Cell nucleus
The nucleus is the largest cellular organelle in animal cells.
In mammalian cells, the average diameter of the nucleus is approximately 6 micrometres (µm), which occupies about 10% of the total cell volume. The viscous liquid within it is called nucleoplasm (or karyolymph), and is similar in composition to the cytosol found outside the nucleus. It appears as a dense, roughly spherical or irregular organelle. The composition by dry weight of the nucleus is approximately: DNA 9%, RNA 1%, Histone Protein 11%, Residual Protein 14%, Acidic Proteins 65%.
Nucleus incertus
The nucleus incertus has a bilateral structure which sits near the brainstem, and is often also called 'nucleus O'. It consists of mostly ascending GABAergic projection neurons and glutamatergic neurons which innervate a broad range of forebrain regions involved in behavioural activation and the response to stress.