Ads
related to: crossing the midline activities pdf worksheet freeteacherspayteachers.com has been visited by 100K+ users in the past month
- Resources on Sale
The materials you need at the best
prices. Shop limited time offers.
- Lessons
Powerpoints, pdfs, and more to
support your classroom instruction.
- Worksheets
All the printables you need for
math, ELA, science, and much more.
- Projects
Get instructions for fun, hands-on
activities that apply PK-12 topics.
- Resources on Sale
Search results
Results from the WOW.Com Content Network
This article is about the optic chiasm of vertebrates, which is the best known nerve chiasm, but not every chiasm denotes a crossing of the body midline (e.g., in some invertebrates, see Chiasm (anatomy)). A midline crossing of nerves inside the brain is called a decussation (see Definition of types of crossings).
In mammals and birds and other vertebrates with frontal eyes, the optic nerves do blend in the optic chiasm, and only part of the nerve fibres cross the midline. [5] The drawings of Cajal suggest that the axons of the optic nerve may branch in the optic chiasm, and thus give off a branch both in the ipsi- and contralateral optic tract. [ 5 ]
The anterior commissure (also known as the precommissure) is a tract that connects the two temporal lobes of the cerebral hemispheres across the midline, and placed in front of the columns of the fornix.
The inability of these axons to cross the midline results in anomalous axonal guidance and front-to-back projections within each hemisphere, rather than connecting between the hemispheres in the normal corpus callosum. These longitudinal callosal fascicles were originally described by Moriz Probst in 1901 by gross anatomical observation. [1]
Decussation is used in biological contexts to describe a crossing (due to the shape of the Roman numeral for ten, an uppercase 'X' , from Latin decem 'ten' and as 'as'). In Latin anatomical terms, the form decussatio is used, e.g. decussatio pyramidum. Similarly, the anatomical term chiasma is named after the Greek uppercase 'Χ' .
At the pyramids' most caudal end, the corticospinal axons decussate (or cross over) the midline and continue down the spinal cord on the contralateral side. The fibers that decussated will go down the lateral corticospinal tract while the fibers that did not decussate will travel down the anterior corticospinal tract .
Their axons cross over to the other side of the medulla and are now named as the internal arcuate fibers, that form the medial lemniscus on each side. This crossing over is known as the sensory decussation. At the medulla, the medial lemniscus is orientated perpendicular to the way the fibres travelled in their tracts in the posterior column.
The oculomotor nerve crosses the midline before leaving the central nervous system. The trochlear nerve crosses the midline in a chiasma on the dorsal side and the abducens innervates an eye muscle on the same side. [29]: Fig. 17.8 In the light of the axial twist theory, this complicated pattern can be understood.
Ads
related to: crossing the midline activities pdf worksheet freeteacherspayteachers.com has been visited by 100K+ users in the past month