Di Sole 2

Question 1

Kidneys function on conserving water

Answer 1

• the ability of the kidney to form URINE that is MORE CONCentrated than the plasma is essential for survival
• REQUIRESMENTS for forming conc urin is:
  
  • HIGH OSMOLARITY of the renal medullary interstitial fluid
  • HIGH level of antidiuretic hormone (ADH) also called vasopressin

Question 2

Counter multiplier system

Answer 2

• produces a hyperosmotic renal medulla facilitating the concentration of urine
• vasa recta serve as COUNTER CURRENT EXCHANGERS minimizing washout of solutes from the interstitium
• U-saped structure of the vessels minimizes loss of solute from the interstitium

Question 3

ADH hormone

Answer 3

• AN increase in fluid osmolality, plasma sodium conc caused osmoreceptor cells to shink
• shrinkage of the osmoreceptor cells signals the supraoptic nuclei that release ADH
• in the kidney, ADH controls the degree of dilution or conc of the urine

Question 4

ADH feedback mech

Answer 4

• regulation of extracellular fluid osmolarity in response to water defiict
• Water is conserved in the body, while sodium and other solutes continue to be excreted in the urine
• Opposite sequence occurs when extracellular fluid become too dilute (hypo-osmotic)
• with EXCESS OF WATER ingestion and decrease in extracellular osmolarity, less ADH is formed, the renal tubules decrease thier permeability, LESS WATER IS RE-ABSORBED and large volume of urine is formed.

Question 5

Role of thirst in controlling extracellular fluid Osmolarity

Answer 5

• Fluid intake is regulated by thirst mech
• the hypothalamus contains THIRST OSMORECEPTORS taht sense ECF osmolarity
• These cells stimulate other HYPOTHALAMIC NEURONS CAUSING THIRST and INCREASED water intake in response to hyposomolality

Question 6

stimuli for thirst

Answer 6

• large decrease in circualting blood volume and or blood pressure
• hemorrhage
• dryness of the mouth and throat
• thirst mech and temporarily suppressed after drinking water
  
  • if insufficient water was drunk the persone become thirsty again until the ECG osmolarity is returned to normal

Question 7

Renal AUTO-REGULATION

Answer 7

• Kidney regulateds fluid and electrolytes (sodium chloride) homeostasis by MODULATING the RAPPORT BETWEEN GLOMERULI AND TUBULES
  
  • tubules repsone to glomeruli with Glomerulotubular balance (GTB)
  • Glomeruli response to tubules through the tubuloglomerular feedback (TGF)
• GTB and TGF are FEEDBACK SYSTEMS TO STABILIZE:
  
  • single nephrone GFR
  • distal fluid and electrolytes delivery

Question 8

Glomerulotubular balance function

Answer 8

• GTB enables the function of tubules to COMPENSATE AUTOMATICALLY FOR THE FLUCTUATIONS in FILTRATION RATE in the lomerulus to which it is attached
• GTB is avheived by tubules via:
  
  • changes in hydrostatic and colloid osmotic forces
  • luminal factors

Question 9

Tubularglomerular feedback (TGF) function

Answer 9

• Flucutation in sodium chloride delivery to the distal tubule sensed via the JUXTAGLOMERULAR APPARATUS controls GFR by a feedback mech acting on renal arteriolar resistance
• justaglomerular complex consists of:
  
  • macular densa and justaglomerular cells

Question 10

Angiotensin II

Answer 10

• POWERFUL SODIUM-RETAINING HORMONE
  
  • increases sodium and water RE-ABSORBITON and helps to return blood pressure and Extracellular fluid volume ot normal by three main effects
    
    • CONSTRICTS efferent arterioles
    • STIMULATES ALDOSTERONE secretion
    • Stimulates sodium tubular re-absorption
• REGULATED by chagnes in blood pressure and extracellular fluid volume

Question 11

Aldosterone

Answer 11

• Secreted by ZONA GLOMERULOSA CELLS of the adrenal cortex
• Acts on cells of the CORTICAL COLLECTING TUBULE to INCREASE Na+ re-absorption and K+ secretion
  
  • impaired aldosterone secretion ass with defects in regulation of Na+ and K+ conc
    
    • adrenal destruction or malfunction (addisons disease); adrenal tumors (conn’s syndrome)
• Na+ and K+ intake affect the level of aldosterone
  
  • HIGH Na+ intake DECREASES while HIGH K+ intake INCREASES plasma aldosterone

Question 12

atrial natriuretic peptide

Answer 12

• atrial natriuretic peptide is secreted by cardiac atria cells in volume expansion conditions
  
  • increased level of atrial natriuretic peptide INHIBITS RE-ABSORPTION of sodium and water by RENAL TUBULES, especially by the collecting ducts
  • DECREASED SODIUM and water re-Absorption icnreases urinary excretion and helps the blood volume to return to normal

Question 13

nervous control of kidney

Answer 13

• Increase in activity of renal sympathetic nerves RESULTS in an INCREASE of sodium and water re-absorption due to:
  
  • reduction in GFR by constriciton of renal arterioles
  • increase in tubular sodium re-absorption
  • increase in renin release and angiotension II formation, which further stimulates tubular sodium re-absorption