The human brain is unique in its anatomy. The brain consists of billions of nerve cells that are interconnected in complex ways. Nevertheless, the brain can be easily divided into different components and areas, some of which have specific functions. This article provides you with an overview of the anatomy of the human brain.
Rough division of the brain into 5 parts
The human brain anatomy can be described in various ways. Initially, it makes sense to consider the brain (encephalon) divided into five main regions. These five areas of the brain are recognizable to varying degrees in all vertebrates:
- Cerebrum, often also called telencephalon
- Diencephalon (interbrain)
- Midbrain (mesencephalon)
- Hindbrain (metencephalon)
- Myelencephalon (also: medulla oblongata)
The designation of these main regions is based on the simple brain anatomy of lower vertebrates, in which the regions lie one behind the other in a tubular shape. The human brain, in comparison, is more complex, but these five brain parts are still clearly recognizable despite further evolutionary development. To give you an idea of the human brain, we will take a closer look at the five brain regions mentioned and describe further classification options within brain anatomy.
The cerebrum and diencephalon form the forebrain (prosencephalon)
The forebrain consists of the cerebrum and the diencephalon. The large cortex of the cerebrum (cerebral cortex, cortex cerebri) is particularly characteristic of human brain anatomy. Its characteristic convolutions (gyri) and furrows (sulci) cause a significantly enlarged surface area, which allows the volume to remain relatively small.
The cerebrum is composed of two hemispheres, which are separated by the fissure "fissura longitudinalis cerebri". Deeper inside, however, they are connected by the so-called corpus callosum. In a frontal section of the brain, the gray and white matter of the hemispheres are visible.
The image "Brain structure in cross-section" depicts the brain anatomy in such a section.
The outer gray matter consists mainly of the cell bodies of the nerve cells and the inner white matter of the nerve fibers.
The 4 Cerebral Lobes of the Cerebrum
Both hemispheres can be divided into four lobes based on certain sulci:
- Frontal Lobe (Lobus frontalis)
- Parietal Lobe (Lobus parietalis)
- Occipital Lobe (Lobus occipitalis)
- Temporal Lobe (Lobus temporalis)
As the name suggests, the frontal lobe is located at the front in the forehead area. The parietal lobe borders the frontal lobe from behind and extends to the occipital lobe located at the back of the head. The temporal lobe is located laterally below the parietal lobe. The location of the cerebral lobes corresponds to the similarly named cranial bones, as shown in the image "Cranial Bones Anatomy".
Functional Areas of the Cortex
The human cerebral cortex is particularly highly developed. It is responsible for characteristics
that make humans what they are. Certain functions can be assigned to some areas of the cortex. For example, the temporal lobe contains areas that process auditory information. The occipital lobe contains the primary visual cortex, which handles part of the visual information processing.
The parietal lobe contains areas of somatosensory perception, which convey information from the skin, organs, muscles, and joints. The motor speech center and other motor areas are located in the frontal lobe. Areas involved in personality development are also found there.
The Structure of the Diencephalon
Located between the hemispheres of the cerebrum is the diencephalon with the following structures:
- Thalamus
- Epithalamus with Epiphysis
- Hypothalamus with Neurohypophysis
- Subthalamus
The thalamus serves as a control center through which almost all information flowing to the cortex passes. It is also known as the "gateway to consciousness." You can see the location of the thalamus in the image "Brain - Sagittal Section." This shows the brain anatomy in a sagittal section, i.e.,
in the lateral view. The epithalamus, situated on the thalamus, houses the pineal gland (epiphysis). This produces melatonin, known as the sleep hormone, and is thus involved in the sleep-wake cycle.
The hypothalamus lies below the thalamus and is connected to the pituitary gland (hypophysis). The pituitary gland, which is partly responsible for hormonal control, is divided into the posterior lobe (neurohypophysis) and the anterior lobe (adenohypophysis). The adenohypophysis, which is made up of glandular cells, is not part of the brain. The hypothalamus controls, among other things, the autonomic nervous system, but is also involved in emotional life.
The limbic system consists of structures of the forebrain
The limbic system represents another functional division within the brain anatomy.
It comprises brain structures responsible for the control of emotions. In addition, the limbic system plays important roles in learning and is in contact with the hypothalamus. It surrounds the corpus callosum, which connects the two hemispheres. The limbic system includes:
- Structures of the olfactory bulb
- Amygdala
- Hippocampus
- Cingulate gyrus
- Parahippocampal gyrus
Due to the close relationship between the olfactory bulb and the other structures of the limbic system, smells, memories, and emotions are often linked. The amygdala plays an essential role in the development of fear, while the hippocampus is important for learning processes and is involved in aggression and motivational behavior.
The Anatomy of the Brainstem and Cerebellum
The midbrain, the pons of the hindbrain, and the medulla oblongata form the brainstem (truncus cerebri). The nuclei of the cranial nerves, fiber bundles of the hypothalamus, and long nerve cell pathways are located there.
All three parts of the brainstem are connected to the cerebellum, which rests on the brainstem. The cerebellum consists of the vermis (vermis cerebelli) and two hemispheres (hemispheria cerebelli). Together with the pons, it forms the hindbrain and is responsible for balance, muscle tone, and the coordination of muscle activity.
With the medulla oblongata, the brainstem finally merges into the spinal cord, whereby the gray and white matter rearrange. From a developmental perspective, the brainstem is the oldest part of human brain anatomy.