kidney 3 Hormonal control mechanisms Flashcards
(27 cards)
What regulates water volume?
2) Rulates plasma Na+?
1) Vasopressin/ Antidiuretic Hormone (ADH)
2) Aldosterone
describe direction of flow in vesa recta?
2) what is its function?
flows in opposite direciton to flow of loop of Henle
2) Stops concentration gradient made by loop of Henle being washed away
results of loop of henle?
water lost but still dilute
what occurs in collecting duct?
collecitng duct H2O permeable, water exits into interstitium = concentrated urine
What produces ADH?
supraoptic and paraventricular nuclei of the hypothalamus
Where is ADH released from?
posterior pituatry gland
What causes releases of ADH?
increased plasma osmolarity (by even 1%) senscended by osmoreceptors in hypothalamus message sent to posterior pituatry
- decreased blood P
- decreased blood vol.
What are the effects f ADH?
increases water permeability of collecting duct
- increases urea permeability in inner meddullary region of collecting duct
- increases NaCl reabsorbtion in TAL
How does ADH act on collecting duct to produce hyperosmotic urine?
ADH binds to receptor on SA on basolateral SA of collecting duct
2) stimulates adenylyl cyclase = cAMP activate protein kinases
3) increases insertion of aquaporins into apical SA of CD
4) increases in water permeability thus there is more water reabsorbtion
WHat does hyperosmotic urine mean?
cocentrated urine
lots of solute
What is the effect of no ADH on collecting duct?
no aquaporins in apical surface thus urine is hyposmotic
What are the effects of osmoreceptors when stimulated in their different locations + where are they ?
1) supraoptic & paraventricular nuclei - stimulate ADH release from posterior pituitary if water deprived , if excess fluid ingested causes ADH release suppression
2) lateral preoptic area- causes feeling of thrist
Osmoreceptors are the main controllers of ADH, what else control them?
atrial natriuretic peptide (atrial stretch, ANP release = inhibits ADH)
nicotine (stimulates ADH)
alcohol (inihibits ADH)
Where is aldosterone released from?
adrenal cortex
aldosterone release is stimulated by
increased K+ - decreased blood pressure (via RAAS) (increased osmolarity inhibits)
1) What are the effects of aldosterone?
2) What is the net effect?
- increases Na+ reabsorption in the distal tubule & CD
- increases K+ secretion in the distal tubule & CD
2) increased blood volume and pressure
What is the site of action of aldosterone?
collecting duct
What effect does aldosterone have on the collecting duct?
1) binds to receptor in cytoplasm
2) initiates transcription
3) increase number of ENaCC channels in apical surface and more Na-K pumps
4) more Na+ uptaken , Cl- also as follows Na+
What are the macula densa cells?
an area of closely packed specialized cells lining the wall of the distal tubule, in loop of henle, sense differences in blood flow and Na+
What happens if there is an decrease in blood flow in afferent arteriole?
(due to hypovolemia of hypotension)
1) arteriole will relax as low blood pressure detected by baroreceptors leading to sympathetic stimulation= fall in tension
2) if this doesn’t increase blood flow enough macula densa cells will recognise low amounts of Na+ passing by and relase paracrine hormone to juxtaglomerular cells
3) stimulating them to release renin
4) influencing the renin-angiotensin pathway?
What is the role of macula densa cells in the renin-angiotensin pathway?
1) macula densa cells detect low Na+
2) send paracrine hormone to juxtagulomerular cells
3) stimulating them to produce reninithat produce
What is the effect of renin on the renin-angiotensin-aldosterone system?
activates andiotensinogen to angiotensin 1, converting enzyme in lung to angiotensin 2
stimulating release of aldosterone by adrenal cortex, increase Na+
Why is release of ANP differenet ot aldosterone and ADH?
released when blood volume increases as atria stretch so release ANP
ANP effects the hypothalamus how?
inhibits release of ADH
