The Basics of Brains

by Charlie Snow
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​The Basics of Brains Still one of the least understood organs in the human body, brains have long confused neuroscientists who long to discover the inner workings of the mind in general and in relation to abstract concepts like consciousness and thought. Arguably the thing that makes humans human, the brain is like the world’s most intricate, complicated, and sensitive computer… and also about 10 million times slower than your average desktop. While there is still much that is unknown to the world about how exactly brains work, there is also a lot that is known about the human mind.

So let’s begin with the basics. Starting with the outside of the mind, your brain is protected from the uneven surface of the inside of your skull by protective layers called meninges. Dura mater, the outermost layer, is a vascular (meaning it has blood vessels) layer that lines the inside of the skull with a second meningeal layer below that helps with blood flow to the brain. The middle layer, called arachnoid mater, is a thin weblike nonvascular layer of connective tissue that surrounds the brain, keeping cerebrospinal fluid in place that cushions the central nervous system and removes impurities. The third and innermost layer, pia mater, hugs the surface of the brain and is rich with veins and blood vessels that supply the brain with oxygen. The brain itself is about three pounds and made up of a thin outer layer of gray matter (mostly composed of neurons) and a dense inner layer of white matter (mostly composed of axons).

Now that we’ve gotten through what protects your brain, let's go to the main parts of the brain, the cerebrum, cerebellum, and brainstem. By far the largest of the three, the cerebrum takes up 85% of the brain and controls almost everything you do. It initiates and coordinates movement, regulates temperature, enables speech, judgment, thinking, reasoning, problem solving, emotions, learning, and the five senses. The outer layer of the cerebrum, the cerebral cortex, houses many of the parts of the brain that set humans so much higher than other animals in terms of intelligence, such as the prefrontal cortex, a newly evolved portion of the brain that only exists at a similar level to humans in primates (though the human prefrontal cortex is much more evolved). Split into a left and right half, the cerebrum’s right hemisphere controls the left side of the body while the cerebrum’s left hemisphere controls the right side of the body. These halves communicate through a large C-shaped structure made of white matter and nerve pathways found in the middle of the cerebrum called the corpus callosum.

The cerebellum, affectionately known as the little brain, is a fist sized portion of the brain located in the back or your head and above your brainstem. Much like its much larger sibling, the cerebellum is split into two hemispheres where right controls left and left controls right. The outer portion of the cerebellum, coated in gray matter, and the inner portion work hand in hand to coordinate purposeful muscle movements and maintain posture, balance, and equilibrium. Think of it as a tool that fine tunes smaller movements like typing with your fingers or how exactly you kick a soccer ball, making sure they’re just to your liking.

The last portion of the brain, the brainstem, is located at the bottom of your brain, between the cerebrum and the cerebellum, and connects them to the spinal cord. The top of the brainstem, called the midbrain, is a complex structure with a range of different neuron clusters that helps with things like hearing and movement and also aids in bodily responses to environmental change. Below the midbrain lies the pons, a small horseshoe shaped mass of nerves that connects to the midbrain and the cerebellum. The pons not only houses four of the twelve cranial nerves that help supply blood flow to the brain, it also helps with tear production, chewing, blinking, focusing vision, balance, hearing, and facial expressions- and it also acts as a bridge between the midbrain and the final portion of the brainstem, the medulla. Located at the bottom of the brainstem, the medulla connects the brain to the spinal cord and is essential for survival. It regulates reflexive activities such as sneezing and vomiting and involuntary bodily functions like heart rhythm, breathing, blood flow, and even your oxygen and CO2 levels.

The final part of our brain basics will be a quick overview of the four main lobes that make up the cerebrum. The largest and frontmost lobe of the brain, the frontal lobe is the most highly developed and is mainly involved in creating your personality characteristics, decision making, and movement. Other skills like recognition and smell also involve the frontal lobe. The parietal lobe, located in the middle of the brain, is only slightly smaller than the frontal lobe. The parietal lobe helps more with individual object identification, spatial relationships (interpreting the relationship between your body and the objects around it), and understanding pain and touch in relation to your body. The occipital lobe, located at the back of the brain above the cerebellum, is much smaller than the other two lobes and is responsible for your visual perception of things such as color, shape, and movement. The fourth and final lobe, the temporal lobe, can be found on the left and right sides of the brain and helps with short term memory, speaking, musical rhythm, and some degree of recognition.

Again, these are only the basics of brain biology. There are hundreds of structures, cortices, glands, and systems that help the brain function the way it does. Let us know if you’d like to learn more!

Sources:
https://www.hopkinsmedicine.org/health/conditions-and-diseases/anatomy-of-the-brain