Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
58 Cards in this Set
- Front
- Back
|
Why is it important to keep balance of Na and water?
|
Critical for blod pressure blody volume and maintenance of life
|
|
|
Does the body salt or water content vary a lot?
|
No, stays ~constant despite the highly variable intake
|
|
|
How does the water output vary? NaCl output?
|
Water output: vary depending on intake :0.4 to 25L/day
NaCl output: vary depending on intakes; 0.05 to 25g/day |
|
|
What is insensible loss?
How much does it contribute to the total output? |
Loss of water from the skin and lungs (but not sweating)
->contributes to 900mL |
|
|
What is the greatest loss of NaCl?
|
Through the urine (10 out of 10.5 total g)
|
|
|
Where is bood filtered?
|
In Bowman's space at the glomerulUS
|
|
|
What is the filtrate?
|
Cell free plasma
**Needs to be modified before becoming the final urine |
|
|
What is absorption?
|
Solute or water movement from the tubule (urine) back to the blood
|
|
|
What is secretion?
|
Movement of solute from blood or the cel interior into the tubukle lumen (urine)
|
|
|
Are Na and water freely filtered? Where are they reabsorbed? How much is reabsorbed?
|
Yes, freely filtered from the glomerulus to the tubule
Reabsorbed in the nephron, 99% |
|
|
Where is most of the sodium and water reabsorbed?
|
Proximal tubule: ~2/3
|
|
|
How much Na is reabsorbed in the TAL?
DCT? CD? |
TAL:25%
DCT: 4-5% CD: ~3% |
|
|
Is water reabsorbed in the TAL?
|
NO
|
|
|
Is Na reabsorption an active or passive process?
|
Active
Na isreabsobed in all tubular segments EXCEPT the descending limb of the loop of Henle |
|
|
By which process is water reabsorbed? What is it dependent on?
|
Reabsorbed by Diffusion
Depends on Na reabsorption |
|
|
Describe the tubule cell
|
One-cell thickness
Has one side facing the urine side, one side facing the blood side |
|
|
On which side of the membrane does the active Na+/K+ ATPase pump sodium out of the cell? Why?
|
Pumps on the basolateral (blood side) of the membrane
Why? Keep intracellular concentration of Na low |
|
|
What hapens on the apical (lumenal/urine side) of the membrane?
|
Na moves down its gradient from the tubular lumen into the tubular epithelial cells
|
|
|
What are the mechanisms of the Proximal tuble to move Na?
|
Na+-H+ antiporter
Na-glucose co-transporter Na-aa cotransporter |
|
|
What are the mechanisms of Na+ transport in the cortical collecting duct?
|
Diffusion via Na+ channel
-> can be btw cells or when no E is required (through a channel) |
|
|
What are the 3 steps involved in Na reabsorption?
|
1) Active Na transport out of the cell -> blood
2) Na goes down its gradient from the urine into the cell 3) Water moves passively out of the cell into the intestitium -> towards the blood |
|
|
What role does the proximal tubule play in reabsorption?
|
Reabsorbs the bulk of filtered small solutes
(most of the filtrate is good .: our bodies want it back) About 60% of the filtere NaCl, K, Ca and water and more than 90% of the filtered HCO3 are reabsorbed ALL glucose and aa are reabsorbed here |
|
|
How are all the glucose and aa reabsorved in the proximal tubule?
|
Na-dependent co-transport
|
|
|
What doe the late proximal tubule have?
|
Na/H exhanger
|
|
|
Where does secretion of toxins and drugs occur in the PT?
|
At the terminal portion of the proximal tubule: elimination
|
|
|
What are the other sites of Na absorption? (other than proximal tubule)
|
TAL of loop: Na-K-2Cl cotransporter
DCT: Na/Cl cotransporter Collecting duct: Na channel |
|
|
What happen to the uriniary excretion of Na if:
Na intake inc? Na intake dec? |
Na intake inc: Na excretion in urine inc
Na intake dec: Na excretion in urine dec |
|
|
What kind of solute is Na for the body?
|
The major extracellular solute
|
|
|
What happens if there are changes in the total body Na?
|
Changes in extracellular fluid volume in the interstitium and the vascular space
|
|
|
Is the [Na] in the plasma a good marker for total bodt Na?
|
No
P(Na) only reflects the relative relationship of total body Na and H2O |
|
|
What senses total body Na?
|
Baroreceptors sens total body Na as volume-intravascular filling
|
|
|
Why doesn't plasma Na reflect the total amt of sodium in the body?
