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.
Category: Biology Published: January 5, 2013. All of earth's oxygen does not come from trees. Rather, the atmospheric oxygen that we depend on as humans comes predominantly from the ocean. According to National Geographic, about 70% of the oxygen in the atmosphere comes from marine plants and plant-like organisms. These ocean-living plants release molecular oxygen as a waste product of photosynthesis (as do most plants).