Describe how a fall in the water potential of the blood results in an increase in the concentration of antidiuretic hormone (ADH) in the blood.
$ADH$ is carried in the blood to the cells of the collecting duct in the kidney. Fig. 1.1 shows a diagram of how $ADH$ acts on the cells of the collecting duct.
When $ADH$ binds to the $ADH$ receptor, it sets off reactions inside the cell. One of the earliest reactions is the formation of cyclic AMP ($cAMP$). State the name used for molecules such as $cAMP$ in cell signalling.
Describe the function of the vesicle when the kinase enzyme is stimulated.
On Fig. 1.1, add arrows to show the direction of movement of water molecules after the collecting-duct cells have responded to $ADH$.
Some people have a rare kidney disorder in which $ADH$ is unable to bind to $ADH$ receptors. Suggest the effects of this disorder on osmoregulation.