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ILA formatives > ILA2- water and salt balance > Flashcards

ILA2- water and salt balance Flashcards

1
Q

How much of weight is water?

A

60% (42L), 40% (28L) Intracellular fluid (65% total water)

20% (14L) Extracellular fluid (35% total water)

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2
Q

Components of ECF

A

Intravascular (plasma) 25% (3L)

Interstitial 75% (11L)

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3
Q

Concentration of Na in ECF and ICF

A

Higher conc in ECF (135 mmol/L) than ICF (10mmol/L)

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4
Q

What are the 4 different causes of oedema?

A

Inflammatory, venous, lymphatic and hypoalbuminaemic

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5
Q

Main electrolyte in ICF?

A

Potassium

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6
Q

Predominant electrolyte in ECF?

A

Sodium (as NaCl and NaHCO3)

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7
Q

What are the majorly osmotically active substances in the ECF?

A

Sodium, chloride, glucose and urea

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8
Q

Define osmole.

A

Unit of osmotic pressure equal to the molecular weight of a solute in grams divided by no. of ions into which is dissociates in solution

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9
Q

Define osmosis.

A

Passage of a solvent from a less concentrated to a more concentrated solution through a semi permeable membrane. Equalise concentration of both solutions. IN living organisms the solvent is water

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10
Q

Define osmolality.

A

Concentration of a solution, expressed in osmoles, of solute particles per kg of solvent

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11
Q

Define oncotic pressure.

A

Form of osmotic pressure exerted by proteins, notably albumin, that tends to pull fluid into its solution

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12
Q

Define osmotic pressure.

A

Pressure by which water is drawn into a solution through the semi permeable membrane, more concentrated solution=greater pressure

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13
Q

Define osmolarity

A

measure of the osmotic pressure exerted by a solution across a semi-permeable membrane compared to water. Depends on number of particles in a solution

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14
Q

Where is albumin produced?

A

Liver

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15
Q

What are the functions of albumin?

A

Bind to substances in the blood for transportation

Regulation of oncotic pressure of the blood

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16
Q

How does low albumin lead to oedema?

A

Lower oncotic pressure -> lack of re-absorption back into capillary at venous end ->build up of fluid in interstitial space/ tissues

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17
Q

Causes of low albumin?

A

Liver failure (production) and kidney failure (increased loss)

18
Q

What are the key routes of water loss from the body?

A

Urine (1.5L/day), faeces (0.1L/day), insensible (cant be sensed) (0.9L/day), females vaginal secretions (0.05 L/day)

19
Q

Where are the osmoreceptors found?

A

Hypothalamus

20
Q

How are osmoreceptors stimulated?

A

Osmotic pressure of the blood changes ->water diffusion changes -> they expand when blood more dilute and vice versa -> afferent impulse to hypothalamus to increase or decrease ADH production
Stretch= too much water= less ADH

21
Q

What does arginine vasopressin (ADH) do?

A

Increases amount of aquaporin 2 in the collecting duct epithelium of nephrons in the kidneys

22
Q

Where is ADH released from?

A

Posterior pituitary

23
Q

What does aldosterone do?

A

Stimulates active re-absorption of Na and H2O

24
Q

Describe the renin-angiotensin-aldosterone system (RAAS)

A

1) Decrease in water in ECF results in decreased circulating volume
2) Decreased renal blood flow
3) Renin released from kidneys
4) Renin stimulates release of angiotensin which in turn stimulates release of aldosterone
5) Angiotensin and aldosterone stimulate:
- Increased sodium reabsorption in the kidneys in exchange for potassium or hydrogen excretion
- ADH release
- Sodium reabsorption brings water with it to return water in ECF to normal

25
Q

How is thirst caused?

A

Insuffiency of water results in an increased osmolality in extracellular fluid. This is sensed by osmoreceptors in the organum vasculosum of the lamina terminalis which triggers thirst

26
Q

Describe the action of ADH when fluid deficiency

A

1) Sensed by the osmoreceptors in the organum vasculosum of the lamina terminalis and subfornical organ
2) These areas project to the supraoptic nucleus and paraventricular nucleus which contain neurons that secrete ADH from nerve endings in the posterior pituitary
3) Increases water reabsorption at kidneys collecting ducts
4) Peptide hormone which increases water permeability of the kidneys collecting duct and distal convoluted tubule by inducing translocation of aquaporin-CD water channels in the plasma membrane of collecting duct cells
5) Aquaporins allow water to move down their osmotic gradient and out of the nephron, increasing the amount of water re-absorbed from the filtrate (forming urine) back into the bloodstream

27
Q

Action of aldosterone in times of fluid deficiency

A

1) Decrease in water in ECF results in decreased circulating volume
2) Decreased renal blood flow
3) Renin released from kidneys
4) Renin stimulates release of angiotensin which in turn stimulates release of aldosterone
5) Angiotensin and aldosterone stimulate:
- Increased sodium reabsorption in the kidneys in exchange for potassium or hydrogen excretion
- ADH release
- Sodium reabsorption brings water with it to return water in ECF to normal

28
Q

What is ramipril?

A

ACE inhibitor, interferes with RAAS, used to treat hypertension

29
Q

what is bendroflumethazide?

A

Thiazide diuretic. Prevents body absorbing too much salt. Treats hypertension.

30
Q

What is amoldipine?

A

Ca channel blocker, causes vasodilation. Treats hypertension

31
Q

What is lanzoprazole?

A

Proton pump inhibitor. Decreases amount of acid produced in stomach. Treat heartburn, can prevent stomach and intestinal ulcers

32
Q

Total body water is distributed in 3 compartments. How is TBW distributed by volume?

A

INTRACELLULAR 28L INTERSTITIAL 11L INTRAVASCULAR 3L

33
Q

Osmolality can be calculated from blood results. Which of the following is a factor in calculating osmolality?

A

UREA (protein)

34
Q

What describes the relationship between albumin and oedema?

A

A LOW ALBUMIN CAUSES AN INCREASE IN ONCOTIC PRESSURE AND WATER DIFFUSES FROM THE INTERSTITIAL FLUID INTO THE BLOOD

35
Q

Plasma osmolality: 2[Na+ + K+] +glucose+Urea. Why is sodium doubled?

A

To account for negatively charged ions

36
Q

Example of an insensible loss?

A

RESPIRATION
Insensible loss: Water loss from body which we cannot perceive or are aware of. Not solute only solvent. Cannot be measured
Sweat is not as contains solute
Insensible loss increases by 10% per degree increase in temp

37
Q

Site of ADH synthesis?

A

Hypothalamus, released from posterior pituitary

38
Q

What affect does drinking water do to serum osmolarity?

A

Reduces

39
Q

Principle site of renin synthesis?

A

JUXTAGLOMERULAR CELLS OF THE KIDNEY

40
Q

Action of renin?

A

ANGIOTENSINOGEN → ANGIOTENSIN 1

41
Q

Site of synthesis of aldosterone?

A

ADRENAL CORTEX

ILA formatives (10 decks)

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