Understanding Brain Anatomy: A Detailed Look at the Parts of the Brain and Their Functions
It’s impossible to overstate the importance of our brain. The organ, housed inside the skull and protected by a bony covering called the cranium, controls thought, memory, emotion, vision, and motor skills. It’s also responsible for every process that regulates our body, including breathing, temperature, and hunger.
But don’t let the brain’s complexity intimidate you. An understanding of the basics about the brain’s structure and function can be empowering, and even help people with a brain condition help their care team monitor symptoms, says Jordan Komisarow, MD, an assistant professor in the departments of neurosurgery and neurology at Duke University School of Medicine in Durham, North Carolina.
Keep reading to learn about the anatomy of the brain.
“To better understand the anatomy of the brain, it can be subdivided into three parts: the cerebrum, cerebellum, and the brainstem, with the basal ganglia and diencephalon as connecting stations between these,” Dr. Komisarow says.
The largest (and perhaps the most famous) part of the brain is the cerebrum, says Komisarow. The cerebrum makes up about 80 percent of the brain.
“When most people think of ‘the brain’ they are thinking of the wrinkles of gray and white matter of the cerebrum,” he says.
Located in the front of the brain, the cerebrum is covered with gray matter, called the cerebral cortex, with white matter at the center.
The cerebrum is where thinking is done, and also where we start actions, like speaking to our friends or processing what our senses take in, says Komisarow.
For most people, the left brain hemisphere is dominant; most people who are right-handed are left hemisphere dominant. And most people who are left-handed are right hemisphere dominant.
“It is largely involved in balance and coordinated movement,” says Komisarow.
“It contains a lot of important centers that control bodily functions that occur automatically, like breathing,” Komisarow says.
Respiration, heart rate, wake-sleep cycles, coughing, sneezing, digesting food, and vomiting are all housed in the brainstem.
The brainstem also plays a role in some functions we do control, such as eye movements and swallowing, says Komisarow.
The diencephalon is the term for a group of brain centers located in the middle of the brain at the core of the cerebrum, says Komisarow.
“It serves as a sort of relay station for information from your senses and for planned movements, and it plays an important role in being awake and alert,” Komisarow says.
There are four lobes in the cortex of the cerebrum: the frontal lobes, parietal lobes, temporal lobes, and occipital lobes.
“The frontal lobes are aptly named for being in the front of your head,” says Komisarow.
“A part of the cerebrum, the part of the frontal lobes called the primary motor cortex or precentral gyrus helps with planning and execution of voluntary movement,” he says.
The parietal lobes are located behind the frontal lobes near the center of your brain.
“These lobes help with how a person senses things throughout their body and helps your brain make sense of what’s going on around you,” says Komisarow.
They contain the primary somatosensory cortex, which processes sensory input, including touch, pain, temperature, position of the body, and location in space.
The temporal lobes are located near your ears at the bottom of your head on each side of the brain.
There are structures deep within the brain that serve as “gatekeepers” between the spinal cord and the cerebral hemispheres.
The limbic system of the brain is a group of structures that control emotions, behavior, instinct, and motivation.
The basal ganglia are a group of paired brain centers that largely deal with controlling movement located in the center of your brain.
The parts of the basal ganglia include:
These separate structures link up in various, complex ways and send signals back and forth to one another.
“Together, these form an important network in getting a movement planned in another part of the brain correct,” Komisarow.
Other jobs of the basal ganglia include processing how you evaluate goals, risks, and rewards; it also plays a role in learning and forming habits, and in forming and executing a plan.
“The corpus callosum is the group of cells deep within the middle of the brain that serve as the wiring that connects the left and right side of the brain,” says Komisarow.
The brain and spinal cord are surrounded and protected by three layers of protective covering called meninges.
The blood-brain barrier and cerebrospinal fluid provide additional modes of protection for the brain.
“The meninges are the cloth-like covering of the brain that are normally composed of three layers. Outside to inside, these are the dura, arachnoid, and the pia,” says Komisarow.
Dura mater is thick and tough. It includes two layers, the periosteal layer that lines the inner dome of the skull (cranium) and the meningeal layer is below that. Spaces between the layers contain veins and arteries that supply blood flow to the brain.
Arachnoid mater is a thin, weblike layer of connective tissue that doesn’t contain nerves or blood vessels.
The blood-brain barrier is like a gatekeeper for your brain. Tightly packed endothelial cells lining the inside of the brain’s blood vessels work as a filter to keep harmful things out and hold helpful things in.
Some things are small enough to get through the BBB, and other things can pass through because they’re lipid-soluble and are therefore not repelled by the lipid-based outer membrane of the endothelial cells.
“Cerebrospinal fluid, or CSF, is found below the arachnoid mater. The clear fluid cushions the entire central nervous system (brain and spinal cord) and continually circulates around these structures to remove impurities,” says Komisarow.
CSF can be sampled and analyzed via a lumbar puncture (also known as a spinal tap) to look for certain diseases. Intracranial pressure can also be measured during a lumbar puncture.
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