Water, electrolyte, acid base

Question 1

Describe Body Fluids

Answer 1

• Typical adult body contains abotu 40L of body fluis
• 25L of fluids (63%) are located inside body cells, called intracellular fluid (ICF)
• 15L of fluids (37%) are located out of body cells, called extracellular fluid (ECF)
• 80% of ECF is interstitial fluid (which includes lymph, synovial fluid, CSF, GI tracts fluids, and fluids in the eyes and ears), and 20% of ECF is blood plasma
• ICF is mostly water and is ricj n K+, Mg+, HPO42-, SO42- and rotein anions.
• ECF contains mroe Na+, Cl-, HCO3- and Ca++

Question 2

What is a milliequivalents per litre

Answer 2

Question 3

Totla body volume and what it is composed of

Answer 3

• Concentrations of substances dissolved in ICF and ECF are constantly different beacuse the cell membrane is selectively permeable, which maintains a relatively unchanged distribution of substance sin different body fluids.
• Fluid balance refers to the proper levels of water and electrolytes beign the variour body compartments according to their needs
• Osmotic pressure (created by dissolved electrolytes in body fluids) and hydrostatic pressure (created by the water in body fluids) are the main forces behind any moleuclar movement between body compartments.

Question 5

Osmotic pressure vs hydrostatic pressure

Answer 5

• Osmotic pressure - minimum pressure whcih needs to be applied to a solution to prevent the inard flow of its pure solvent across a semi permeable membrane
• Hydrostatic pressure - pressure that is exerted by a fluid at equilibrium at a given point within the fluid due to the force of gravity/

Question 6

Water balance in the body

Answer 6

• Water is the most abundant constituent in the body, varying drom 45% to 75% of body weight. Water balance occurd when water intake equals water output.
• A normal adult consumes abot 2500ml of water daily 1500ml in beverages, 750ml in food and 250ml from cellular repsiration and anabolic metabolism/
• At the same time, this adult is releasing abotu 2500ml of water daily - 1500ml in urine, 700 by evaporation (skin and lung), 100ml fece, 200ml sweating.

Question 7

How we regulate water intake

Answer 7

1. The body loses as little as 1% of its water
2. An icnrease in osmotic pressure of ECF due to water loss stimulates osmoreceptors in the thirst centre (Hypothalamus).
3. Activity in he hypothlamus causes the person to be thirty and seek H20.
4. Drinking + the resulting distention of the stomach by water sitmulants nerve impulses that inhibit the thirst centre.
5. Water is absorbed through wall of stomach, small intestine and large intestine
6. The osmotic oressure of ECF fluid returns to nromal.

Question 8

Events in regulation of water output

Answer 8

Dehydration:

1. ECF becomes osmotically more concentrated.
2. Osmoreceptors in the hypothlaamic are stimualted by tbe increase in the osmotic pressur of body fluids.
3. The hypothalamic signala the psoterior piutuitary gland to release ADH in to blood
4. Blood carries ADH to kidney
5. ADH causes the distal convoluted tubules & collectin ducts to increase wate rreabsroption
6. Urine output decreases and further loss minimised,

Question 9

Thirts mechanism for regulating water intake

Answer 9

Question 10

ADH and its role in water regulaion

Answer 10

Question 11

Excess water intake

Answer 11

• Extracellular lfuid becomes osmotically less concentrated
• This change stimulates osmoreceptors in the hypothalamus
• The posterior pituitary gland decreases ADH release
• Renal tubules decrease water reabsorption
• Urine output, increases and excess waer is excreted

Question 12

What are electrolytes and what do they do?

Answer 12

Electrolytes are chemical substances that release cations (positively xharged ions) and anions (negatively charged ions) when they are dissolved in water. Electrolytes have 4 primary funcitons in the body

• Essential minerals (iodine, calcium)
• Control osmotsis between body compartments by establushing proper osmotic pressre (soidum, chloride)
• Help maintain acid-base balance (eg, hydrogen ion, bicarb ion)
• Carry electrical current that allows production of action potentials (eg, sodium, potassium)
• The most important electrolytes include Na+, K+, cl-, ca++ and HPO42-

Question 13

Na+ function

Answer 13

Na+ = most abundant extracellular cation; involved in nerve impulse transmission, muscle ocntraction and creation of osmotic pressure

Question 14

Cl- function

Answer 14

Cl- = major Extracllula anion, involved in regulating osmotic pessure between body comparments, forming HCL in stomach and involved in chloride shift process in blood.

