Topic 7: Fluid Balance and Renal Failure Flashcards
What is the typical total fluid volume of the intracellular and extracellular fluid volume?
ICF = 25L/ 40% weight
ECF = 15L / 20% weight
- IF = 12L / 80% ECF
- Plasma = 3L / 20% ECF
How does ADH regulate water balance?
Anti-Diuretic Hormone
Increased osmolarity + Na+ in plasma stimulates osmoreceptors in hypothalamus; releasing ADH and targets kidney ducts. This increases water reabsorption and decreases osmolarity.
Decreased plasma volume + BP inhibit baroreceptors in atrium which also stimulate ADH
How does Angiotensin regulate water balance?
Stimulated by increased ECF and decreased plasma (causes dry mouth) which increased angiotensin II, and the stimulates hypothalamic thirst center. Water absorbs into GI tract and ECF onsmolaity decreased and plasma volume increases
What are the 4 hormones which regulate water balance?
ADH
Angiotensin
Aldosterone
ANP
How does ANP regulate water balance?
Atrial Natiuretic Peptide
Stimulated by increased blood volume and atrial strech, releasing ANP. Effects hypothalamus inhibiting vasopressin; the kidneys increase GFR and decrease renin; adrenal cortex inhibits aldosterone and BP. Leads to increased NaCl and H20 excretion
Whats the difference between ADH, angiotension, aldosterone vs ANP
ADH, angiotensin and aldosterone all increase water absorption to prevent dehydration
ANP causes water excretion
Link water/ electrolyte balance to resitng BP
Increased water, increases BP and dehydration decreases blood pressure. ADH, angiotensin & aldosterone use osmoreceptors to detect water levels in body and activate neurosecretary cells in hypothalamus to icnrease blood solutes. Vasopressin travel sot pituitary gland. ADH acts in kindyes increasing permiability of distal tubules; increasing absorption.
What happens when youre thirsty?
Increased water intake and reabsorption decreases the concentratin of solutes in blood; causing negative feedback and stops ADH production
What are 3 disorders of water balance hypovolaemia (dehydration)
isotonic
hypertonic
hypotonic
Define isotonic
no change in ICF volume, caused by vomiting, diarrhoea
loss of water with preserved normal effective osmolarity of body fluids
Define hypertonic
decrease in ECF & ICF volume, caused by low fuilds, DM,
Imbalance of water and salt - high salt due to water loss
Define hypotonic
decrease in ECF and increase in ICF volume
Caused by low salt, vomiting, addisons disease
Loss of electrolytes
Define hypervolaemia (hyperdyration)
the body holds onto water. sodium concentration in blood is abnormally low
Caused by renal or heart failure
Signs: oedema, increased skin turgor
Define edema:
swelling causes by excess fluid in body tissues
Decreased movement of water into the lymphatic vessels
Summarise the regulation of sodium concentration by the kidneys: renal PROCESS for sodium?
when blood volume or sodium concentration become too high, sensors in heart, blood vessels and kidneys detect the increase, which the kidneys increase sodium excretion returing blood volume to normal
How many mmoles are in ECF, reabsorbed and filterd, and urine by kidneys each day
ECF 2450 mmole
Reabsorbed 25,400 mmole/day
Filtered 25,500 mmole/day
Urine 100 mmole/day
Summarise the regulation of sodium concentration by kidneys: renal REGULATION of sodium?
65% of sodium in filtration is reabsorbed in the proximal tubules. 25% is reclained in loop of Henle, 10% is dependant on aldosterone release in combination of secreted potassium
Water follows sodium if tubule permeability has been increased with ADH
******* Increased K or decreased Na+ concentration in blood plasma and Renin-angiotension mechanism - stimulate Adrenal cortex - releases Aldosterone - targets Kidney tubule - effects Increased NA reabsorption and K secretion - restores Homeostatic plasma levels of NA and K
What is the renal process for Potassium?
K balance = excretion of the amount of potassium in urine equal to that ingested minus amount lost in faeces, sweat.
K is freely filtratable at the glomerulus and undergoes both reabsorption and secretion, the latter occuring at the collecting ducts
When body K is increased, aldosterone secretion is stimulated and this stimulates K excretion
What is the renal regulation of potassium?
K dominates ICF
K is freely filtratable at the glomerulus, and undergoes reabsorption and secretion
Regulation is through aldosterone at the DCT and CD in combination with NA
Vital to maintain accurate K levels in plasma - low/high leads to effects on excitable tissues (heart, muscles)
Summarise the regulation of Calcium in kidneys
Hypocalcemia stimulates parathyroid glands to release PTH
Goes into the blood streamand kidneys. Kidneys PTH activate osteoclastics and calcium and bicarbonate released into blood. PTH increases calcium reabsorption in kidney tubules, PTH promotes kidneys activation of vitamin D, which increases calcium absoprtion from food
Rising calcium in blood inbits PTH release
What is not supposed to be in urine?
Glucose - glycosuria
Proteins - proteinuria
Ketone bodies - ketonuria
Hemoglobin - hemoglobinuria
What solutes are found in urine tests?
95% water, 5% solutes
Nitrogenous wastes: urea, uric acid, creatine
Normal solutes: Na, K, PO4, Ca, Mg, HCO3
What does BUN stand for?
Blood Urea Nitrogen
What is GFR?
Glomerular Filration
Where substances in blood plasma pass from glomerulus into Bowans Capsule, after passing afferent arteriole about 20% of the plasma flowing through glomeruli is filtered
