Unit 5 Lecture 36 Flashcards
What % of solutes and water was reabsorbed into blood by the end of the DCT
90-95%
What are the 2 cells found in the collecting ducts?
principal cells and intercalated cells
Function of principal cells
- reabsorb Na+ and water
- secrete K+
What hormones effect the functions of principal cells and what do they individually control?
aldosterone - effects Na+ and K+
ADH - effects water
Function of intercalated discs
- reabsorb K+ and bicarbonate ions
- secrete H+
What direction does Na+ move across a membrane?
Filtrate –> blood
What does Na+ first pass through to get into a principal cell?
leakage channels
What does Na+ pass through to leave principal cells into ISF?
Na+/K+ pumps
What direction does K+ move across a membrane?
ISF –> filtrate
What two things must K+ pass through (in order) to get into filtrate?
- Na+/K+ pump
- K+ leakage channel
(opposite of Na+)
What does aldosterone do to principal cells and how??
Increases Na+/ water reabsorption and K+ secretionby adding new pumps and channels into membrane
What does ADH do to principal cells and how?
Inceases water reabsorption by inserting aquaporins into apical membrane
Function of intercalated cells in the collecting duct?
regulates pH of body fluids by secretion of H+ and reabsorption of HCO3-
What is needed in intercalated discs to secrete H+ and reabsorb HCO3- and what does it make?
CO2 and water
*they bond together to make carbonic anhydrase –> carbonic acid which then dissociates into H+ and HCO3-
What direction does H+ move from intercalated cells?
intercalated cells –> filtrate
How does H+ pass through the membrane into filtrate?
proton pumps (ATPases)
Is urine acidic or basic?
ACIDIC
How are acidic H+ buffered once it gets into filtrate?
bonds with either (HPO4)2- or NH3
What does CO2 and water make when bonded together in intercalated cells?
carbonic anhydrase –> carbonic acid
What direction does bicarbonate (HCO3-) move across intercalated cells?
Intercalated cell –> peritubular capillary
What must bicarbonate travel through to get to blood?
Cl-/HCO3- antiporters
What direction does Cl- move across Cl-/HCO3- antiporters?
ISF –> intercalated cells
What happens to pH when HCO3- enters blood?
pH rises
What do intercalated cells do when blood pH drops (gets more acidic)?
- forms more carbonic acid
- secretes more H+ into filtrate
- exchanges more Cl- for HCO3-
- More HCO3- enters blood, raising blood pH
Why is it important that intercalated cells control blood pH?
Although they are slow at changing blood pH vs. respiratory system, they are they only system that can counter act the acidity of nonvolatile acids like sulfuric acid by excreteing H+ in urine
Define diuretics
substances that slow the reabsorption of water in blood –> greater urine flow rate
What are 3 examples of diretics?
Caffeine, Alcohol, meds
What does caffeine do urine production?
Inhibits Na+ reabsorption
What type of water reabsorption process is inhibited due to caffeine?
obligatory water reabsorption
What does alcohol do to urine production?
Inhibits secretion of ADH
What type of water reabsorption process is inhibited due to alcohol?
facultative water reabsorption
What does some prescription meds do to urine production?
effects the PCT, loop of Henle or DCT
Define micturition
urination
What type of fibers cause detrusor muscles in the urinary bladder to contract and initiate micturition?
parasympathetic fibers
What must the internal and external sphincters do for micturition?
relax
What type of control do we have over the internal and external sphincters?
internal - involuntary (smooth muscle)
external - voluntary (skeletal muscle)
What brain structure can initiate or delay micturition for a period of time?
Cerebral cortex
