Human brain

The human brain is the central organ of the nervous system. Together with the spinal cord, it forms the central nervous system. The brain acts as a control center for the entire body. It processes, integrates, and coordinates information from the sensory nervous system. This allows the body to react to the world around it. The brain is a very soft organ. It has a gel-like consistency similar to soft tofu.

The brain is divided into three main structural parts. These are the cerebrum, the brainstem, and the cerebellum. The cerebrum is the largest part and sits on top. It consists of two cerebral hemispheres. These hemispheres are separated by a deep groove called the longitudinal fissure. They are connected by nerve tracts called commissures. The largest of these connections is the corpus callosum.

Each hemisphere of the cerebrum has a specific structure. The outer surface is the cerebral cortex, which is made of grey matter. This cortex contains layers of neurons. The largest part of the cortex is the neocortex, which has six neuronal layers. The inner part is called the allocortex, which has three or four layers. Beneath this grey matter lies the white matter. This white matter is made of myelinated axons. It makes up about half of the total brain volume.

The cerebral cortex is organized into specialized lobes. The frontal lobe handles executive functions like reasoning and planning. The occipital lobe is the smallest and is dedicated to vision. The temporal lobe manages auditory and visual memories, language, and speech. The parietal lobe is involved in sensory processing. Some sources also include a central lobe, a limbic lobe, and an insular lobe. These areas work together through complex association areas to handle thought and decision-making.

Deep inside the brain, several important structures regulate body functions. The brainstem connects the cerebrum to the spinal cord. It includes the midbrain, the pons, and the medulla oblongata. Behind the brainstem sits the cerebellum. The cerebellum is divided into an anterior lobe, a posterior lobe, and a flocculonodular lobe. Deep within the hemispheres, the basal ganglia help regulate movement and behavior. These include the striatum, the globus pallidus, and the substantia nigra.

Brain activity relies on a massive network of cells. There are more than 86 billion neurons in the brain. There is also a roughly equal number of supportive glial cells. Neurons communicate through a process called neurotransmission. They release chemicals known as neurotransmitters in response to nerve impulses. These cells connect to form neural pathways and elaborate circuits. The brain is protected by the skull and cushioned by cerebrospinal fluid. This fluid circulates through a system of four interconnected ventricles.

Scientists use different fields to study these complex systems. Neuroanatomy is the study of the brain's physical structure. Neuroscience is the study of how the brain functions. Researchers use medical imaging and electroencephalography (EEG) to observe activity. They also learn from the medical history of people with brain injuries. The brain is susceptible to many issues. These include strokes, which are a loss of blood supply. It can also face degenerative disorders like Alzheimer's disease or Parkinson's disease.

Humanity has long been fascinated by the nature of the mind. For centuries, philosophers have explored the mind-body problem. In the 19th century, a pseudoscience called phrenology attempted to map personality to the skull. This idea was incorrect, but it shows our early desire to understand the brain. Today, we continue to explore the brain through advanced technology. We even see the brain's importance in science fiction, such as stories about brain transplants.