2. Physiology Flashcards
How do the kidneys control secretion of substances?
Through glomerular filtration. This relies on the balance of hydrostatic and oncotic forces.
What determines a molecules ability to be filtered?
Molecular size
Electrical charge
shape
Describe the active barriers of the glomerulus that prevents filtration of substances
Fenestrations- pores in endothelial cells. Stop RBC
Basal lamina- prevents large proteins
Slit membrane- prevents medium proteins
What physiological factors affect kidney filtration?
Sympatheric nerves
Circulating catecholamines
Angiotensin II
At what blood pressure does renal filtration start to deteriorate
When MAP<60
How much excess blood can be taken per minute to perfuse other organs during oxygen requiring circumstances
800mls/minute
if this occurs for too long then circumstances such as AKI occur
How do the kidneys deal with glucose?
reabsorb up to 10mmol per day
How does aldosteerone affect potassium?
Aldosterone is released in response to increased potassium levels. It works to decrease potassium`
How are lipid soluble drugs excreted if the kidneys manipulate charge and water
The liver turns them into polar compounds
What is ADH?
What controls its release?
Anti-diuretic hormone- preserves water levels. It does this by creating water channels in the collecting ducts
H20 shrinks out of cells
Low ECF volumes
Others (pain,emotion alcohol)
What is the function of aldosterone?
Alters sodium in the distal tubule. Acts to prevent water loss and raise blood pressure
What is the function of renin?
What produces renin?
To create angiotensin
It is the rate limiting step for this pathway as its produced by the juxtaglomerular cells (macula densa)
Why are the juxtaglomerular cells described as the renal baroreceptors?
They respond to the decreased pressure in the kidneys
They release renin and are inversely proportional to the rate of delivery of NaCl
There is a negative feedback from angiotensin II and ADH.
What is considered more important volume losses or osmolarity losses?
Volume losses considered more important. This is because perfusion to the brain is prioritised.
How does aldosterone affect sodium and potassium?
Aldosterone increases sodium reabsorption and decreases potassium as a result.
