Fast heart rate: Tachycardia means fast heart beat. Sinus node is the structure where normally heart rhythm and beat is originated, and it naturally responds to stimuli when the heart needs to beat faster. Inappropriate sinus tachycardia is when the heart is beating fast, when it shouldn't. ...Read more.
The atom is the smallest subdivision of an element which still retains the properties of that element. In fact, a very good definition of an atom is: the smallest part of an element that can enter into a chemical combination. There are around 118 elements known to man, of which 20-30 are really, really important.he parallel definition (to the element one above) for the molecule is: the smallest part of a compound that can enter into a chemical combination. Another definition, equally good, is that a molecule is the smallest stable part of a compound. Water is a typical example of a compound.
Most of the substances around us consist of molecules and are called compounds of various elements. Molecules are the smallest particle of a compound that has all the chemical properties of that compound. They are made up of two or more atoms, either of the same element or of two or more different elements.olecules and compounds contain their constituent elements in specific proportions that are characteristic of the compound. For example, water (H 2 O), a well known and simple compound, contains hydrogen and oxygen at a ratio of 2 to 1.