The human brain is one of the wonders of our anatomy. What appears to be a simple organ is, in fact, an incredibly complex structure with multiple parts that work both with each other and with information received from the rest of the body. Healthy brain function is essential for thought, reasoning, memory, speech, movement, and life itself.

The Three Parts of the Brain

Since the parts of the brain all work together to help humans grow, learn, and process their experiences, it is difficult for those without in-depth knowledge of neuroscience to ascertain what part of the brain is responsible for which actions. Though they still don't know everything, scientists agree the brain has three main parts. The cerebrum is the largest and is divided into right and left hemispheres; the cerebellum is located under the cerebrum and helps control balance and movement; the brainstem connects the rest of the brain to the spinal cord and regulates essential survival-related functions.

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Functions of the Left and Right Hemispheres

When people picture the human brain, the cerebrum is probably what most envision. The large mass splits into the right and left hemispheres that are joined by the corpus callosum, a bundle of nerve fibers that can transmit neural messages between the two halves. The right hemisphere controls the left side of the body, and the left hemisphere controls the right side of the body. Though there can be some overlap, each hemisphere does different things. In general, the left hemisphere is responsible for understanding and using language when we listen, speak, read, or write. The right hemisphere provides spatial awareness of surroundings and our physical positions within space. Both hemispheres play critical roles in different types of memory. The neuron-dense surface of the cerebrum is called the cortex.

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The Lobes of the Hemispheres

Each cerebral hemisphere has four lobes: frontal, temporal, parietal, and occipital. Each lobe can be further divided into specialized areas researchers believe are critical for performing particular functions. The frontal lobe is the main center for personality, judgment, and emotions. Scientists believe the areas responsible for self-awareness and intelligence also reside in the frontal lobe. In the left hemisphere, the frontal lobe is where you will find Broca's area, a collection of neurons responsible for the production of speech. Damage to this area can make communication difficult.

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The Temporal Lobe: Memory

Moving to the side of each hemisphere of the cerebrum, we come next to the temporal lobe, the site of the neurons that control hearing and memory acquisition. This is the location of a specialized region, Wernicke's area. Damage to this region can result in problems with understanding speech. The temporal lobe also contains parts of the brain vital to understanding visual input, such as recognizing faces and categorizing objects.

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The Parietal Lobe: Sensory

The parietal lobe sits in the upper back of the cerebrum. This is where the brain processes information received from sensory inputs such as taste, touch, pain, and temperature. The integration of this sensory data is what helps a person understand a concept. Because it is so important for interpreting sensory data, the parietal lobe is also important for navigating spatial relationships and manipulating objects.

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The Occipital Lobe: Vision

The occipital lobe is at the very back and bottom of the cerebrum and is responsible for processing visual sensory information from the eyes. Though the eye takes in visual data, the image is only fully processed and interpreted in the brain. Signals from the eye travel along the optic nerve, ending up in the occipital lobe where the brain forms an understanding of what the eye is seeing. Damage to this area can lead to visual problems including difficulty recognizing colors, identifying objects, and reading and writing.

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The Cerebellum: Movement and Balance

Smaller than the cerebrum, the cerebellum is nonetheless an important part of the brain when it comes to movement, balance, and maintaining posture. The cerebellum receives sensory information and uses it to regulate motor movements. A healthy cerebellum produces smooth and balanced voluntary muscular activity and helps us learn new motor skills. In addition to other types of memories, the cerebellum processes skill memories, which are learned actions that have become almost automatic. Examples include tying a shoe, playing a musical instrument, and riding a bicycle.

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The Brainstem: Critical Functions

Like an important intersection in a big city, the brainstem is a critical region; all information to and from the body must pass through it. In humans, the brainstem is divided into three parts: the medulla oblongata, the pons, and the midbrain. These three parts work together to control some of the most basic functions of the human body including breathing, heart rate, blood pressure, reflexes, and swallowing. In addition, the brainstem maintains consciousness. Because the brainstem controls functions essential for life, injuries to this area can be particularly devastating.

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The Pineal and Pituitary Glands

In addition to being the center of the human nervous system, the brain is also an important player in the endocrine system since it is the home of the pineal and pituitary glands. The pineal gland produces melatonin, the sleep-inducing hormone derived from the amino acid tryptophan that helps organisms regulate their circadian rhythms. The pituitary gland is often called the "master gland" because it regulates other important glands in the endocrine system including the adrenal, thyroid, and reproductive glands. The pituitary gland also secretes hormones important for bone and muscle growth.

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The Hypothalamus: Linking the Nervous and Endocrine Systems

The hypothalamus is one of the "deep structures" of the brain. This almond-sized part sits near the base of the brain and communicates with both the brainstem and the cortex. Though it is small, the hypothalamus is the master of the autonomic nervous system, coordinating several critical functions including body temperature, thirst, hunger, sleep, and emotional responses. Through the secretion of neurohormones and neurotransmitters, it also controls the activity of the pituitary gland, linking the nervous system and the endocrine system.

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