Physiology 4 - Reabsorption and Secretion Flashcards
The vast majority of reabsorption occurs at which point in the neprhon?
Proximal convoluted tubule
What percentage of water and salt is reabsorbed by the kidneys?
99%
Which two substances are normally 100% reabsorbed in the kidneys?
Glucose and amino acids
What percentage of urea is reabsorbed in the kidneys?
50%
What is the osmolarity of tubular fluid going into the proximal convoluted tubule?
300mosmol/l
What is the osmolarity of tubular fluid coming out of the proximal convoluted tubule?
300mosmol/l
Where are glucose and amino acids reabsorbed?
Proximal convoluted tubule
Where is creatinine secreted into the nephron?
Proximal convoluted tubule
Where are drugs to be excreted secreted into the nephron?
Proximal convoluted tubule
Where are hydrogen ions secreted into the nephron?
Proximal and distal convoluted tubules
Where are potassium ions secreted into the nephron?
Distal convoluted tubule
‘Energy from the hydrolysis of ATP is used to move the substance against its concentration gradient’ describes which type of membrane transport?
Primary active transport
‘The carrier molecule is transported coupled to the concentration gradient of an ion’ describes which type of membrane transport?
Secondary active transport
‘Passive carrier mediated transport of a substance down its existing concentration gradient within the cell membrane’ describes which type of membrane transport?
Facilitated transport
Under normal circumstances, in what direction is the sodium concentration gradient?
Inward
Under normal circumstances, in what direction is the potassium concentration gradient?
Outward
Sodium ions are reabsorbed in all regions of the nephron except where?
Descending limb of the loop of Henle
The reabsorption of sodium is driven by the presence of the Na+/K+ pump at which membrane of the cell?
Basolateral
What type of transporter is the Na+/K+ ATPase pump?
Primary active transporter
Within the Na+/K+ ATPase, does sodium enter or exit the cell?
Exit
Within the Na+/K+ ATPase, does potassium enter or exit the cell?
Enter
Sodium is positively charged and so when it moves across a cell via the transcellular route in the proximal convoluted tubule it sets up an electrochemical gradient for the passive reabsorption of what via the paracellular route?
Chloride
Via what route is water reabsorbed in the proximal convoluted tubule?
Paracellular
Why is there no overall change in osmolarity at the beginning and end of the proximal convoluted tubule?
Water and salt are reabsorbed in equal concentrations
When glucose is reabsorbed in the proximal convoluted tubule via the transcellular route, this sets up an osmotic gradient for the reabsorption of what via the paracellular route?
Water
At what blood glucose level will the transport mechanisms in the proximal convoluted tubule become saturated?
10-12mmol/l
2/3rds of water and salt are reabsorbed where in the nephron?
Proximal convoluted tubule
Which segment of the loop of Henle is highly permeable to water?
Descending limb
Which segment of the loop of Henle is relatively impermeable to water?
Ascending limb
Salt (i.e. sodium and chloride) is reabsorbed in which segment of the loop of Henle?
Ascending limb
Which segment of the loop of Henle does not reabsorb salt?
Descending limb
Is salt reabsorption in the thin ascending loop of Henle active or passive?
Passive
Is salt reabsorption in the thick ascending loop of Henle active or passive?
Active
Where is the Na+/K+/Cl- triple co-transporter found?
Thick ascending loop of Henle
On which membrane of the cell is the Na+/K+/Cl- triple co-transporter found?
Apical
What drug group blocks the Na+/K+/Cl- triple co-transporter?
Loop diuretics
What is the tonicity of tubular fluid compared to the interstitial fluid when it leaves the loop of Henle?
Hypotonic
If a person is dehydrated, what happens to the levels of ADH?
Increased
Describe the urine which is produced when a person is dehydrated?
Small volumes of concentrated urine
If a person is over-hydrated, what happens to the levels of ADH?
Decreased
Describe the urine which is produced when a person is over-hydrated?
Large volumes of dilute urine
Hormones which affect reabsorption act on which parts of the nephron?
Distal convoluted tubule and collecting ducts