Salt and water balance Flashcards
(57 cards)
How much body sodium exchangeable?
Where located
Where rest?
Exchangeable- 70%
Bone crystal- 30%
ECF- 50% body sodium
Draw fluid 70kg man?
Ions
IF- K+
ECF- Na+
Main ion IF?
Main ion ECF?
IF- K+
ECF- Na+
Define:
Osmolality
Osmolarity
Oncotic pressure
Osmosis
Osmolality – concentration of solution expressed as solute particles per kg (OPPOSITE)
Osmolarity – concentration of solution expressed as solute particles per L (OPPOSITE)
Oncotic pressure – pressure exerted by plasma protein on capillary wall
Osmosis – process by which molecules within a solvent pass through a semi-permeable membrane. High conc. To low conc.
Where are osmoreceptors located?
Hypothalamus
Function osmoreceptors?
Detect low water potential
What occurs when osmoreceptors detect low water potential?
1) Osmoreceptors in hypothalamus detect low water potential
2) Loss water reduces osmoreceptors volume
3) Trigger stimulation nerve cells in hypothalamus
4) Trigger ADH to be released from posterior pituitary
5) Act kidneys
What stimulates posterior pituitary to release ADH?
Hypothalamus
AP travel down- cause release ADH into blood stream
Act kidneys
Where is urine diluted?
Where is urine concentrated?
Diluted- LOH
Concentrated- distal tubules and collecting ducts
What is descending loop in LOH permeable and impermeable to?
What is ascending loop in LOH permeable and impermeable to?
Descending- Permeable- water
- Impermeable- NaCl
Ascending- Permeable- NaCl
- Impermeable- water
What occurs in thin descending limb?
Highly permeable water- reabsorption- AQP1 channels
What occurs in thin ascending limb?
Na reabsorption- Na+ channels
Cl- reabsorption- Cl- channels
What occurs in thick ascending limb?
Primary site sodium reabsorption
Impermeable water
Na+/K+ ATPase on the basolateral membrane
Pump Na+ and K+ into cell
Create low intracellular concentration of sodium
Inside of cell becomes negatively charged- creating an electrochemical gradient
Sodium moves into cell (from the tubular lumen) down the electrical and chemical gradient, through the NKCC2 transporter on the apical membrane
How are potassium ions transported back into tubule?
Renal outer medullary potassium (ROMK) channels
On apical membrane- prevent toxic build up
Explain counter current multiplication system?
Thick ascending limb impermeable water
Interstitium concentrated ions- increase osmolarity
Drive water reabsorption from descending limb- water moves areas low osmolarity to areas high osmolarity
Where does LOH descend?
Medulla
Where is glomerulus?
Cortex
https://www.youtube.com/watch?v=Vqce2dtg45U
https://www.youtube.com/watch?v=Vqce2dtg45U
What occurs ascending limb?
Active transport ions out
Allow passive diffusion water in descending into interstitium
What occurs ascending limb?
Active transport ions out
Allow passive diffusion water in descending into interstitium
Explain RAAS system?
1) Reduced sodium delivery to distal convoluted tubule detected by macula densa cells
2) Reduced blood pressure (decrease perfusion pressure) detected by baroreceptors in afferent arteriole
3) Sympathetic stimulation juxtaglomerular cells via B1 adrenoreceptors
4) Renin cleaves angiotensinogen (liver) to form angiotensin 1
5) Angiotensin 1 converted to angiotensin 2 by angiotensin converting enzyme (ACE- lungs)
6) Angiotensin exert action binding receptors (most AT1)
7) Effect angiotensin:
Arterioles- vasoconstriction
Kidney- stimulate Na+ reabsorption
Adrenal cortex- release aldosterone
Hypothalamus- increase thirst sensation
- stimulate release ADH- AQP1
8) Angiotensin 2 act AT1 receptors in endothelium of arterioles- vasoconstrict- signalling via Gq protein- increase peripheral resistance- increase blood pressure
9) Angiotensin 2 act hypothalamus stimulate thirst- fluid consumption- raise circulating volume- raise bp
Act hypothalamus increase secretion ADH from posterior pituitary- more concentration urine
10) Angiotensin 2 stimulate sympathetic nervous system- increase release noradrenaline- increase CO, vasoconstrict arterioles, release renin
11) Angiotensin 2 act kidney:
1) Renal artery and afferent arteriole-
- Vasoconstriction- increase resistance (less efferent)
- Voltage-gated calcium channels open- influx of calcium ions
2) Efferent arteriole- increase resistance
-Vasoconstriction (greater than afferent arteriole)
3) Mesangial cells- contraction, l
- Decreased filtration area
- Activation of Gq receptors- open voltage-gated calcium
channels
4) Proximal convoluted tubule- Increased Na+ reabsorption
- Increased Na+/H+ antiporter activity
12) Act adrenal cortex stimulate release aldosterone (released
zona glomerulus)
Aldosterone act principal cells of collecting ducts in nephron-
expression apical epithelial Na+ channels (ENaC) to reabsorb urinary sodium- sodium pumped into blood via Na/K pump- K+ moved blood to principle cell- renal tubule- K+ excreted
Aldosterone reduces lvls potassium blood
Activity of the basolateral Na+/K+/ATPase is increased
What inhibits release renin? What stimulates release?
Atrial natriuretic peptide (ANP)
Released by stretched atria in response to increase bp
Draw RAAS?
