Anything that is soluble in water gets cleared out by the:
Kidney
Insoluble/fatty/viscous stubstances are cleared out by the:
Liver
GFR regulates what
Blood volume
How many litres of fluid are filtered per day in the GFR?
Male: 180L/day
Female: 144L/day
How much litres in the blood of a human?
6L - Therefore needs to reabsorbed a majority of the the filtered fluid to maintain fluid balance
To get rid of more fluid what needs to happen to the GFR
Increase GFR (pressure) so more blood is filtered out to the bladder and excreted as urine - this is done by decreasing sympathetic activity (opens the afferent arteriole more than the efferent) and pressure goes up and more fluid sits in the GFR which gets filtered to the bladder.
What needs to happen when you are dehydrated?
Conserve water by decreasing GFR so fluid doesn’t get filtered but out in the efferent to be circulated back to the body system.
To increase urine output what needs to happen?
increase GFR activity - decrease sympathetic drive: open up the afferent more than the efferent so the pressure difference is greater. More sits in the GFR –> more in the bladder
Where are the macula densa cells and what does it sense?
Located in the distal tubule.
They sense Na+ concentration in the filtrate and regulate BP and GFR by triggering tubuloglomerular feedback and modulating renin release from juxtaglomerular cells.
What is a intrinsic mechanism that regulates GFR?
Tubulo Glomerular Feedback - A negative feedback loops that is triggered by sensing NaCl in the filtrate to regulate GFR and BP
What is an extrinsic mechanism that regulates GFR (external factor occuring outside the GFR)
Sympathetic nervous system
- Decreases sympathetic activity (always in the afferent) which opens more than the efferent. HP increases and more fluid is filtered out to the bladder.
- Increases sympathetic activity which decreases HP in the GF and less fluid is filtered out as urine.
What is filtrated before entering the proximal tubule?
HCO3-, Glucose, Amino acids
At the end of the proximal tubule:
1. How much fluid was reabsorbed from the GFR?
2. Is there change in the Na+ conc.?
3. is it hyper, hypo or isosmotic?
- 80% of GFR is reabsorbed
- No because water is dragged with Na+ and maintians the concentreation
- Iso-osmotic - even though tubular fluid drops from 6L/h –> 1.2L/h, omolarity doesn’t change because urea makes up the missing osmoles
True or False
Urea is not reabsorbed, therefore concentration is high in the urine?
TRUE
What happens to urea in the proximal tubule?
It remains inside the tubule.
Regulates osmolarity inside the tubules (= iso-osmotic)
- Urea conc. ges higher and higher as it moves along the tubule.
In the ascending loop of henle what transporter is on the apical (lumen) side?
Na/Cl/K+ co trasnporter
It uses a concentration gradient to get ions across.
What does the Na/K ATPase channels do?
Gets rid of Na+ inside the tubular cells to the interstital fluid - creates Na+ defficiency
What is the osmolarity at the bottom of the Loop of Henle (medulla)
1200 mOsm/L
x4 than the cortex
Is the ascending limb impermeable or permeable to water?
Impermeable
(So NaCl leaves the cells and water remains inside)
The more concentrated the inner part of the kidney means:
More water is reabsorbed
The more concentrated our urine is makes us liver longer periods without access to water. Why?
As more water gets reabosrbed because osmolarity is very high
Cortical papillary:
Creates a gradient between the cortex and medulla of the kidney.
Stonger cortical papillary means it can reabsorb MORE water.
What are the 7 steps that occur when you’re dehydrated?
- Water deficiency
- Increase in osmolarity in the ECF
- Osmoreceptors senses this and ADH is triggered
- ADH increases in the plasma
- Increase water permeability in distal tubule/collecting ducts
- increease in water reabsorption
- Decrease in water excretion
What senses osmolarity in fluids? How do they sense it?
Osmoreceptors.
They shrink or increase by sensing osmolarity (blood changes) and effectively sends signals to release ADH
(in posterior pituitary)
