Urinary Physiology Flashcards
What makes up a renal corpuscle?
Glomerulus and Bowman’s capsule
What are the 3 layers of the glomerulus?
Fenestrated capillaries
Glomerular basement membrane
Podocytes
What connects podocytes?
Nephrin proteins
What lies between podocytes?
Slit pores
What are mesangial cells?
Phagocyte macromolecules that make it through the basement membrane
What is GFR?
How much blood the kidney filters each miniute
What is normal GFR?
125ml/min
What happens to GFR in increased afferent arteriole resistance?
Decreased GFR
What happens to GFR in increased efferent arteriole resistance?
Increased GFR
What starling force favours filtration?
Hydrostatic pressure
What starling force favours reabsorption?
Oncotic pressure
Which starling force dominates in the glomerular capillaries?
Hydrostatic pressure
Which starling force dominates in the peritubular capillaries?
Oncotic pressure
What is reabsorbed at the proximal tubule?
Sodium
Glucose
Water
Chloride
Old HCO3-
What is the process of Na+ reabsorption?
Na+- K+ ATPase creates the conc. gradient
This drives the SGLT symporter
This also drives the Na+-H+ antiporter
What is the process of old HCO3- reabsorption?
Na+- H+ antiporter uses H+ from carbonic acid and the HCO3- leaves via Na+- HCO3- symporter
What is reabsorbed at the descending limb of the loop of henle?
Water via aquaporin channels
What is reabsorbed at the ascending limb of the loop of henle?
Na+ and Cl- via NKCL2 transporter
No aquaporin channels
What is the counter current multiplier?
Active transport of sodium in the ascending limb sets up the gradient for movement of water out of the descending limb
This creates a hypotonic solution in the DCT and a hyperosmotic environment in the interstitial medulla
What ions are absorbed in the early DCT?
Na+
Cl-
Ca2+
Mg2+
Is water absorbed in the DCT?
No it is impermeable to water like the ascending limb
What are the 2 types of cells in the distal DCT?
Principal cells
Intercalated cells
What is the function of principal cells?
Uptake of Na+
Secretion of K+
What is the function of intercalated cells?
Acid base control- reabsorption of new HCO3-
- Phosphate buffers
- Ammonia buffers
What is the process of new HCO3- reabsorption?
H+ pump- active transport of H+ into the tubule lumen
What is another name for ADH?
Vasopressin
Where is ADH secreted from?
Posterior pituitary
What is the action of ADH?
Increases water reabsorption
Where does AHD act in the nephron?
DIstal tubule and collecting ducts
What is the impact of increased plasma volume on ADH release?
Increased volume (hypervolaemia) means decrease osmolality
Osmoreceptors expand
Decreased ADH release
What is the impact of decreased plasma volume on ADH release?
Decreased volume (hypovolaemia) means increased osmolarity
Osmoreceptors contract
Increased ADH release
What is the mechanism of ADH release?
Increased insertion of aquaporin channels in the apical membrane
What is the end product of RAAS?
Angiotensin II
What is the impact of angiotensin II on the arterioles?
Vasoconstriction
What is the impact of angiotensin II on the kidney?
Increased Na+ reabsorption
H2O retention
What is the impact of angiotensin II on the sympathetic nervous system?
Increased NA release
- Vasoconstriction
- Renin release
What is the impact of angiotensin II on the adrenal cortex?
Aldosterone release
- Acts on principal cells of collecting ducts
- Increases Na+ reabsorption and K+ excretion
What 2 organs are involved in acid base balance?
Lungs- control CO2
Kidneys- control HCO3-
How long does respiratory response take?
Minutes
What is the function of the resp. system in acid base balance?
Chemoreceptors detect the high levels of H+ and CO2 in the blood and alter resp. rate accordingly
Where are the resp. chemoreceptors?
Carotid body
Aortic arch
What is respiratory acidosis?
Low pH
High pCO2
Compensation: increase HCO3-
What causes resp. acidosis?
Opiates
Sleep apnoea
Lung disease
What is respiratory alkalosis?
High pH
Low pCO2
Compensation: decrease HCO3-
What causes resp. alkalosis?
Hyperventilation
Altitudes
Aspirin
How long does urinary response take?
Hours
What is the function of the urinary system in acid base balance
Reabsorption of old HCO3- in the PCT
Production of new HCO3- in the DCT
Excretion of H+ ions as H2PO4- (phosphate buffer) or NH4+ (ammonia buffer)
What is metabolic acidosis?
Low pH
Low HCO3-
Compensation: decrease PCO2
What causes metabolic acidosis?
DKA
Lactic acidosis
Diarrhoea
What is metabolic alkalosis?
High pH
High HCO3-
Compensation: increase PCO2
What causes metabolic alkalosis?
Vomiting
Diuretics
Burns
What is involved in micturition?
- Stretch receptors in bladder wall fire
- Parasympathetic neurons fire, sympathetic neurones stop firing
- Inhibition of somatic motor neurones to external sphincter
