Final Exam Flashcards
What are the functions of the urinary system?
- Removal of salt, nitrogenous and foreign substances
- Maintain blood osmolarity (NaCl and water)
- Maintain electrolyte balance
- Regulation of blood pH
- RBC production
- Helps control BP
- Helps increase Ca2+
What are the types of filtration in the urinary system?
- Glomerular
- Tubular reabsorption
- Tubular secretion
Glomerular filtration =
(GBP - COP) - (PPOP + CHP)
(out) - (in)
GBP is
glomerular pressure
OUTWARD force
COP is
capsular osmotic pressure
OUTWARD FORCE (but usually 0)
PPOP is
plasma protein osmotic pressure
INWARD FORCE
CHP is
capsular hydrostatic pressure
INWARD force
glomerular filtration rate is defined as
the rate at which filtrate enters the tubule
What role do the kidneys play in regulating the GFR?
- They regulate blood volume
- If BP is too high, GFR is increased resulting in fluid loss
- If BP is too low, GFR is decreased resulting in fluid retention
What happens to the bodies fluid balance if the GFR is increased?
The body has more time to filter and thus loses more fluid causing BP to drop.
What happens to the bodies fluid balance if the GFR is decreased?
The body has less time to filter and thus retains fluid causing BP to increase.
If BP is too high, what happens to the GFR and by what mechanism does this occur?
- Afferent arteriole is vasodilated
- Efferent arteriole is vasoconstricted
- GBP increases
- GFR increases
- Result = fluid loss and BP drop
What factors cause vasodilation of the afferent arteriole?
- ANP - atrial natriuretic protein from the rt atrium
- Inhibition of the sympathetic NS by cardiovascular baroreceptors
- Norepinephrine reduction/ non-release
If BP is too low, what happens in the body to correct?
- Afferent arteriole is vasoconstricted
- Efferent arteriole is dilated
- GBP decreases
- GFR decreases
- Result = Fluid retention + Inc. BP
What factors cause vasoconstriction of AA?
- sympathetic NS releases NE on alpha-1 receptors
How does a JGA respond to a high GFR?
- High GFR causes increased pressure in the MD cells of the DCT
- Increased BP in the MD signals the JG cells
- JG cells cause the afferent arteriole to vasoconstrict
- Vasoconstriction of AA
- Result: Decreased GFR, Decreased BP, fluid levels decrease to baseline
How does a JGA respond to a low GFR?
- Low BP or increased solute sensed by MD cells
- MD cells signal JG cells
- JG cells cause vasodilation of AA
- Result: GFR increases, BP increases, fluid levels rise to baseline
The juxtaglomerular apparatus
- is part of the renal sympathetic nervous system
- is made up of
- the distal tubule (MD cells)
- afferent arteriole (JG cellls)
What is reabsorbed in the PCT?
- 70% of NaCl
- 70% of H2O
- obligatory
- No ADH needed
- All glucose
- 99% amino acids
- 50% Ca2+
What is secreted by the PCT?
- H+ in the form of NH3/NH4 and titratable acid
- causes regeneration of HCO3- in blood
What is absorbed by the descending loop of Henle?
- 5% of H2O
- epithelium freely permeable to H2O
- NaCl is concentrated in a gradient
What are the functions of the ascending limb of the loop of Henle?
- Thin segment
- NaCl diffuses out into interstitial fluid
- Tubular fluid is hypotonic
- Thick segment
- Cl- is pumped out of the tubule
- Na+ follows passively
- filtrate becomes even more dilute
- NaCl is flowing out due to osmotic gradient set up by DLH
- countercurrent multiplication
What is the action of the DCT?
- Site of aldosterone and ADH action
- Reabsorption
- 9% Na (via Na+/K+ pump)
- HCO3- (active transport)
- 50% Ca exchanged for PO43-
- 25% H2O
- Secretion
- K+, H+, PO43-
What is the action of the collecting tube?
- Reaborption
- remaining H20 to concentrate urine
- in outer medulla - by NaCl gradient
- in inner medulla - by urea gradient
- filtrate passed to renal pelvis and out ureters to become urine
- remaining H20 to concentrate urine
To calculate renal clearance of plasma (plasma clearance)
Clearance of x = Rate of urinary excretion of x (mg/min)
plasma concentration of x (mg/mL)
define diuresis
an increased urine flow rate
Define diuretic
an agent that increases urine output
What are the types of diuretics?
- afferent arteriole dilators
- osmotic diuretics
- metabolic inhibitors
What effects do arteriole dilators have on the body?
- They increase hydrostatic blood pressure
- Increased GFR
- increase filtration rate
- increase fluid loss
- decrease blood volume
- decrease blood pressure
What are osmotic diuretics?
- It is a substance excreted in urine that interferes with water reabsorption by osmotically holding water in the tubule
- They also increase salt excretion which decreases water reabsorption
Common osmotic diuretics are
- Mannitol
- glucose
- DM - increased glucose is filtered and remains in the tubes causing polyurea
- urea
- produced by liver
- enters interstitial of medulla
- pulls water out of collecting duct
- urea in tube increases NaCl excretion holding water.
Common metabolic inhibitor diuretics are
- loop diuretics
- inhibit Na+ reabsorption
- Act at the thin ALH
- Na+ stays in tubule and is lost,, water follows
Increased solutes results in ________ osmolarity
increased
direct relationship
Increased fluids results in ______ osmolarity
decreases osmolarity
indirect relationship
Aldosterone release from the z. glomerulosa causes
- Na+ reabsorption in exchange for K+
- Na+ absorption can occur on alone
- water will follow ONLY if ADH is present
Aldosterone release may be stimulated by
increased angiotensin II through the RAAS system
High K+ levels
Atrial Natriuretic Peptide (ANP) causes what effect in the body
- Inhibits Na+ reabsorption in the DCT
- Inhibits ADN release blocking reabsorption in the DCT
- Causes vasodilation of the AA
- thus increasing GFR
Estrogen has a similar effect as
aldosterone
increases Na+ absorption (bloating)
Countercurrent exchange occurs in what regions
descending loop of henle
ascending vasa recta
the solute in the renal cortex is
salt
the solute in the renal medulla is
urea
normal blood osmolarity is
285-300 mosm/L
Increased osmolarity causes
shrinking cells and depolarization
ADH causes increased water absorption in the
DCT and collecting duct
diabetes insipidus is
lack of ADH, water loss without sugar
excess water loss, patient is always thirsty
Maltase digests
the disaccharide maltose into
glucose + glucose
Lactase digests
disaccharide lactose into
glucose + galactose
Lipase digests
fats/ triglycerides
carboxypeptidase digests
proteins
other protein enzymes are trypsin, chymotrypsin (s. int) and pepsin (stomach)
The SI absorbes
- most nutrients and 8500 ml of water
- Duodenum: some sugars
- Jejunum: sugars, amino acids, dipeptides, fat components
- Ileum: vitamin B12 and bile salts
The LI absorbs
- 400 mL
- vitamin B and K
receptive relaxation occurs in the
stomach in response to each swallow to allow the food bolus to enter and prevent esophageal reflux
gastrin is
a peptide hormone that stimulates secretion of gastric acid by the parietal cells of the stomach and aids in gastric motility.
pepsinogen is
a substance excreted by chief cells in the stomach that is converted into the enzyme pepsin by gastric acids (HCl)
autocrine control of endocrine system is
- hormone binds to same cell that released it
peracrine control on the endocrine system is
- where the hormone binds to receptors on adjacent cells
endocrine control of the endocrine system is
where the hormone is transported through a vein or duct before acting on a cell/organ/system etc.
