Urinary Part 2 Flashcards
What is tubular reabsorption? Give examples. Is it active or passive?
Returning important substances from filtrate back into the blood
AAs, water, glucose, vitamins
Both
Where does tubular reabsorption occur?
PCT microvilli
Sodium is actively transported out of the filtrate into ISF by which enzyme?
Na/K ATPase
Describe the proportionality of the following..
Glucose filtration
Glucose reabsorption
Glucose secretion
Directly proportional. High levels - glucosuria
Proportional until saturation. Rest of glucose - glucosuria?
Secretion, zero until point, then proportional
Where is the majority of HCO3 reabsorbed? Does it have a transporter protein? How is it reabsorbed?
PCT
No
Na/H antiport
Write the equation between H2O and CO2
H2O + CO2 = H2CO3 = H+ + HCO3-
Most proteins are too large to enter the bowmans capsule. What happens to the small proteins that enter?
Endocytosis in PCT
Degradation into AAs
Absorbed into capillaries
Why is sodium crucial for reabsorption?
Filtrate has same concentration as plasma (PCT)
How is water reabsorbed? What is this after? What does this also fuel?
osmosis
After removal of Na/Cl
Fuels secondary AT of glucose
What are the 2 routes of absorption into ISF?
Paracellular - passive, adjacent tubules via gap junctions
Transcellular - between cells
What proteins are found in the membrane of the descending LOH?
Aquaporins - water diffuses into blood, gets concentrated the further down
What transporters are present in the ascending loop of Henle?
Na/K/ATPase
No aquaporins
Dilutes as ascends
The vasa recta countercurrent system is not enough to create an osmotic gradient. Why is this?What helps this?
Nephrons so closely packed
Urea recycling
What is the vasa recta?
Capillary network in juxtamedullary nephrons
Supplies oxygen and nutrients to the medulla
Describe the filtration and reabsorption of urea
Small - filtered
Not actively reabsorbed
50% passively reabsorbed
What creates urea recycling? How do these allow urea movement?
Medullary collecting duct
Descending vasa recta
LOH
Have protein permeable to urea, allows it to move down the concentration gradient
Where is antidiuretic hormone produced and stored?
Hypothalamus
Posterior pituitary
How does antidiuretic hormone concentrate urine?
Increases number of aquaporins in nephron
What does the ability to concentrate urine depend on?
Loop of Henle length, aquaporins
Number of juxtamedullary neurons
By the DCT, describe the filtration and reabsorption of sodium, potassium and bicarbonate
Na - 100% f, 90%r
K - 100% f, 100% r
HCO3 - 100% f, 100% r
Proteins in the DCT are able to pump H+ against large concentration gradients. What are the 2 types of cell and when do they work?
Type A - during acidosis, increase H+ secretion, absorb HCO3
Type B - during alkalosis, increase HCO3 secretion, absorb H+
What is aldosterone?
Fat soluble hormone
Regulates protein synthesis and ion channels which enable potassium secretion
What is the muscle found in the bladder? What is its innervation?
Detrusor
Parasympathetic - pelvic nerve
Sympathetic - hypogastric nerve.
Does urine composition change between the collecting duct and bladder?
Only in horses
What happens as the bladder fills?
Detrusor relaxes
Continuous excitation of sphincter muscles - acetylcholine on nicotinic receptors.
Where is the external urethral sphincter? Is it voluntary or not?
Peritoneum
Yes
Is the internal urethral sphincter voluntary?
No
What provides the sympathetic nerve supply to the internal sphincter?
Hypogastric
What provides the parasympathetic nerve supply to all of the bladder system? except the detrusor - pelvic nerve
Pudendal
Describe the process of urination
High pressure opens internal sphincter
Neck of bladder dilates
Inhibition of skeletal muscle relaxes external sphincter
How does the brain know when the bladder is full?
Mechanoreceptors, stretch in bladder wall
In newborns, what nerves controls bladder emptying?
Spinal reflex
What is sensible loss? What is insensible loss?
Sensible -water loss via urine
Insensible - water loss via sweat, exhalation
What detects plasma osmolarity? What happens when there is a decrease?
Osmoreceptors in hypothalamus
Fire action potentials, stimulates release of ADH and increases thirst
Why might be there a change in blood pressure/volume?
Haemorrhage
What is responsible for membrane potentials? Is it stored in the body?
Potassium
No
Describe the relative concentrations between urine and ECF concentration of potassium. What is this regulated by? What feedback is this?
Higher k+ in urine than in ECF
Aldosterone
Negative feedback
where is aldosterone released?
Adrenal cortex
What does aldosterone stimulate?
Collecting duct cells
To secrete more K+, which causes reabsorption and Na/Cl and water
Increases blood pressure
What controls changes in sodium absorption?
RAAS system
Natriuretic peptides
Hydrostatic pressure
When is angiotensin 2 released? What does it do?
In response to low blood pressure
Causes vasoconstriction and stimulates aldosterone
Causes hypothalamus to secrete ADH and increase thirst
Homeostatic functions of the kidney prevent fluctuations in what?
Fluid
Acid/base balance
Electrolyte balance
How can aerobic and anaerobic glycolysis help cause acidosis?
Produces H+ and CO2
What are the 3 lines of defence against acidosis/alkalosis
Buffer
Breathing system
Kidneys
How do the buffer systems restore pH? What is a limitation to this?
Bind to H+/OH- until they are excreted
Cannot buffer itself, can’t protect ECF
How can the lungs counteract acidosis/alkalosis? What are the limitations to this?
Expelling CO2
Acidosis - faster RR and depth
Relies on normal respiratory function, limited availability of HCO3
How does the kidney restore pH to normal?
Excretion and reabsorption of ions
A decrease in glomerular filtrate rate can cause kidney dysfunction. What changes would happen to the blood?
Increased urea, creatine, phosphate
Decreases HCO3 = metabolic acidosis
More dilute urine = dehydration
Why does a compromised cardiovascular system affect renal function?
20% of CO goes to kidney
What are the 3 types of problems which can result in azotaemia?
Prerenal - reduced blood supply to kidney e.g. heart problem
Renal - kidney itself
Post renal - blockage of urine flow e.g. kidney stones
For prerenal and renal problems, can urine be concentrated?
Prerenal yes as problem is above kidneys
Renal no, as issue is with the kidneys
Kidney failure can also cause hypokalaemia. What does this cause? What is a symptom?
Less excitable muscle/nerve cells
Floppiness
Kidney failure can also cause hyperkalaemia. What does this cause? What is a symptom of this?
Nerve cells to be hyperpolarised, cannot depolarise
Less excitable
SLow heart heart
What% of the body is solid and water?
40% solid
60% water
What proportion of liquid is ECF/ICF?
2/3 ECF
1/3 ECF
What is ECF made of? And %
80% ISF
20% plasma
What do natriuretic peptides do?
Cause sodium excretion
