What is the function of the posterior commissure?
Posterior commissure. The posterior commissure (PC) is a transversely-oriented commissural white matter tract that connects the two cerebral hemispheres along the midline. It is a very important anatomical landmark which is thought to play a role in the visual system, however its functions are still largely unknown.
Where is the posterior commissure labelled at center top?
The posterior commissure is labelled at center top. The posterior commissure (also known as the epithalamic commissure) is a rounded band of white fibers crossing the middle line on the dorsal aspect of the rostral end of the cerebral aqueduct. It is important in the bilateral pupillary light reflex .
What is the posterior commissure of the labia major?
For the female genital structure, see Posterior commissure of labia majora. The posterior commissure (also known as the epithalamic commissure) is a rounded band of white fibers crossing the middle line on the dorsal aspect of the rostral end of the cerebral aqueduct. It is important in the bilateral pupillary light reflex.
Where is the posterior commissure in the heart?
Anatomically, the posterior commissure is located in the posterior part of the third ventricle, composing the roof, floor, posterior wall and both lateral walls [27]. Its fibres interconnect the pretectal nuclei thus mediating the consensual pupillary light reflex. ... ...
What does the anterior commissure connect?
The anterior commissure (also labeled ac) is a large bundle of crossing fibers, which connects the olfactory bulb and parts of the cerebrum to the same areas on the opposite side.
Where is the posterior commissure in the brain?
The posterior commissure (also known as the epithalamic commissure) is a rounded band of white fibers crossing the middle line on the dorsal aspect of the rostral end of the cerebral aqueduct. It is important in the bilateral pupillary light reflex. Sagittal cross-section of the human brain.
What does posterior commissure mean?
Medical Definition of posterior commissure : a bundle of white matter crossing from one side of the brain to the other just rostral to the superior colliculi and above the opening of the aqueduct of Sylvius into the third ventricle.
What do commissural tracts connect?
Commissural fibers of the brain, also known as commissural tracts of the brain or commissures are a type of white matter tract that cross the midline, connecting the same cortical area in opposite hemispheres (right-left hemispheric connections 3).
Is the posterior commissure part of the corpus callosum?
The corpus callosum is the largest of the side-to-side interconnections between the two hemispheres and, in general, connects analogous areas in the two hemispheres. The anterior and posterior commissures are other small bundles of interhemispheric fibers, located anteriorly and posteriorly to the corpus callosum.
What is the anterior and posterior commissure?
The anterior commissure works with the posterior commissure to link the two cerebral hemispheres of the brain and also interconnects the amygdalae and temporal lobes, contributing to the role of memory, emotion, speech and hearing. It also is involved in olfaction, instinct, and sexual behavior.
What is the main commissure connecting the cerebral hemispheres?
The corpus callosum is the largest commissural tract in the human brain. It consists of about 200-300 million axons that connect the two cerebral hemispheres. The corpus callosum is essential to the communication between the two hemispheres.
What is commissure meaning?
Definition of commissure 1 : a point or line of union or junction especially between two anatomical parts (such as adjacent heart valves) 2 : a connecting band of nerve tissue in the brain or spinal cord.
What is posterior commissure of larynx?
The flat, front-facing surface of the glottic aperture that lies between the vocal cord posterior ends.
What are the 3 commissures?
They comprise the anterior commissure, the hippocampal commissure, and the corpus callosum.
Which type of tract connects the two hemispheres of the cerebrum?
The corpus callosum is a white matter tract that connects the cerebral hemispheres, facilitating interhemispheric connectivity.
What is commissure meaning?
Definition of commissure 1 : a point or line of union or junction especially between two anatomical parts (such as adjacent heart valves) 2 : a connecting band of nerve tissue in the brain or spinal cord.
What is posterior commissure hypertrophy?
Conclusion: Posterior commissure hypertrophy can be used as a screening tool for diagnosis of LPR but cannot be used reliably as a clinical marker for response to therapy.
What is the GREY matter?
Grey matter contains most of the brain's neuronal cell bodies. The grey matter includes regions of the brain involved in muscle control, and sensory perception such as seeing and hearing, memory, emotions, speech, decision making, and self-control.
What are the cerebellum's functions?
The cerebellum is important for making postural adjustments in order to maintain balance. Through its input from vestibular receptors and proprioceptors, it modulates commands to motor neurons to compensate for shifts in body position or changes in load upon muscles.
What is the posterior commissure?
The posterior commissure is a small fasciculus that decussates in the inferior pineal lamina, and corresponds to a white matter tract almost completely surrounded by gray matter that crosses the midline just dorsal to the cerebral aqueduct . The posterior commissure, along with the pineal gland, habenular commissure, ...
What are the nuclei of the PC?
