Organic nutrients (glucose,
amino acids) all reabsorbed
Water, ions continuously
regulated
Methods of Reabsorption
Active Transport: ATP used to move molecules across membrane.
Sodium
Secondary Active Transport: when Active Transport of one molecule
helps to move another molecule across a membrane (via a co-
transporter).
Glucose, amino acids, vitamins
Passive Transport: a concentration gradient drives diffusion of a
molecule across a membrane.
Water, ions
Passive Transport of Water
Obligatory water reabsorption
Facultative water reabsorption
Water reabsorbed
regardless
of state of over- or under-
hydration of body
Location: PCT, nephron loop
(descending limb)
Water reabsorption that
depends on ADH (hormone-
controlled)
Location: Collecting duct
Hormonal Regulation of Tubular
Reabsorption
Reabsorption of water and solutes only controlled in DCT and
Collecting Duct.
Hormone
Function
Antidiuretic Hormone
(ADH)
During dehydration, ADH increases -> decreases urine output by causing more
reabsorption of water in CD (opposite in over-hydration)
Aldosterone
Increases Na
+
reabsorption in DCT & CD
Goal is to increase blood volume and pressure
Atrial Natiuretic Peptide
(ANP)
Decreases Na
+
reabsorption in CD
Opposite to Aldosterone
Parathyroid Hormone
(PTH)
Increases reabsorption of Ca
2+
in DCT
