If the human body was compared to a machine, the brain would be the computerized system that receives input and controls what all the other parts do. In comparison to other animals, the human brain is small, yet often much more complex. Even with larger brain sizes, most animals do not have the complexity levels that the human brain does. Although the brain can be divided into multiple sections, they all function as one whole. All areas rely on the other areas to perform both complicated and simple tasks, as well as voluntary and involuntary tasks.
The average brain weighs between 2.8 and three pounds and is about 15 centimeters long. It has hundreds of wrinkles and folds on the surface, compacted into an oval shape. The brain is covered by layers of membrane called the meninges and is encased by the skull.
Although this seemingly mushy mass of folds might appear simplistic, it is quite complex. With this oval mound of tissue, there are billions of neurons, dendrites, and axons with trillions of connecting synapses. The brain also has glands and other smaller structures, divided into 3 main sections- the cerebellum, cerebrum, and brain stem.
The cerebrum is the top section of the brain, and it is divided into two hemispheres, sometimes called the left and right brains. Both the hemispheres manage the opposite side of the body, and four lobes are contained within these two hemispheres, duplicated for each hemisphere. The cerebrum has two layers called white and gray matter, denoting the inner and outer layers, respectively. The gray matter is the cerebral cortex, while the white matter is called the cerebral medulla.
It is in this section of the brain where planning and organizing, intelligence, and motor functions primarily occur. The processing and understanding of language occur here as well. Each of the four lobes has its own purpose yet work together to handle the tasks controlled by this area of the brain.
In comparison to the other three, the frontal lobe is much larger. Located at the front of the brain, this lobe is responsible for several important things. Essentially, it is where information is processed into physical movement. Although the frontal lobes of both hemispheres overlap in their functions, the right and left frontal lobes do have a few different functions.
The right frontal lobe tends to have more involvement in distinguishing specific aspects of communication, including distinguishing between negative and positive facial expressions. This lobe is also believed to distinguish certain auditory cues in speech, such as tone and emotional values in a person’s voice. Studies have also shown that the right side of the frontal lobe has more electrical activity during the expression of negative emotions. In contrast, the left frontal lobe predominantly handles language related movements, such as body language and physical emotional expression.
One thing the frontal lobe controls is motor function, and this lobe also controls speech, reasoning, and problem-solving. Emotions and memory are managed by the frontal lobe, and in addition, eye and skeletal movements, judgment, and personality are handled here as well.
Movement tasks are processed by a portion of the frontal lobe called the motor cortex. The motor cortex is divided into three areas- the primary motor cortex (M1), the premotor cortex, and the supplementary motor area. Controlling most of the movement, the primary motor cortex is responsible for the force, speed, and direction of voluntary movements. The premotor cortex determines which muscles should be used for movement, while the supplementary motor area manages the coordination of simultaneous smaller movements required to perform larger movements.
Located near the middle of the brain, the parietal lobe has the primary function of managing sensory information. Pain, taste, and touch sensations are processed in this lobe, and in addition, spatial orientation, writing, and some aspects of speech are also managed by the parietal lobe. Although most sensory information processing is spread between other lobes, the parietal lobe is the main controlling lobe.
In addition to sensory processing, the parietal lobe is responsible for visuospatial navigating and proprioception through the posterior parietal cortex. It can also help distinguish the number of objects in a visual field and coordination of attention, managed primarily by the superior parietal lobule. Known as Geschwind's territory, the inferior parietal lobule aids in processing language and facial expressions.
Located below the other lobes, the temporal lobes manage processing for sensory and auditory functions, speech related tasks, and memory storage. The temporal lobes also control facial recognition and emotional responses. Within the temporal lobes, there are a few key areas- Wernicke’s Area and the amygdala- that help with functions. The Wernicke’s Area assists in processing words and interpreting speech, and the amygdala assists in processing memories and emotions by receiving sensory information from areas in the cerebral cortex including the thalamus.
Located near the back section of the brain, the occipital lobe primary handles vision related tasks. All information relayed by the eyes is processed in this lobe, including the ability to read. The occipital lobe also works to send information about images such as the shape, size, and color and it also aids in spatial recognition tasks that include assessing the depth and distance of objects.
The lower portion of the brain is called the cerebellum, and its main duties include controlling balance and coordination. The cerebellum has a role in movement, but only in the sense of making movements more fluid. Generally, the cerebellum helps more with fine motor skills, which includes actions that require practice. It comprises about 10 percent of the brain’s weight but contains more than half of its neurons.
As with the cerebral cortex, the cerebellum also has folds that contain gray and white matter, and the folds are much more compact and smaller than others. It has three lobes that have the primary responsibility of receiving information from specific areas of the body. The anterior lobe is responsible for receiving and processing information sent by the spinal cord. Information from the cerebral cortex and brainstem are received by the posterior lobe. The flocculonodular lobe processes information sent by the vestibular nerve.
Important functions, such as heartbeat and breathing, are controlled by structures in the brain stem. Sitting just below the limbic system, the brain stem connects to the spinal cord. Ultimately, most information processed by the brain is sent to the neural pathways of the spinal cord. The pons, midbrain, and medulla oblongata are structures found in the brain stem.
Functioning with dual duty, the midbrain processes visual and auditory information, while also controlling movement. The pons is the largest section of the brain stem and joins part of the cerebral cortex to the cerebellum and medulla oblongata. It plays a large role in breathing and sleeping. Acting as the main control center for the lungs and heart, the medulla oblongata regulates blood pressure, breathing, swallowing, and heart rate.
All aspects of the brain work together through the nervous system. Each region relies on the others, working to maintain homeostasis. Neurons, dendrites, and axons run throughout the entire brain in a system of neural pathways. Information is sent through these pathways in the form of electrical impulses. There are two parts of the nervous system, each responsible for different things.
Information is received from the body and sent through a network of pathways to the appropriate processing center or lobe. The information is then sent across other areas if needed, to process the appropriate response. At this point, the response information is then sent back through the pathways to the muscles and organs required for an activity. For example, if something hot is touched, this information is sent from the nerves in the hand to the brain. The sensation is processed by the lobes that handle sensory information and then the response to jerk away from the heat is sent back to the hand to avoid more pain. All this back and forth transmission is done in a matter of seconds.
As the main control center, the central nervous system (CNS) contains the spinal cord and brain, while the peripheral nervous system (PNS) connects the CNS to the rest of the body via nerve pathways. All sensory information is received and processed in the brain and then dispersed to the appropriate neural pathways around the body. Each system is completely dependent on the other for the body to function properly.
As technology advances, medical professionals can learn more about the brain and the process behind how it works. Through imaging tests, for example, doctors can view electrical activities occurring within the brain and distinguish between damaged and healthy tissue. Understanding the brain and its complex functions allow an insight into many problems, including several psychological and processing disorders, and it can also provide an insight into the basic functioning and learning process. The human brain might be small in comparison, but it is one of the most complex organs in the body.