mesencephalon


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Related to mesencephalon: metencephalon, rhombencephalon, diencephalon

mesencephalon

 [mes″en-sef´ah-lon]
1. the short part of the brainstem just above the pons; it contains the nerve pathways between the cerebral hemispheres and the medulla oblongata, as well as nuclei (relay stations or centers) of the third and fourth cranial nerves. The center for visual reflexes, such as moving the head and eyes, is located here.
The mesencephalon (midbrain). From Applegate, 2000.
2. the middle of the three primary brain vesicles of the embryo; called also midbrain. adj., adj mesencephal´ic.

mes·en·ceph·a·lon

(mes-en-sef'ă-lon), [TA]
That part of the brainstem developing from the middle of the three primary cerebral vesicles of the embryo (the caudal of these being the rhombencephalon or hindbrain, the rostral the prosencephalon or forebrain). In the adult, the mesencephalon is characterized by the unique conformation of its roof plate, the lamina tecti (tectal plate [TA] or quadrigeminal plate [TAalt]). composed of the bilaterally paired superior and inferior colliculus, and by the massive paired prominence of the crus cerebri at its anterolateral (ventrolateral) surface. On transverse section, its patent central canal, the cerebral aqueduct, is surrounded by a prominent ring of gray matter poor in myelinated fibers; the periaqueductal gray is adjoined by the myelin-rich mesencephalic tegmentum, and covered posteriorly (dorsally) by the mesencephalic tectal plate. Prominent cell groups of the mesencephalon include the motor nuclei of the trochlear and oculomotor nerves, the red nucleus, and the substantia nigra.
Synonym(s): midbrain vesicle ☆ , midbrain
[mes- + G. enkephalos, brain]

mesencephalon

(mĕz′ĕn-sĕf′ə-lŏn′, mĕs′-)
n.
The midbrain.

mes′en·ce·phal′ic (-sə-făl′ĭk) adj.

mesencephalon

The midbrain, which contains the cerebral peduncles and tectum (tectal lamina) and the corpora quadrigemina (the two superior and two inferior colliculi).

mes·en·ceph·a·lon

(mes'en-sef'ă-lon) [TA]
That part of the brainstem developing from the middle of the three primary cerebral vesicles of the embryo. In an adult, the mesencephalon is characterized by the unique conformation of its roof plate, the lamina of the mesencephalic tectum, composed of the bilaterally paired superior and inferior colliculi, and by the massive paired prominence of the crus cerebri at its ventral surface. Prominent cell groups of the mesencephalon include the motor nuclei of the trochlear and oculomotor nerves, the red nucleus, and the substantia nigra.
Synonym(s): midbrain.
[G. mes- middle + G. enkephalos, brain]

mesencephalon

The middle section of the embryonic brain.

mesencephalon

see MIDBRAIN.

mes·en·ceph·a·lon

(mes'en-sef'ă-lon) [TA]
That part of the brainstem developing from the middle of the three primary cerebral vesicles of the embryo. In an adult, the mesencephalon is characterized by the unique conformation of its roof plate, the lamina of the mesencephalic tectum, composed of the bilaterally paired superior and inferior colliculi, and by the massive paired prominence of the crus cerebri at its ventral surface.
Synonym(s): midbrain.
[G. mes- middle + G. enkephalos, brain]
References in periodicals archive ?
Supratentorial structures ventral to the mesencephalon are most susceptible to central incisural shift.
(T, thalamus; M, mesencephalon; BA, basilar artery; PCA, posterior cerebral artery; P1, first arterial segment of the PCA; AOP, artery of Percheron; ICA, internal carotid artery.)
All patients with the classic form of the disease (n=6) showed involvement of a wide range of brain parenchyma, including the basal ganglia in six cases, the cerebellum, mesencephalon, pons, and supratentorial area in five cases, and the thalamus in four cases (Fig.
The column on the right has the convention of colors: (1) Frontal Lobe; (2) Insula; (3) Limbic Lobe; (4) Hippocampal Formation; (5) Occipital Lobe; (6) Parietal Lobe; (7) Temporal Lobe; (8) Amygdala; (9) Basal Ganglia; (10) Diencephalon; (11) Mesencephalon; (12) Hindbrain.
It must be considered that several other brain areas are also affected, some even before the mesencephalon. Among those structures, the mesolimbic pathway, the locus coeruleus, and the raphe nuclei can be damaged.
Scientifically called the mesencephalon, it is the portion of the brain stem that connects the forebrain and the hind brain.
In acute intoxication with lithium administered intraperitoneally by a single nonlethal dose of 250.16 mg/kg, and subchronically, by 4 administrations of 61.904 mg/kg LiCl over the course of 8 days, the vacuolization of the brain tissue and zones of spongiosis were observed in different brain regions, including cerebral cortex, cerebellum, medulla oblongata, mesencephalon, thalamus, and pons [32].
Effect of tooth pulp and periaqueductal central gray stimulation on the expression of genes encoding the selected neuropeptides and opioid receptors in the mesencephalon, hypothalamus and thalamus in rats.
PEG3 plays a critical role in brain development, with expression mainly in the mesencephalon and pituitary gland; in the adult brain PEG3 is found primarily in the hypothalamus and the pituitary gland (Li et al.
For example, PET images reveal that MDD patients show greater expression of monoamine oxidase A (MAO-A) in the PFC, temporal cortex, hippocampus, thalamus, accumbens nucleus (NAc) and mesencephalon. (39) These discoveries imply that the greater degradation rate of 5-HT and NA is one of the pathophysiologic mechanisms that attenuate monoaminergic transmission.