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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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

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]
Farlex Partner Medical Dictionary © Farlex 2012

midbrain

The part of the brain stem located below the cerebral cortex (joining the diencephalon (thalamus and hypothalamus)) and above the hindbrain (arising from the pons/metencephalon).

Components
Tectum/corpora quadrigemina, tegmentum, cerebral aqueduct, cerebral peduncles, substantia nigra, various nuclei and fasciculi.

Functions
Associated with motor pathways via the basal ganglia; motivation and habituation via dopaminergic pathways via substantia nigra; helps relay information for vision and hearing.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

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]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

midbrain

or

mesencephalon

that part of the brain lying between the forebrain and hindbrain. It contains the optic lobe and is particularly concerned with hearing and sight. see FOREBRAIN, HINDBRAIN.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

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]
Medical Dictionary for the Dental Professions © Farlex 2012
References in periodicals archive ?
"Our finding that mice bred for high levels of voluntary exercise have an enlarged non-cerebellar brain mass and an enlarged midbrain, but do not show a statistically significant increase in overall brain mass or volume supports the mosaic theory of brain evolution," Garland said.
"It is possible that individual differences in the propensity or ability for exercise in humans are associated with individual differences in the size of the midbrain, but no one has studied that," Garland said.
We evaluated the expression of OX-42 protein in thalamus and midbrain tissues as described above.
We also analyzed the expressions of BDNF protein in thalamus and midbrain tissues as described above.
The aim of this study was to evaluate the involvements of central glial cells (GFAP and OX-42) and brain-derived neurotrophic factor (BDNF) in the thalamus and midbrain after CCI and after NM treatment in rats.
Our results revealed increases in glial cells (GFAP and OX-42) in the thalamus and midbrain after CCI injury relative to the control groups (i.e., the naive and sham groups).
In the animals treated with neural mobilization (NM CCI), we found decline in BDNF expression (36% in the thalamus and 41% in the midbrain) compared to the animals that did not receive treatment.
Embryonic chick midbrain MM cultures were exposed to iAs (1-5 [micro]M), Cd (1-8 [micro]M), phenytoin (100 [micro]M), or cortexolone (2 [micro]M).
To examine the links between the GR pathway and these two separate metals, we further assessed the toxicity of iAs or Cd in midbrain MM culture, an established method to assess the effects of developmental toxicants (L'Huillier et al.
In addition, iAs- and Cd-induced neurodevelopmental toxicity were partially or completely protected via GR pathway inhibition assessed using the midbrain MM culture assay.
An in vitro assay for teratogens with cultures of rat embryo midbrain and limb bud cells.