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The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. [2] It consists of the cerebral peduncles , tegmentum , and tectum . It is functionally associated with vision, hearing, motor control, sleep and wakefulness, arousal ( alertness ), and temperature regulation.
Neurobiologists have often had great difficulty distinguishing the VTA in humans and other primate brains from the substantia nigra (SN) and surrounding nuclei. Originally, the ventral tegmental area was designated as a ‘nucleus’, but over time ‘area’ became the more appropriate term used because of the heterogeneous cytoarchitectonic features of the region and the lack of clear ...
The mesolimbic pathway transmits dopamine from the ventral tegmental area (VTA), which is located in the midbrain, to the ventral striatum, which includes both the nucleus accumbens and olfactory tubercle. [5] [6] The "meso" prefix in the word "mesolimbic" refers to the midbrain, or "middle brain", since "meso" means "middle" in Greek.
The mesolimbic pathway and its positioning in relation to the other dopaminergic pathways. The mesolimbic pathway is a collection of dopaminergic (i.e., dopamine-releasing) neurons that project from the ventral tegmental area (VTA) to the ventral striatum, which includes the nucleus accumbens (NAcc) and olfactory tubercle. [9]
Cross-section of the midbrain. Tectum. Corpora quadrigemina. Inferior colliculi; Superior colliculi; Pretectum; Tegmentum. Periaqueductal gray; Rostral interstitial nucleus of medial longitudinal fasciculus; Midbrain reticular formation; Dorsal raphe nucleus; Red nucleus; Ventral tegmental area. Parabrachial pigmented nucleus; Paranigral ...
Stimulation of the periaqueductal gray matter of the midbrain activates enkephalin-releasing neurons that project to the raphe nuclei in the brainstem. 5-HT released from the raphe nuclei descends to the dorsal horn of the spinal cord where it forms excitatory connections with the inhibitory interneurons located in Laminae II (aka the substantia gelatinosa).
The midbrain tegmentum is also an important part of the dopaminergic system which is essential for feelings of reward and pleasure. Two regions in the midbrain tegmentum are of particular interest. The first one is the substantia nigra which is an important part of the nigrostriatal pathway. This pathway serves to coordinate motor movements and ...
The brainstem, resembling a stalk, attaches to and leaves the cerebrum at the start of the midbrain area. The brainstem includes the midbrain, the pons, and the medulla oblongata. Behind the brainstem is the cerebellum (Latin: little brain). [7] The cerebrum, brainstem, cerebellum, and spinal cord are covered by three membranes called meninges.