Brain Anatomy

What you are seeing above is a sagittal cut of the brain (also known as the encephalon if you want to be fancy :3), which means it has been divided longitudinally and cut into a left and right hemisphere. From the organism's perspective, the half above would be the right hemisphere, since when we refer to the position of a body part (for example, right atria within the heart), we always do so with respect to the organism's sense of direction. Let's dive in:

Cerebrum

The cerebrum refers to the entire mass of soft tissue (the pink, wrinkly part) that makes up the top and front part of the brain. Essentially, almost everything EXCEPT the green region (often referred to as the subcortical region of the brain) highlighted on the left! Sometimes people will call each other "smooth-brained" to insult one another (I've definitely been called that before :(( ), however interestingly enough, the tissue of the cerebrum actually appears wrinkly due to the same reason the intestinal or stomach lining does!! The space/crevices between the raised ridges are known as sulci (plural for sulcus), and the raised parts of the wrinkles are called gyri (plural for gyrus). These folds greatly increase the cerebral cortex's surface area, allowing more cerebral cortex to fit inside the limited space of the skull!  This works in the same way our intestinal lining does in order to increase surface area for absorption. The cerebrum also contains several sub parts that each serve their own functions:

• The Cerebral Cortex: The cerebral cortex consists of the outer region of the cerebrum made of gray matter, which are made up of cell bodies, dendrites and mostly unmyelinated neurons that do most of the "thinking"," logical reasoning and are responsible for more complex brain functions such as conscious thoughts, reasoning, language, voluntary movement, memory (also occurs in other parts of the brain), and processing sensory information using our five senses. Think of the cerebral cortex like the thick rind of a watermelon, where the rind represents the cortex/gray matter, and the flesh represents the deeper cerebral tissue/white matter. 

The cerebrum as we know it, is also usually thought to be split into four regions, or lobes. The frontal lobe, the temporal lobe, the parietal lobe, and the occipital lobe. Let's see what each of these do:

• Frontal Lobe (BLUE): The frontal lobe, shown in blue in the third image on the right (or below depending on what device you are using!) is responsible for complex cognitive functions such as thinking, planning, reasoning, and making decisions (of course there are a few more but those are the main ones). Within the frontal lobe are two sub-sections, known as the "Prefrontal Cortex" and the "Motor Cortex." The motor cortex facilitates voluntary movement, for example, control over the movement of one's facial features, limbs and extremities. The prefrontal cortex, like mentioned earlier, is the section of the frontal lobe that deals with the "complex cognitive functions" mentioned previously. In fact, when a person consumes alcohol, it often hinders proper function of the prefrontal cortex, which is why a drunk person may suffer from symptoms such as impaired judgement and confusion! Super cool (actually, not so much for the drunk person :(()!

• Parietal Lobe (YELLOW): The parietal lobe's job is to process sensory information received from all over our bodies (usually bodily/somatic sensations, such as touch, pressure, pain etc. Things like sight and hearing are processed in the occipital and temporal lobes respectively. We'll cover those soon!), as well as interpret it, allowing us to do numerous things. One such thing, is the ability to maintain spatial awareness and subconsciously perceive our own bodies, known as proprioception. For example, even with your eyes closed, you would have a pretty good idea of where your extremities/limbs are. You would also be able to tell the difference between your thumb and ring finger, or the difference between your ring and middle finger without actually having to look at either. Within the parietal lobe, is a region known as the somatosensory cortex, and each body part has its own "region" within the somatosensory cortex. The relative "size" of said region is based on how much sensory information comes from that body part. To the left, is the sensory homunculus!! The larger body parts represent the regions that relay the most sensory information, for example, the hands and the mouth! The ability to perceive and make sense of somatic information to perceive yourself, your surroundings, and, in turn, help make future decisions (usually where the frontal lobe takes over!) is the essence of the job of the parietal lobe!

  • • (optional read!) True story: Last year (2025), when I went to India, I was cleaning a grave that had a section that caved in near the front of it that was most likely meant for offerings. I remember minding my own business, zoning out, and cleaning the inside of it, when I suddenly felt probably one of the worst pains I've ever felt in my life. I remember pulling my hand out as fast as I could before howling at the top of my lungs and scaring the life out of everyone that was unlucky enough to be within earshot. Initially, I was too scared to look at my hand, but I already knew whatever chose to mess with me had done so on my middle finger. It ended up being a large red wasp! I ended up being OK, but my right middle finger (and part of my hand) completely swelled up. Wasps usually release certain neurotoxins that do not cause bleeding, but intense pain and sometimes swelling (like in my case!). This neurotoxin allows them to stun and kill smaller bugs and occasionally, depending on the insect, even certain rodents. Thanks to my parietal lobe, I knew exactly what finger I got stung on, how bad the pain was (definitely an 11/10 in my case), and what type of pain (for example, stinging vs. a dull, numb pain) despite being initially zoned out and too scared to look! 

• Occipital Lobe: The occipital lobe's job is to process visual signals, and things like colors, position/motion of objects, depth, distance, and primary vision in general. 

• Temporal Lobe: 

Before we dive into learning about the rest of the brain (of course, minus the cerebrum), there are many terms you will encounter on your voyage to mastering neuroscience as you reach higher and higher levels. An example, as was mentioned earlier, is the brain being referred to as an "encephalon". Similar to that, the various regions within the "encephalon" itself each have their own names! They represent specific specialized regions that each develop uniquely during birth/gestation and perform their own specialized functions as well! Here they are:

• telencephalon

• diencephalon

• mesencephalon

• metencephalon

• myelencephalon

They do sound kind of intimidating at first, but they will all make more sense soon! First, let's introduce ourselves to the forebrain (aka Prosencephalon), midbrain (aka Mesencephalon) and hindbrain (aka Rhombencephalon), as seen in the image to the right:

• Forebrain/Prosencephalon (PINK):  The forebrain consists of TWO of the five regions we saw earlier: the telencephalon, which consists of the cerebrum, cerebral cortex, basal ganglia and limbic system; and the diencephalon, which consists of the thalamus, hypothalamus and pineal gland.

• Midbrain/Mesencephalon (GREEN): The Midbrain (the midbrain also consists of certain components of its own, but for this page, we will ignore them and just focus on the components of the Forebrain and Hindbrain, referring to the Midbrain as just "Midbrain")

• Hindbrain/Rhombencephalon) (YELLOW): The hindbrain consists of another TWO of the five regions we saw earlier: The metencephalon, which includes the pons and cerebellum; and the myelencephalon, which includes the medulla oblongata (basically the upper region of the brain stem)!

Don't panic if you dont recognize certain structures yet! We will go over a majority of them in the following section: