Get to Know Your Brain!

You've heard it all before: the brain is the most complex organ in the human body. It’s the root of all thought, action, feeling, and experience of the world. While most of us are aware that the brain is central to our memories, habits, personalities, among countless other things, exactly how complex is the brain? In this article, we’ll get to know our brains, as we break down the basic neuroanatomy of the jelly-like mass of tissue sitting in our heads.

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[1] A labelled diagram of a neuron.

Consider the brain on the scale of an individual nerve cell—also known as a neuron: each seemingly minuscule structure actually has a tremendous function. The brain weighs in at around 3 pounds, and contains a mind-boggling amount of these nerve cells—around one hundred billion! These cells make up our entire nervous system, from the brain to the neurons that fire when you burn your finger on the stove. Every neuron is composed of discrete parts.

The cell body (also known as the soma) contains the nucleus and other parts of the cell necessary to sustain its life. The dendrites are root-like parts that stretch out from the cell body. These dendrites grow to make synaptic connections with other neurons. Our personal favorite component of the nerve cell, the axon, is a wire-like projection that extends from the cell body and ends at the axon terminal (otherwise known as terminal buttons). Axons typically conduct electrical impulses assay from the cell body, and into the synapse with another cell. They serve as the middle-man, transferring information into the synaptic gap for other neurons. The terminal buttons are the branched end of the axon that contain neurotransmitters. Neurotransmitters are chemicals found in terminal buttons that allow neurons to communicate. These neurotransmitters fit into receptor sites located on the dendrites of neurons. The myelin sheath is a fatty insulating layer covering around the axons of certain neurons that acts to speed up neural impulses. Schwann cells are any of the supporting cells of the peripheral nervous system responsible for the formation of myelin around the axon. Schwann cells are important because they repair and regenerate damaged nerves. Nodes of Ranvier are tiny gaps within the myelin sheath that can help accelerate the conduction of neural impulses.

The neuron is only the beginning. The amalgamation of these neurons create fascinating brain structures with various functions.

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[2] A labelled diagram of the brain’s structure.

Four predominant lobes exist in the brain: the frontal, parietal, occipital, and temporal lobes. These lobes make up the cerebral cortex. The brain can be divided down the middle (lengthwise) into two halves known as the cerebral hemispheres. Think of the cerebral cortex as eight different lobes, with four on each hemisphere. Sulci (the fissures or grooves) and gyri (the bumps) further divide each cerebral hemisphere into the four aforementioned lobes of the brain.

The frontal lobes are located at the top front part of brain behind the eyes. The anterior, or the front, of the frontal lobe is called the prefrontal cortex and is thought to play a critical role in foreseeing consequences, pursuing goals, and maintaining emotional control. It directs thought processes such as decision making or planning, and is believed to be responsible for abstract thought and emotional control. The left hemisphere of the frontal lobe typically contains a special area involved in language processing: Broca’s area. Aptly named after Paul Broca, this area controls the muscles involved in producing speech. Next time you give a presentation in front of class, thank your Broca’s area! Furthermore, the back of the frontal lobe contains a thin vertical strip called the motor cortex. This structure controls our voluntary movements by sending signals to our muscles.

Next up, we have the parietal lobes. These lobes are located behind the frontal lobe on the top of the brain. The sensory cortex (or the somato-sensory cortex) is located behind the motor cortex from the frontal lobe. The sensory cortex is also thin vertical strip, however it’s function differs from the motor cortex. Rather than controlling voluntary movements, the sensory cortex receives incoming touch sensations from the rest of the body.

Despite the occipital lobe’s location at the very back of the brain, it plays a critical role in our daily lives. This lobe interprets messages from our eyes in our visual cortex. The retinas send impulses in our eyes to the visual cortex to be interpreted by the occipital lobe. These lobes are rather ironic, considering they are the farthest away from the eyes structure-wise, yet they are key to processing visual stimuli.

The fourth and final lobe are the temporal lobes. They process the sound sensed by our ears in the form of sound waves turned into neural impulses. These neural impulses are then interpreted in our auditory cortices. A second language area is located in the temporal lobes as well. Beyond Broca’s area located in the frontal lobes, another special area called Wernicke’s area interprets both written and spoken speech. In other words, it comprehends the language that Broca’s area forms.

Thanks for reading, and join us in our next article as we discuss deep brain stimulation!

Vivian Lu