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.
How does ANP affect sodium and potassium?
ANP overrides aldosterone’s effects
decreases sodium and water
How is ANP released?
The atria are stretched by increased volume leading to sodium and water excretion
Why does diabetes cause increased peeing and thirst?
Glucose gradually disrupts the osmotic balance in the proximal tubule and loop of henle kidneys
This leads to mass loses of isotonic urine and therefore ADH is released to maintain ECF.
What equation controls the acid base balance in the body?
CO2+H20H2CO3H+ + HCO3
What are the producers of acid?
Carbonic acid (produced in ventilation) Metabolic acids
What are the normal ranges of pH, oxygen and carbon dioxide
pH- 7.37-7.43
O2- 12kPa
CO2-5.3kPa
What can the kidneys do to regulate HCO3-
Reabsorb filtered HCO3
Generate new HCO3 (by retaining CO2 and excreting the dissociated hydrogen ions)
What is implemented to excrete large amounts of acid?
Ammonium
it is excreted as ammonia which combines with hydrogen to form ammonium. Ammonia is permeable ammonium is not
This tales 4-5 days to reach peak hydrogen excretion.
What is the simple hack for acid base disorders?
Lungs control CO2
kidneys control HCO3
What are some causes of respiratory acidosis?
Drugs which depress the medullary respiratory centres
Obstruction of airways
Chronic lung disease
What are some causes of respiratory alkalosis?
Voluntary hyperventilation
Aspirin
Altitude
WHat are some causes of metabolic acidosis?
Increase in hydrogen
Failure to excrete a normal dietary load of H+ as in renal failure
Loss of HCO3 as in diarrhoea
What are some causes of metabolic alkalosis?
Hydrogen ion loss (loss of gastric secretions)
Renal hydrogen loss
Excess administration of HCO3
Massive blood transfusion