|
Can have a high total body Na and accompanying water (high extracellular fluid volume and plasma vlume) or low total Na and water (low volume state), with a steady Na concentration
|
|
|
What % of BW is:
Total body water? Intracellular fluid? Extracellular fluid? |
Total: 60%
Intracell: 40% Extracell: 20% -> 3/4 ISF, 1/4 plasma |
|
|
What regulates Na excretion?
|
GFR (minor role)
Na reaborption (very important) |
|
|
Is Na excreted at the tubules?
|
NO
|
|
|
Describe GFR control of renal Na regulation.
|
Inc Na and H2O loss due to diarrhea
-> dec in plasma volume -> dec venous P -> dec venous return -> dec atrial P -> dec ventricular end-diastolic volume -> dec stroke volume -> dec cardiac output -> dec arterial BP .: Inc activity of renal sympathetic nerves (reflexes mediated by venous, atrial and arterial baroreceptors) ---> Get increased constriciton of renal afferent arterioles .: dec net GF pressure.: DEC GFR End result: DEC in Na and H2O excreted (retained to preserve blood volume) |
|
|
How does reabsorption control renal regulation of Na?
|
Hormone: Aldosterone (steroid H secreted by th e adrenal cortex, zona glomerulosa)
|
|
|
What does aldosterone do?
|
Simulates reabsorption in the DCT and CCD
|
|
|
What happens if there is no aldosterone? High aldosterone?
|
No: ~2% of filtered load is excreted (=35 g of NaCl)
High: ~0% of filterd load is excreted (Na is totally reabsorbed) |
|
|
Where does aldosterone actually act?
|
Cortical collecting duct cells
|
|
|
How does aldosterone increase Na+ reabsorption?
|
Inc upregulation of:
Na/K ATPase: increaes its activity Na channel (helps Na enter the cell) K channel ->also inc H+ secretion |
|
|
Does aldoesterone increase glucose uptake?
|
NO
Because aldosterone only works in the cortical collecting duct ->there is no Na+/glucose cotransporter in the CCD |
|
|
What regulates aldosterone secretion?
|
Renin-angiotensin (AG) system
|
|
|
Describe the renin-angiotensin system.
|
Liver makes angiotensis (AG)
Renin convert AG --> AG I ACE converts AG I --> AGII AG II stimulates aldosterone secretion by the adrenal gland |
|
|
What increases aldosterone secretion?
|
K+
ACTH |
|
|
What does ANP do?
|
Decreases secretion of aldosterone from the adrenal gland
|
|
|
When does the TAL become the distal tubule?
|
When the tubule touches the originating glomerulus
At this point, the cell become tall and thin: Macula densa (transmits signals to the juxtaglomerula cells) |
|
|
What do the macular densa cells do?
|
"taste" the fluid. if Na concentration is low: means the glomerular lood flow is low and informs the arteriole to releases renin
|
|
|
Which cells actually secrete renin?
|
Jusxtaglomerular cells
|
|
|
What do the juxtaglomerular cells respond to?
|
Tension of afferent fibres
Sympathetic activity Signals from the macula densa |
|
|
How does the extracellular fluid volume regulate renin secretion? (What does the initial changein volume do before the renin system?)
|
Dec plasma volume (causes 3 things):
1) Inc of activity in the renal sympathetic nerve 2) Decrease in arterial P (direct effect on tone of afferent fibers or less stretch) 3) Dec in GFR, causes dec in flow to macula densa, which dec NaCl deivery to macula densa |
|
|
What do these 3 things do to the renin system?
|
In the renal juxtaglomerular cells:
Inc Renin secretion Inc Plasma renin Inc plasma AG II Adrenal cortex: Inc aldosterone secretion Inc plasma aldosterone CCD/DCT: Inc Na reabsorption .: DEC overall secretion of Na |
|
|
Is water reabsorption a direct effect of aldosterone?
|
NO
|
|
|
What is ANP?
|
Atrial natriuretic peptide
Peptide H secreted by cardiac atrail cells when they're stretched |
|
|
When is ANPO secreted?
|
In a High Volume state
|
|
|
What does ANP do? How?
|
Inhibit sodium reabsorption by acting on the tubules
->INC GFR (opposite effect of aldosterone) |
|
|
How does BP affect Na excretioln?
|
BP Increases Na excretion
|
|
|
Describe the action of ANP.
|
Inc in plasma volume
->Cardiac atria: Inc distension -> Inc ANP secretion ->inc plasma ANP (which can dec plasma aldosterone) Kidneys: -> Tubules: dec Na+ reabsorption ->Arterioles: afferent dialation, efferent constriction: Inc GFR End result: Inc sodium secretion |
