Have you ever pondered on how human organs coordinate and control the processes of life? All these coordination are organized by one and only master organ, which is the brain. The brain is a three pounds complex organ responsible for controlling our emotions, thoughts, and bodily processes. The brain comprises 86 billion brain cells, also referred to as neurons. Neurons enable data or signal communication across all body organs, hence are the key brain components.

Brain structure

The brain anatomy includes four major parts: the cerebrum, cerebellum, brainstem, and diencephalon (Figure 1).

Figure 1 The Brain Anatomy.


It is the largest area of the brain capable of higher-level functions like thinking, reasoning, memory, and voluntary movement.

The cerebrum has two major parts; cerebral hemispheres and cortex.

Cerebral hemispheres

The left and right cerebral hemispheres are interconnected through a bridge of nerve fibers called the corpus callosum. Each hemisphere controls the functions of the opposite side of the body; for example, right side of the body is under control of the left hemisphere and vice versa.

Cerebral cortex

The cerebral cortex comprising layers of cell bodies and dendrites lies on top of the cerebrum, also called the gray matter, responsible for enhanced neural connections. The cerebral cortex is mainly involved in consciousness. Over time, the brain accumulates additional information, causing corticalization of the cortex, making it a highly wrinkled structure. Therefore, the wrinkle your brain, the smarter and more intelligent you are.

Cerebral hemispheres are divided into four lobes (Figure 2):

  • Frontal lobe
  • Parietal lobe
  • Temporal lobe
  • Occipital lobe
Figure 2 Four Lobes of the Brain.

Each lobe performs a specific function and contributes to overall cognitive abilities.

Frontal lobe

It is present behind the forehead and just in front of cerebrum. It involves critical functions like taking judgements, resolving problems, being attentive, commanding emotions and behaviors, vocalization, personality, intellect, and motion.

Occipital Lobe

It is located behind the brain and is accountable for illustration of visual data received from the eyes regarding color, motion and orientation. It also involves object and facial recognition, depth and distance perception.

Parietal Lobe

It is situated in between frontal and occipital lobes and just above temporal lobe. Sensations like touch, warmth, and pain are processed here. It also provides the ability of spatial processing through which an individual can navigate his location in three-dimensional space.   

Temporal Lobe

It is situated below the parietal lobe and plays a significant role in auditory processing, language comprehension, memory formation, recognizing faces and interpreting emotions.

The cerebellum

Cerebellum holds 10% of the brain’s volume. It is 4.5 inches wide and located under the cerebrum, lower to occipital and temporal lobes, at the back side of the brain. Tentorium cerebelli are the connective tissue layers separating the cerebellum from these lobes.

The cerebellum comprises around 80% of neurons and serves a vital function in regulating voluntary movements, maintaining bodily balance, and maintaining posture. Cerebellar sensors detect alterations in balance and coordination. It transmits messages to the body to modify, move, maintain stability, and make the appropriate modifications to maintain upright posture. It also organizes the actions of different muscle groups so that the body can move freely. Cerebellum also provides the capacity for motor learning like learning to ride a bicycle or play an instrument, which requires repetition and refinement. Additionally, the cerebellum regulates eye movement.

The third part of the brain is called the brainstem.


Brain and spinal cord are interconnected through brainstem, a stalk-like part present below the brain. It regulates actions, including breathing, pulse rate, blood pressure, face sensations, swallowing and gastrointestinal functions. The brainstem has ten cranial nerves that control facial movements, sensations and taste.

Brainstem consists of three parts that work together in a harmonious way to authorize involuntary actions to keep our body working:

  • Midbrain
  • Pons
  • Medulla oblongata.

Let’s explain each component one by one.


It is the topmost part of the brainstem. The midbrain commands motor movement, specifically eye movements and perception of sound and sight. It facilitates communication among various brain regions by acting as a relay station for sensory and motor signals. It also maintains the sleep and wake-up cycles.


The middle and largest portion of the brainstem lies between the medulla oblongata and cerebellum. The pons is a nerve fiber bridge that connects the medulla to the cerebellum. The pons influences the sleep cycle, relaying and regulating the signals that give pain sensations. It also coordinates with other parts of the brainstem, which regulate breathing, facial expressions and rapid eye movement (REM) sleep, the phase in the sleep cycle in which a person experiences dreams.

Medulla Oblongata

It is the terminal part which connects the brainstem with the spinal cord. It controls and commands life sustaining functions of the body like pulse rate, blood pressure, breathing and digestion.

Regulation of Autonomic Functions

Homeostasis is maintained and regulated by the brainstem by receiving and sending signals from several sensory receptors to ensure the body runs properly.

Integration with Higher Brain Regions

Although the brainstem is primarily associated with basic functions but interacts with higher brain regions, it receives input from the cerebral cortex, allowing for voluntary control over certain functions like breathing rate and heart rate modulation.


The last part of the brain is called Diencephalon: This region includes the thalamus and hypothalamus. 


The egg-shaped thalamus, located at the top of the brainstem, is a relay station for sensory information. It receives impulses in the form of nerve signals from various sensory organs and sends it to the brain for further processing.


Moving on to the hypothalamus, situated just below the thalamus, its function is to keep the body in a stable state called homeostasis. It manages temperature fluctuations in the blood and initiates responses to regulate body temperature accordingly, such as shivering or sweating. The hypothalamus also plays a role in regulating our feelings of hunger and thirst. In response to these signals, it initiates behaviors to obtain food and water, ensuring our nutritional and hydration needs are met. The hypothalamus interacts with the pituitary gland to release hormones that further influence other endocrine glands to regulate processes such as growth, metabolism and reproduction; thus, it also plays a crucial role in managing the endocrine system.

 Neurons or nerve cells are the fundamental blocks of the nervous system. These are the key components that control brain activities. A neuron has three major parts, including the cell body, dendrites, and an axon. A synapse is a small gap at the end of each neuron, and it allows signal transfer between two neurons. An electrical impulse induces neurotransmitter release when it reaches the end of one neuron’s axon, which carries the signal to the next neuron.

Unfortunately, the brain is vulnerable to a wide range of disorders. Diseases such as Alzheimer’s, Parkinson’s, epilepsy, and stroke can all cause permanent damage to brain tissue and function.(Figure 3), resulting in cognitive and movement defects.

Figure 3 Brain illnesses

The human brain is the most diverse and versatile element of the body. The brain’s many responsibilities include acting as the body’s control center, translating what we experience, sparking action, and directing behaviour. Everything that makes us human has its origins in the brain.

About the author

Dr. Madilyn Adams is a PhD in molecular medicine from Harvard University and has been working as a medical blogger for seven years.


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