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.
The name oxygen was created by Antoine Lavoisier who incorrectly believed that oxygen was necessary to form all acids. Oxygen is the third most abundant element in the universe and makes up nearly 21% of the earth's atmosphere. Oxygen accounts for nearly half of the mass of the earth's crust, two thirds of the mass of the human body and nine tenths of the mass of water.