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Physiology 1 : renal > Control & abnormalities of body water > Flashcards

Control & abnormalities of body water Flashcards

1
Q

What happens if you add more water to a Na+ solution?

A

→ Hyponatremia

→ Concentration decreases

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2
Q

What happens if you remove water from a Na+ solution?

A

→ Hypernatremia

→ Concentration increases

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3
Q

What does osmolarity relate to?

A

→ Number of particles per unit volume of fluid

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4
Q

What does osmolality relate to?

A

→ Number of particles per unit weight of fluid

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5
Q

What is the equation for estimating plasma osmolarity?

A

→ 2[Na+] + 2[K+] + [glucose] + [urea]

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6
Q

What is normal plasma osmolality?

A

→ 275-295 mOsm kg-1

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7
Q

What does hypernatremia mean?

A

→ hyper osmolality

→ too little water

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8
Q

What does hyponatremia mean?

A

→ hypo-osmolality

→ too much water

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9
Q

What happens during diabetes mellitus?

A

→ Diabetes mellitus the glucose concentration rises
→ It contributes to the osmolality
→ high glucose concentration is filtered into the kidney tubule

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10
Q

What are osmoreceptors?

A

→ Sensory receptors located in the hypothalamus sense changes in osmolality of ECFV

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11
Q

What does an increase in osmolality stimulate?

A

→ Thirst

→ Secretion of vasopressin

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12
Q

How does ADH regulate plasma osmolality?

A

→Controlling water excretion and reabsorption

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13
Q

What does concentrated urine tell you about ADH levels?

A

→ ADH relatively high

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14
Q

Describe the loop of henle

A

→ Tubular fluid is iso-osmotic in the PCT
→ along the descending limb there is active reabsorption of Na+
→ Water moves out passively
→The loop has very concentrated interstitial fluid
→ in the ascending loop there is dilution of the tubular fluid as there is reabsorption of NaCl
→ at the DCT the tubular fluid is the most dilute

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15
Q

What is the effect of ADH on the collecting duct?

A

→ ADH binds to basolateral receptors

→ more water channels inserted in the luminal membrane

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16
Q

What is the mechanism ADH uses?

A

1) ADH binds to the receptor
2) Receptor activates cAMP
3) inserts AQP2 into apical membrane

17
Q

What is the function of ADH under normal conditions?

A

→ Osmoregulation

18
Q

What does a large drop in arterial pressure cause?

A

→ release of ADH

19
Q

Why is ADH secreted during hypovolaemia?

A

→ retention of water to increase blood volume

20
Q

What happens to plasma osmolality during severe haemorrhage?

A

→ Loss of BP is sufficient to stimulate ADH
→ decrease in plasma osmolality
→ ADH effect is always dilutional (adds pure water)

21
Q

What are the two systems activated during hypovolaemia?

A

→ RAAS occurs first

→ ADH secretion happens later

22
Q

What is the first line of defense against dehydration?

A

→ Thirst

23
Q

What kind of thirsts are there?

A

→ hyperosmotic

→ hypovolemic

24
Q

What is hyperosmotic thirst?

A

→ after eating a lot of salt

25
Q

What is hypovolemic thirst?

A

→ After losing a lot of blood

26
Q

What is the metabolic waste product in the kidney excreted as?

A

→ in a solute form

→ called the solute load

27
Q

How do you estimate the solute load?

A

→ body weight x 10

28
Q

How do you work out how much water is needed to excrete the solute load?

A

→ divide the urine concentration by the solute load

29
Q

What is water excess (hyponatremia)?

A

→ excessive water intake

→ impairment in renal water excretion

30
Q

What is water depletion (hypernatremia) ?

A

→ Insufficient water intake

→ Impairment in renal water reabsorption

31
Q

What are situations where water intake is continued but ADH is suppressed?

A 
→ vomiting , diarrhoea
→ Ecstasy 
→ Ectopic secretion of ADH (SIADH) 
→ Hypocortisolism 
→ Primary adrenal insufficiency ( Addisons)
32
Q

What is missing in people with Addisons?

A

→ Loss of cortisol

→ Loss of aldosterone

33
Q

What is the effect of Addisons?

A

→ Lack of sodium retention
→ Water is lost with it
→ hyponatremia due to water intake

34
Q

What are the major causes of SIADH?

A

→ TUMOR - ectopic production of ADH
→ CNS disturbance - trauma, stroke, infection
→ DRUGS - carbamazepine, prozac

35
Q

What are signs of SIADH?

A

→ Low plasma sodium
→ Low plasma osmolality
→ High urine osmolality

36
Q

How can water depletion from decreased intake of water occur?

A

→ Infants
→ Elderly
→ Individuals in a coma
→ Individuals with no access to water

37
Q

How can water depletion from increased loss of water through the kidney occur?

A

→ Diabetes mellitus

→ Impairment in ADH release

38
Q

What are nephrogenic causes of diabetes insipidus?

A

→ Mutation of ADH receptor
→ Mutation of ADH dependent H2O channels
→ Renal disease
→ Lithium

39
Q

What are central causes of diabetes insipidus?

A

→ genetic mutations
→ head trauma
→ disease of the hypothalamus /pituitary region

Physiology 1 : renal (13 decks)

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