How does the brain work?
The brain works like a big computer. It processes information that it receives from the senses and body, and sends messages back to the body. But the brain can do much more than a machine can: humans think and experience emotions with their brain, and it is the root of human intelligence.
The human brain is roughly the size of two clenched fists and weighs about 1.5 kilograms. From the outside it looks a bit like a large walnut, with folds and crevices. Brain tissue is made up of about 100 billion nerve cells (neurons) and one trillion supporting cells which stabilize the tissue.
There are various sections of the brain, each with their own functions:
- the cerebrum
- the diencephalon – including the thalamus, hypothalamus and pituitary gland
- the brain stem – including the midbrain, pons and medulla
- the cerebellum
The cerebrum has a right half and a left half, known as the right and left hemispheres. The two hemispheres are connected via a thick bundle of nerve fibers called the corpus callosum. Each hemisphere is made up of six areas (lobes) that have different functions. The cerebrum controls movement and processes sensory information. Conscious and unconscious actions and feelings are produced here. It is also responsible for speech, hearing, intelligence and memory.
The functions of the two hemispheres are to a great extent different: whereas the left hemisphere is responsible for speech and abstract thinking in most people, the right hemisphere is usually responsible for spatial thinking or imagery. The right side of the brain controls the left side of the body, and the left side of the brain controls the right side of the body. This means that damage to the left hemisphere due to a stroke, for example, can lead to paralysis on the right side of the body.
The left cerebral cortex is responsible for speech and language. The right cerebral cortex supplies spatial information, such as where your foot is at the moment. The thalamus provides the cerebrum with sensory information from the skin, eyes and ears, as well as other information. The hypothalamus regulates hunger, thirst and sleep. Together with the pituitary gland, it also regulates the hormones in your body.
The brain stem relays information between the brain, the cerebellum and the spinal cord, as well as controlling eye movements and facial expressions. It also regulates vital functions like breathing, blood pressure and heartbeat.
The cerebellum coordinates movement and is responsible for balance.
Menche N. (ed.) Biologie Anatomie Physiologie. Munich: Urban & Fischer/ Elsevier; 2012.
Pschyrembel W. Klinisches Wörterbuch. Berlin: De Gruyter; 2014.
Schmidt R, Lang F, Heckmann M. Physiologie des Menschen: mit Pathophysiologie. Heidelberg: Springer; 2011.
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