There are a number of small nuclei associated with the PC, these lie rostral to the superior colliculi. Amongst others these include the nucleus of Darkschewitscz and Cajal. As they decussate, the fibers from these nuclei contribute to form the posterior commissure.
What are the connections of the posterior commissure?
AIM: The connections of posterior commissure are defined. Its fibers mediate the consensual light reflex by interconnecting the pretectal nuclei. The fiber connections from the thalamic, pretectal, superior colliculus and the habenular nuclei are known, but they have not been shown anatomically. The present study is a fiber dissection study to define the anatomy of the posterior commissure. MATERIAL and METHODS: Twenty formalin-fixed sheep heads were used in the study. The specimens were fixed in 10% formalin solution for 3 weeks. The arachnoidal and vascular structures were removed by using a surgical microscope magnification (x6-x40) and brains were again fixed for 4 weeks at -20 degrees C. The fiber dissections were performed at Marmara University, Rhoton Laboratory. Also, a radiological tractographic study was carried on five healthy volunteers to see the posterior commissure cortical connections. RESULTS: In fifteen sheep brains, the dimensions of the posterior commissure were measured as 1.36 mm (range 0.5-2.5 mm) width, and as 4.6 mm (range 3-6 mm) length. In the dissection study, a frontotemporooccipital fascicle was observed to connect with the fibers of the posterior comnnissure. Diffusion tensor imaging scans showed the frontotemporooccipital tract to extend to posterior commissural region. CONCLUSION: To our knowledge, this is the first anatomical and tractographic study regarding the posterior commissure. However, further human cadaveric studies are necessary.
What gland is the posterior commissure of a sheep?
A, B) Sagittal sections of the sheep brain showing the posterior commissure under the pineal gland (red arrows).
Which connectons are known but have not been found?
nucle. The fber connectons from the thalamc, pretectal, superor collculus and the habenular nucle are known, but they hav e not been
How do axons navigate the brain?
Growing axons navigate through the developing brain by means of axon guidance molecules. Intermediate targets producing such signal molecules are used as guideposts to find distal targets. Glial, and sometimes neuronal, midline structures represent intermediate targets when axons cross the midline to reach the contralateral hemisphere. The subcommissural organ (SCO), a specialized neuroepithelium located at the dorsal midline underneath the posterior commissure, releases SCO-spondin, a large glycoprotein belonging to the thrombospondin superfamily that shares molecular domains with axonal pathfinding molecules. Several evidences suggest that the SCO could be involved in the development of the PC. First, both structures display a close spatiotemporal relationship. Second, certain mutants lacking an SCO present an abnormal PC. Third, some axonal guidance molecules are expressed by SCO cells. Finally, SCO cells, the Reissner's fiber (the aggregated form of SCO-spondin), or synthetic peptides from SCO-spondin affect the neurite outgrowth or neuronal aggregation in vitro.
What is the posterior commissure?
The posterior commissure is the inferior lamina or stalk of the pineal gland and is important in language processing and connects the language processing centres of both cerebral hemispheres. It is closely related in function to the splenium of the corpus callosum, and injury to it may lead to disorders such as alexia.
Where is the anterior commissure located?
The anterior commissure is located in the anterior wall of the third ventricle at the upper end of the lamina terminalis. It runs across the midline in front of the anterior columns of the fornix, above the basal forebrain and beneath the medial and ventral aspect of the anterior limb of the internal capsule.
What is the commissure of the fornix?
Commissure of fornix. The hippocampal commissure, or commissure of fornix, is a bundle of fibres interconnecting the hippocampi of the two cerebral hemispheres. More specifically, this commissure connects a part of the body of the fornix called the crus on both sides of the midline.
What is the superior lamina of the pineal body called?
Habenular commissure. Habenular commissure (sagittal view) The superior lamina or stalk of the pineal body is called the habenular commissure and connects the habenular nuclei of the two cerebral hemispheres. Thus it is also a vital part of the epithalamus.
What are the fibre bundles that connect the left and right sides of the brain?
In most cases, these interconnecting fibres form recognisable bundles referred to as commissures. Thus, commissural pathways are fibre bundles interconnecting similar regions or structures in the left and right sides of the midbrain, spinal cord, cerebral hemispheres or cerebellum.
Where is the postcommissural fornix?
The remaining three being the postcommissural fornix lying behind the anterior commissure, the precommissural fornix, which descends anteriorly to the anterior commissure, and a bundle of fibres running above the splenium of the corpus callosum. This bundle of running fibres is referred to as the dorsal fornix.
Where are the commissural pathways located?
The most recognised and well understood of the commissural pathways are the habenular commissure, anterior commissure, posterior commissure, corpus callosum, and the hippocampal commissure or commissure of the fornix, all of which are located in the cerebral hemispheres.
