1 Extrapyramidal tracts â These tracts originate in the brain stem, carrying motor fibres to the spinal cord. 2  They are responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion.his article is about the descending tracts of the central nervous system. The descending tracts are the pathways by which motor signals are sent from the brain to lower motor neurones. The lower motor neurones then directly innervate muscles to produce movement.
The word oxygen comes from Greek words: oxus (acid) and gennan (generate). Oxygen comes to earth from all parts of the universe in meteorites. It is also found in minerals and plants that grow on the earth and other planets.
Early organisms created oxygen from other gases in the atmosphere.   More specifically, the methane atmosphere on Earth was supplanted  by oxygen generated by microorgani â¦ sms in the oceans. Today, the  vast majority of our oxygen comes from the ocean-mainly plants.   Earth came to have a oxygen atmostphere because that is the way God invisoned it, so thats how he made it.+ 13 others found this useful.t is difficult to answer this question because it mainly depends on the size and mass of an object. Most space debris sizes, almost like a land-rover, need hypersonic speed t â¦ o enter the earth's atmosphere. This speed is classified as Mach 5 and over.