The kidney 2 Flashcards
What occurs when isotonic fluid flows down the descending limb?
Becomes more concentrated
What happens when isotonic fluid flows up the ascending limb?
Becomes less concentrated
How can the collecting duct concentrate urine?
When an osmotic gradient has been established between each limb
When can water be reabsorbed?
Osmotic gradient and tubule is permeable to water
When are the tubules permeable to water?
In the presence of vasopressin
Where is vasopressin produced?
Hypothalamus
What is vasopressin?
Hormone that is stored in the posterior pituitary gland and secreted into the blood stream
How is osmolarity of fluid detected?
Osmoreceptors in the hypothalamus
When is vasopressin released, triggering thirst?
Increased osmolarity
When is vasopressin inhibited, suspending thirst?
Decreased osmolarity
Why are collecting tubules in hairpin shapes?
To prevent NaCl and water permeability of capillary walls and avoiding destruction of osmotic gradient
What are the 3 classes of urine?
Normal=isotonic
Over hydration=hypotonic
Dehydration=hypertonic
What controls the exit of urine from the bladder?
Internal and external urethral sphincters
What is Na+ reabsorption controlled by?
Proximal tubule, loop of Henle and distal tubule (hormonal control)
What occurs when sodium load is high?
Extra water is held in extra cellular fluid causes an increase in kidney volume
What occurs when sodium load is low?
Less water is held in extra cellular fluid causing lower kidney volume
What occurs if blood pressure is low?
Kidney cells secrete renin
What is the renin-angiotensin-aldosterone system?
Renin activates plasma protein to angiotensin I which is converted to angiotensin II which stimulates aldosterone secretion
What is the role of aldosterone?
Increases sodium reabsorption
How is salt excreted from the body?
Renin secretion is inhibited and sodium reabsorption stops and salt is excreted through urine
How is potassium excreted?
Through proximal, distal and collecting tubules
What stimulates secretion of potassium?
Aldosterone and acid
How is pH controlled in the body?
Excretion of CO2 via the lungs and excretion of acid via the kidneys
How is H+ generated for the body?
Disassociation of carbonic acid to give free H+
How does the respiratory system reduce pH?
Preventing generation of H+ by removing CO2 and therefore preventing carbonic acid formation
What are the 4 chemical buffering systems?
Bicarbonate system
Protein buffer system
Haemoglobin buffer system
Phosphate buffer system
How is bicarbonate excreted?
Reabsorption of filtered HCO3- to plasma and addition of HCO3- to plasma
How is HCO3- linked to H+ secretion?
As H+ is secreted HCO3- is transferred into plasma
