Salt and water balance Flashcards
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?
What releases renin?
Granular cells of the renal juxtaglomerular apparatus
What stimulates release renin?
1) Macula densa detect reduced sodium delivery to distal convoluted tubule
2) Baroreceptors- reduced BP/perfusion pressure in the afferent arteriole of kidney
3) Sympathetic stimulation of the JGA via β1 adrenoreceptors
What is release renin inhibited by? What releases it?
Atrial natriuretic peptide (ANP)
Stretched atria- response increase BP
What produces angiotensin?
Liver
Function angiotensin?
Cleave renin to form angiotensin 1
What converts angiotensin 1 to angiotensin 2?
Angiotensin converting enzyme
Where is AACE produced?
Lungs
What does angiotensin bind to?
G protein coupled recepetors
AT1 and AT2
Effect angiotensin? (5)
1) Vasoconstrict arterioles- Gq coupling- increase resistance and bp
2) Act hypothalamus- thirst
- increase ADH- AqP2
3) Stimulate sympathetic NS increase release noradrenaline
- increase CO, vasoconstriction arterioles, release renin
4) Renal effect
Vasoconstriction
Afferent and efferent ( E more)
Mesangial cells- contraction- decrease filtering area
Proximal convoluted- increase Na+
5) Act adrenal cortex stimulate release aldosterone
Sodium reabsorption- water moves
What effect ADH?
Increase transcription an idnsertion AQP2 channels to apical membrane of DCT and CD
Water move out- increase blood volume
Where is ADH synthesised?
Where stored?
Synthesis- hypothalamus
Stored- posterior pituitary
What inhibits ADH?
ANP
What regulates release ADH?
Osmoreceptors- lack BBB- detect osmolality blood
Fall blood plasma what occurs? (ADH)
Increase plasma sodium conc
Osmolarity increase
Water exit cells- osmoreceptors contract
Afferent signals sent from hypothalamus to posterior pituitary- increase release ADH
What detects changes blood volume? Where located (2)
Baroreceptors
Carotid artery
Aortic arch
What occurs baroreceptors detect reduction blood pressure?
Relay vagus nerve
Send afferent signals- stimulate release ADH from posterior pituitary
What occurs baroreceptors detect reduction blood pressure?
Relay vagus nerve
Send afferent signals- stimulate release ADH from posterior pituitary
What type of steroid hormone is aldosterone?
Mineralcorticoid
Where is aldosterone release?
Zona glomerulosa of adrenal cortex
Effect aldosterone (what cell act on)?
Act principal cells collecting duct in nephron
Increase expression apical epithelial Na+ channels (ENaC)
- reabsorb sodium
Increase activity basolateral Na+ K ATPase pump
Does aldosterone cause increase or decrease potassium lvls in blood?
Decrease
Cause increase expression of apical epithelial Na+ channels (ENAC)- absorb sodium
Pump sodium into blood via sodium/potassium pump
Potassium moved from blood into principle cell
Exit into renal tubule
Excreted urine
Draw RAAS?
What inhibits renin? (2)
Angiotensin 2 production
ADH production
What produces albumin?
Liver
What is main protein involved in oncotis pressure?
Albumin
What does low albumin lead to?
Oedema
Low oncotic pressure
Fluid move capillaries into interstitium
What is fluid movement if low oncotic pressure?
Fluid move capillary into interstitium
Albumin
https://www.youtube.com/watch?v=B658Yn3INYc
Pressure higher at arterial or venule end capillary?
Greater arterial
Less venule
https://www.youtube.com/watch?v=B658Yn3INYc
Define insensible water loss? Ex
Define sensible water loss? Ex
Insensible- can’t measure
- lung, skin, resp, faeces
Sensible- urine, vomit
What is used to measure GFR?
Why?
Creatine
Freely filtered not absorbed
