Renal Physiology Flashcards
What is in the ultrafiltrate?
Same components as blood plasma, minus the proteins
What is the role of the cortical nephrons?
Absorption and secretion
What is the role of the juxtamedullary nephrons?
Creating conditions to forma concentrated urine
What occurs in the proximal tubule?
Most of the fluid is reabsorbed as isotonic NaCl, along with vital nutrients (glucose, amino acids)
What is the role of the loop of Henle?
Controlling the concentration of the urine
What is the role of the distal tubule?
Fine tuning of electrolyte conditions
Which structure collects the water/solutes reabsorbed by the nephron?
Vasa recta
What is the role of the juxtaglomerular apparatus?
Specialised hormone-secreting region
What size do molecules have to be to pass the secondary processes of the glomerular capillary?
Anything <3.5nm can easily pass
What are the filtration forces that enable fluid to cross the glomerular capillary wall?
Hydrostatic pressure in the capillary; osmotic forces across the capillary (due to plasma proteins)
Which waste product can be used as a blood-borne biomarker for renal function/GFR?
Creatinine
Is there any concentration of tubular contents in the proximal tubule?
No. Fluid remains isotonic
What is the GFR in a normal young adult?
120ml/min
How is sodium transported across the apical membrane of the PCT?
Co-transport with glucose/amino acids, antiporter with protons
How is sodium transported across the baso-lateral membrane of the PCT?
Na/K/ATPase on baso-lateral membrane
What happens if you put a cell into a hypotonic solution?
Water moves into the cell and it swells/bursts
What happens if you put a cell into a hypertonic solution?
Water moves out of the cell and it crenates
What is normal plasma osmolality?
290molsmol.kg^-1 H2O
Where is ADH secreted from?
Posterior pituitary gland
What is the overall function of ADH?
Increase the number of aquaporins in the collecting duct
What occurs in the descending limb of the LoH?
Water leaves through aquaporins to the hyperosmotic medullary interstitium
What occurs in the ascending limb of the LoH?
Na/K/2Cl- leaves cell via co-transporter to maintain hyperosmotic medullary interstitium
What occurs in the ascending limb of the LoH?
Na+ (and K+/2Cl-) leaves cell via apical co-transporter and basolateral Na+ pump, to maintain hyperosmotic medullary interstitium
What are the high pressure sensors of blood volume?
Arterial baroreceptors in the carotid sinus and aortic arch; juxtaglomerular apparatus of kidney
What are the low pressure sensors of blood volume?
cardiac atria; pulmonary vasculature
Where/why is renin secreted?
Renin secreted from the juxtaglomerular apparatus in response to low renal blood flow/pressure (aids water reabsorption at the distal tubule)
What is the effect of increased circulating aldosterone?
Stimulates transcription of apical Na and K channels
What is the overall effect of atrial natriuretic peptide?
Increased excretion of Na+ (and therefore water) in response to heightened blood pressure
What are the main regulators of K+ secretion?
K+ itself and plasma aldosterone released from adrenal cortex (an increase in either will enhance secretion)
What is the normal value of calcium in plasma?
2.2-2.6mmol/l
What is the biologically active form of vitamin D3 called?
1,25-(OH)2-vitamin D3
Which nerves are active when the bladder relaxes?
Hypogastric (sympathetic) and pudendal (somatic)
Which nerve is active when the bladder contracts?
Pelvic nerve (parasympathetic)
Where in the brain is the decision not to void the bladder made?
Medial pre-frontal cortex - inhibits the pontine micturition centre
