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The structure of the midbrain is revealed: Why is it called the "center of the brain"?
The midbrain is the uppermost part of the brainstem, responsible for connecting the diencephalon and the brain, and is in charge of a variety of important life activities. Although this structure located in the posterior cranial fossa is less than 2 centimeters long, it plays an important role in various basic functions of the body. The main functions of the midbrain include vision, hearing, motor control, sleep and wakefulness, alertness, and temperature regulation.
The name mesencephalon comes from the Greek words "mesos", meaning "middle", and "enkephalos", meaning "brain".
Structural analysis
Due to its short structure, the midbrain is further divided into several important regions, including the upper cover, cerebral aqueduct, base, and cerebral peduncles. Anatomically, it exhibits pronounced lateral bulging above and below, which gives the midbrain a shape similar to an inverted bear's face, especially when severed above or laterally.
Tectum
The upper lid is located on the dorsal side of the cerebral aqueduct and is the top of the midbrain. Due to its position, the top cover also forms a clear distinction from the base at the front. The superior operculum is involved in certain reflexes in response to visual and auditory stimuli and is connected to the rest of the body through different neural pathways.
The four bulges on the upper cover, called the four clusters, are divided into upper and lower pairs and are responsible for different audio-visual information processing.
Cerebral Aqueduct
The cerebral aqueduct is the channel that connects the third ventricle and the fourth ventricle, and is also an important channel for cerebrospinal fluid circulation. This narrow channel, located between the upper lid and the base, is surrounded by perineal aqueous matter and is associated with certain neural activity.
Bottom (Tegmenum)
The base of the midbrain is the larger portion located in front of the cerebral aqueduct and contains a rich network of neurons primarily involved in life support and reflex reactions. The base also contains some important nerve tracts, including the medial fasciculus and the ascending spinal process, structures that are crucial in the functioning of the midbrain.
Cerebral Peduncles
The cerebral peduncles are located on the front side of the midbrain, and due to their shape and structure, the midbrain is able to efficiently transmit signals throughout the body. Nerve fibers in this part of the brain are critical for communication between the cerebral cortex and other brain areas. The substantia nigra in the cerebral peduncle is part of the basal ganglia system and has profound effects on motor planning and learning.
Loss of dopamine neurons in the substantia nigra contributes to the progression of Parkinson's disease.
Blood supply and development
The blood supply to the midbrain mainly comes from the superior cerebellar artery, the central branch of the basilar artery, and the posterior cranial artery. As the embryo develops, the midbrain arises from the second vesicle of the neural tube and undergoes no further segmentation. This allows the midbrain to maintain its original shape and function while other brain regions develop, which is also of great significance in evolution.
Function of the midbrain
Overall, the midbrain plays a key role in the neural pathways of the motor system. Dopamine produced in this structure is directly related to the animal's movement, excitement and motivation, which has also been confirmed in experimental mice.
The midbrain is not only a structure shared by the oldest vertebrates, but also one of the core parts of the human brain.
However, as the study of the midbrain becomes more and more in-depth, can we better understand its role and influence in our daily lives?
