salt balance Flashcards
what makes up the juxtaglomerular apparatus?
juxtaglomerular cells, macular densa, lacis cells (agranular cells)
What is the function of macula densa cells?
sense changes in NaCl in the thick ascending limb.
Where is the macula densa?
at the transition between the thick ascending limb and the distal convoluted tubule
What do macula densa cells do in response to a low NaCl level?
dilation of renal afferent arteriole, release prostaglandins to trigger juxtaglomerular cells to release renin
What do juxtaglomerular cells produce?
The enzyme renin
What are the three ways of activating renin release from the JG cells?
- sympathetic stimulation in response to low BP detection by baroreceptors.
- decrease in wall tension and vasoconstriction
- decrease in NaCl delivery to the macula densa cells- mediated by prostaglandins.
Where is aldosterone released from?
The zona glomerulosa of the adrenal cortex
What is the normal osmolarity value entering the proximal convoluted tubule?
285
When would ANP be secreted?
In response to high blood volume
Where is ANP released from?
cardiac atrial cells
What is the function of ANP?
cause sodium loss, decrease circulating volume
What is Nedd4-2?
An enzyme that ubiquitinates ENac in order to endocytose and degrade the channel
What is the function of SGK1?
inactivate Nedd4-2 by phosphorylation
What is Liddle’s syndrome?
Mutation in ENac so that it cannot be ubiquitinated. ENac stays in the membrane, continuous NA+ uptake, very high circulating volume ( high BP)
What happens if the function of ENac is blocked?
Na+ not retained, decreased circulating volume
