cellular level, including sending out an increased amount of defensive white blood cells. Yet the goal of all these actions is to return our bodies to their happy place. When it cannot be achieved, the brain will send out additional signals and begin other actions meant to result in a return to homeostasis.
It was also a relatively short tour of all the functions that our brains accomplish on a daily basis. It may seem simple to close our eyes and fall asleep, but there is so much more going on behind the scenes. Our brains are changing wave patterns, sending signals to make repairs and of course, continuing its assessment of our body’s well-being.
Throughout this article, we have learned about many of the various regions and parts of the brain. Each part is not responsible for just one part or one action, but often have to demonstrate amazing multi-tasking capabilities to process all the signals that are coming in and then send out the proper output.
We have also covered a variety of individual glands that provide hormone messengers. As a result of these messengers, our bodies receive many necessary instructions from our brains. They also continue to maintain the overall parameters necessary to sustain our lives. This includes electrical fields created by the brain’s activities and the areas of the brain that control movement.
Throughout this process, we have also learned that although the brain is very complex, this also provides a protection for us as individuals. The brain is able to repair itself by transferring jobs to other areas. Essentially, a new part of the brain can relearn the task that was previously handled by the damaged area. We see this in many individuals who have strokes that cause damage to one side of the brain or the other. Yet through physical therapy and effort, our brains can make the proper adjustments.
This is just a small overview of our brains, but it should leave us in awe of how much this small organ is able to do every day. While we might sleep, our brain never shuts off. Instead it continues to work and maintain our lives. What an amazing little organ!