Brain

The brain is a complex organ that manages many of our bodily functions, such as balance or breathing. It also controls our memories, emotions, and thoughts. The brain is the physical structure which gives rise to the abstract concept we call the mind.

Any damage or malfunction in the brain can have a serious impact on our wellbeing. Some mental health issues, such as schizophrenia, are thought to originate in the brain.

However, therapy and medication can change brain function and help relieve symptoms for many mental health conditions.

Brain cells

To understand the brain, it helps to start with its most basic components: cells. There are two types of cells in the brain: neurons and glial cells.

Neurons

The average adult has billions of neurons in their brain. Neurons (also called nerve cells) transmit messages through a combination of electrical and chemical signals.

In general, neurons communicate like so:

• An electrical signal prompts a neuron to release a sac full of chemicals called neurotransmitters.
• These neurotransmitters travel out of the first neuron to another neuron across a gap called the synapse.
• Certain neurotransmitters will either raise or lower the electrical charge in the second neuron.
• If the second neuron gets its electrical charge high enough, it will release its own neurotransmitters, passing the chemical “message” on to other cells.

Scientists can examine brain activity by measuring the electrical charge of neurons.

Glial Cells

Brains also have a second type of cell called a glial cell. These cells perform support functions such as:

• Regulating the blood-brain barrier so that nutrients can come into the brain but bacteria can’t.
• Secreting cerebrospinal fluid.
• Creating a fatty sheathe around nerve cells to speed up electrical messages.
• Synaptic pruning: Getting rid of unused connections between neurons so the brain can prioritize its resources on more important functions.

Glial cells are around 50 times more common than nerve cells. As such, most brain tumors are made of glial cells.

Regions of the Brain

Most scientists divide the brain into three main parts: the brain stem, the cerebellum, and the cerebrum.

• The brain stem resembles a flower stem connecting the spinal cord to the rest of the brain. It acts as a relay center between the brain and the rest of the body. It controls many unconscious functions necessary for survival, such as breathing and digestion.
• The cerebellum is located at the back of the head, sandwiched between the brain stem and the cerebrum. It manages our sense of balance and our fine motor movements (such as typing).
• The cerebrum is the largest portion of the brain, and it’s the part most often shown in pictures. It allows us to do complicated functions such as form memories, feel emotions, translate thoughts into words, and so on.

The brain can also be divided into the left and right halves, also called hemispheres. These hemispheres are connected by a bundle of nerve fibers in the middle called the corpus callosum. The corpus callosum allows the hemispheres to communicate with each other.

In general, each brain hemisphere controls the functions that occur on the opposite side of the body. For example, damage to the left hemisphere may affect one’s ability to see out of their right eye. Sometimes, when a portion of the brain is damaged, its function can be outsourced to the other hemisphere.

The Cerebral Cortex

The wrinkled surface of the cerebrum is called the cortex. This is where almost all the neuron synapses are, so it is where communication between neurons takes place. The cortex’s lumps and folds increase its surface area, allowing more room for neurons to communicate.

Under the cortex, the neurons have long, spindly fibers called axons, connecting both ends of the cell. The axon is similar to an old-fashioned telephone line, transmitting signals from one part of the cell to another. The receiving end of a neuron may be at a completely different area of the cortex than the end that sends out neurotransmitters.

The axons are covered in a whitish fatty sheathe, so the tissue under the cortex is often called “white matter”. The parts of the nerve cells in the cortex are gray, hence why the cortex is sometimes called “gray matter”.

Lobes of the brain

The cerebrum can be divided into specialized sections of the brain called lobes.

• Occipital lobe: It processes visual information, such as colors and shapes. It receives messages from our eyeballs and translates them into a cohesive picture from two separate eyes.
• Parietal lobe: This lobe processes sensory data from touch, pain, sound, and so on. It also helps us interpret language.
• Temporal lobe: This section is heavily involved in visual and verbal memory. It also helps us interpret others’ emotions.
• Frontal lobe: The very front of this section is called the prefrontal cortex, and it controls our emotions, personality development, and ability to make decisions. This lobe also gives us the ability to move and speak.

These lobes often work together to perform everyday functions. For example, the task of reading out loud may require the occipital lobe to see the letters, the temporal and parietal lobes to make meaning of the words, and the frontal lobe to physically speak.

Protecting the Brain

The brain sits inside the bony skull that helps protect it from falls, blows, and other injuries. However, the brain isn’t bouncing in the skull by itself. The skull cavity also contains a clear liquid called cerebrospinal fluid (CSF), which further cushions the brain.

CSF is created within hollow cavities in the brain called ventricles. The fluid flows between these cavities, then out and around the brain, filling the small gap between the brain and skull. Typically CSF is absorbed as quickly as it is produced, so fluid levels are often stable. If there is a disruption in the system, the fluid can build up, putting pressure on the brain and causing tissue damage.

References:
1. Action potentials and synapses. (n.d.). The University of Queensland. Retrieved from https://qbi.uq.edu.au/brain-basics/brain/brain-physiology/action-potentials-and-synapses
2. Anatomy of the brain. (n.d.). American Association of Neurological Surgeons. Retrieved from https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Anatomy-of-the-Brain
3. Anatomy of the brain. (2018). Retrieved from https://mayfieldclinic.com/pe-anatbrain.htm
4. Audesirk, T., Audesirk, G., & Byers, B. E. (2008). Biology: Life on earth with physiology. Upper Saddle River, NJ: Pearson Prentice Hall.
5. Grey matter and white matter. (n.d.). Retrieved from http://www.indiana.edu/~p1013447/dictionary/greywhit.htm

Last Updated: 07-25-2019