Human brain: characteristics, structures and associated pathologies

For many years psychobiology has tried to establish the biological bases of human behavior.

Today we know that the nervous system of any person is a control and integration mechanism that regulates and supervises all the activities carried out by the organism. This is divided into two: the central nervous system (CNS) and the peripheral nervous system.

In turn, the CNS is divided into two more substructures: the brain and the spinal cord. Within the brain we find three substructures: cerebrum, cerebellum, and brainstem. Today we will talk about one of them. a very important structure that differentiates us from other species: the human brain.

• Related article: "Neuropsychology: what is it and what is its object of study?"

Human brain and cerebral cortex

The human brain is a complex organ made up of the cortex (lobes) and different subcortical structures (white matter and gray nuclei). The cortex would be the surface of the brain, which is divided into two: left hemisphere and right hemisphere.

An adult brain weighs approximately 1,500 grams. Although its weight represents only 2% of body weight, it consumes the same amount of energy as skeletal muscles at rest.

As for the two hemispheres that divide it, it is known that the right is more related to visual perception and a more global perception; the left would be more related to language, and would be more analytical. However, this distinction is relative, and generally, with few exceptions, both hemispheres of the human brain do everything.

The cerebral cortex is responsible for learning, thinking, and decision making., and sends signals to other parts of the brain to allow us to move and communicate. In addition, it uses the information coming from the senses and allows us to interact with the world and adapt to it.

The cortex is made up of six cell layers that allow organizing the afferents (receive information) and efferents (send information) of its neurons (approximately 60,000 million).

• You may be interested in: "Afferent pathway and efferent pathway: the types of nerve fibers"

Its organization in cerebral lobes

The human brain is made up of 5 lobes. (parts of the cerebral cortex with specific functions):

• Occipital lobe: related to vision.
• parietal lobe: related to somatoesthetic interpretation.
• temporal lobe: related to hearing and memory.
• frontal lobe: related to higher mental processes, verbal communication and voluntary motor control.
• insula: related to memory and sensory (pain) and visceral integration.

Associated injuries and pathologies

The lesion of the different cerebral lobes causes diverse pathological consequences, studied by neurology and neuropsychology. Let's see the most important ones.

Injury to the occipital lobe

visual agnosias (not recognizing objects or people by sight), Anton's Syndrome and Balint syndrome.

parietal lobe lesion

Constructive apraxias, Gerstmann syndrome, asterognosia (inability to recognize objects by touch).

injury to the temporal lobe

Hearing and comprehension impairment, Klüver-Bucy Syndrome.

frontal lobe lesion

Affectation of executive functions (dysexecutive syndrome), movement disorders, pseudodepression and pseudopsychopathy.

Ontogenetic development: divisions and structures

The human brain is divided into various structures that arise from three main divisions during gestation and the development of the nervous system.

Forebrain (forebrain, toward rostrum)

Made up of the telencephalon and the diencephalon. In turn, the telencephalon is made up of the cerebral cortex, the basal ganglia and the limbic system ("the center of emotions"); and the diencephalon is made up of the thalamus, hypothalamus, subthalamus, epithalamus, retina, and optic nerves.

midbrain (midbrain)

Formed by a subdivision with the same name, midbrain. This in turn is formed by the tectum, the tegmentum and the black substance.

rhombencephalon (hindbrain, to the back)

Made up of the metencephalon and the myelencephalon. The metencephalon is made up of the cerebellum and pons, and the myelencephalon is made up of the medulla oblongata..

Differences and similarities between humans and animals

The first difference we find between the human brain and the brain of primates, for example, is their size (larger in humans). It is known that the greater the evolutionary proximity of the species (with respect to the human being), the larger it is. Besides, the cerebral cortex of the human brain is larger and rougher than that of other animals of the same size.

On the other hand, the human brain has many more cells than those of other primates, and these also show more interconnections, that is, they have greater processing capacity.

Regarding similarities, both in animals and in humans, it is known that within the aforementioned limbic system there is a subcortical structure, the amygdala, which has been consistently linked to emotions and aggressive behavior.

In addition, recent studies reveal that in both animals and humans, aggressive behavior is frequently associated with a decrease in the activity of serotonergic neurons.

Bibliographic references:

• Netter, F. (1989). Nervous system. Anatomy and physiology. Barcelona: Salvat.
• Carlson, N.R. (2005). Behavioral physiology. Madrid: Pearson Education.
• Parra, L., García, A.A., Ortiz, S., Pérez, D., Nájera, J., Basurto, N.E., Espinoza, V. and Rivas, I. (2009). Brain anatomical differences that imply functional differences. Rev Fac Med UNAM, 52(4), 177-181.