Human Physiology Notes P2

The complexity of regulation of genes provide a lot of variability in symptoms. Transporter brings T4 into cell, T3 transported into a nerve cell where it binds to nuclear receptor. Nerve cells do not have the ability to convert T4 to T3, glial cells do this converting and the nerve cells have to take up the T3 that they have converted. If T3 does not get into nerve cells, there will be severe muscular deficiencies. Cell specificity of steroids depends on the presence of a receptor: for example, there must be an estrogen receptor for a cell to be affected by the presence of estrogen. The gene that codes for TRH is relatively small, and there are five copies of it in its precursor. When cut, the intervening pieces of protein become available. TRH mRNA is more plentiful than the TRH peptides.