2.75 Describe the role of ADH in regulating the water content of the blood

THIS FINALLY MAKES SENSE.

Excess or lack of water is detected in the brain by the hypothalamus. It causes the pituitary gland to produce ADH (anti-diuretic hormone). It travels through the blood stream and into the kidneys - specifically, into the collecting duct. According to the water levels in the body, it will give a signal to either make the membrane (walls) more porous. Increased levels of ADH are typically secreted when there is lack of water in the body, because it makes the membrane walls more porous.

The more porous the membrane is, the more water is absorbed. 

It causes urine to be more concentrated and of less quantity. It is also typically a yellowish color. If there is too much water, the levels of ADH will lower and the opposite effects will happen; the membrane becomes less porous, less water is absorbed and urine is clear and less concentrated (and more in quantity)

FOR STUDYING
A ridiculously long and rather unhelpful acronym:

Brain detects water levels
Hypothalamus (does this)
Pituitary gland produces ADH
(B)lood stream carries hormone
(K)idneys receive hormone
(C)ollecting duct specifically
(M)membrane 
Porous (refers to membrane)
Water
(A)bsorbed
Returned to blood stream

BHPBKCMPWAR (long version)
BHPPWR (simplified)

A very simplified acronym of the process:

Detect
Produce ADH
Carry
Recieve
Collecting duct
Porous (membrane)
Absorbed
Returned (to blood stream)

DPCRCPAR
(Daddy Paced Carol's Room Cindy Passed Away Restfully)

For the super long acronym, here is a suggestion for remembering it (refers to Harry Potter)
Brave
Harry
Painted
Blue
Kittens
Cursing
Merrily
Patently
Wearing 
Red