Question 15

K+ function

Answer 15

Most abundant cation in ECF, involved in maintianing fluid volume, nerve impulse trnamsisison, muscle ocntraction and regulating pH.

Question 16

Ca++ function

Answer 16

Most abundant ion in the body, lcoated mainly in ecf, a major structural component of bones and teeth; functions in bblood clotting, NT release, muscle tone and excitability of nervous and muscle tissues

Question 17

HP04- function

Answer 17

HHP04-

• Important intracellular anion, another major structurral compoenent of bones and teeth , required for syntheses of nucleic acids and ATP and fror bifferin greations.

Question 18

Wat hormones regulate levels of electryolytes

Answer 18

• Alodtserone = from adrenal cortex, causes increase in sodium reabsorption and potassium secretions at th eindet tubules
• Parathyroid hprmone (pth) from parathyroud glands and Calcitoniia (CT) from the thyroid gand regulte calcium balance.

Question 19

Hw do we regulate electrolyrtes ( inputs and outputs)

Answer 19

• Electrolyte intake - usually in sufficient quantities in response ot hunger and thirst mechanism. in a evere electrolyte deficience, a person may experience salt crafin.
• Electorlyte output - Lost through perspiration, faeces and urine. The greatest electorlyte loss occurd as a result of kidne function
• Quantities lost vary with temp and exercoxe

Question 20

Electrolyte balance and hwo contorlled

Answer 20

1. Concentrations od Na/K+ ions and Ca2+ ions in the body fluid are very im[ortant.
2. The regulation of Na_/K+ ions ivle the secretion of Aldosterone from adrenal glanss
   
   • K+ ion conc incresse
   • Adrenal cortex signaled
   • Aldosterone secreted
   • Renal tibile inrease rebabsortoopn od Na+ ion and icnrease secretion of K) (increases risk K+ ions exreting)
   • Na_ ion are conserved and K+ exchanges.
3. Calcitonin from the thyroid gland and parathryoid homrone from the parathyroud glands regulate Ca+ ion concentration
   
   • PTH increases activity in bone resorbign cells (osteocytes and osteoclasts) which increase conc of both Ca+ and phsohate ions in ECF. Tgis hormone also causes increase absroption of Ca+ and increase excretion of phosphate from the kdiney.

Question 21

What are acids and bases and what primarily reuglates them?

Answer 21

• Acid ar eelctrolytes that release hydrogen ions (H+) when they are dissolved in water
• Bases are electrolytes that release hydroxide ions (OH-) when they are dissolved in water
• Acid base balance is primarily regulated by concentration of H+ (or the pH level) in body fluids, especially ECF

Question 22

WHat is the normal acid base balance and what are acid base buffer systems

Answer 22

• Normal pH rnage of ECF is from 7.35 - 7.45
• Most H+ comes from metabolism - glycolysis, oxidationof fatty acids and amino acids and hydrolysis of proteins
• Homeostasis of pH in bdy fluids is regulated by acid-base buffer systems (primary contorl), respiratory centres in brain stem and by kdiney tubule secretion of H+
• Acid-base buffer systems are chemical reactions that consist of a weak acid and a weak base, to prevent rapid, drastic changes in body fluid pH. One of the most carefully regulated cocnentration in body is that of h+ ion.

Question 23

Why is one of the most carefully rgeulated cocnentration in the body, H+?

Answer 23

• When acid (H+) is added to the blood, the pH decreases. Then increased acidity (decreased pH) is minimised by buffers which bind some of the added H+
• When acid is taken away, blood becomes more alkaline (ph Increases). This change is minimised by buffers, whcih release H+ adn rpelace some of the acid that was lost.

Question 24

Wh is the buffer system between H+ and hCO3- important in the body?

Answer 24

• H+ + HCO3- H2C03 H20+ CO2
• The pair bicabronate/cabronic acid forms an improtant buffer system. H2CO3 (carbonic acid) is the acid member of the pair because it can release H+.
• HCO3 - is the bade member of th epair because it can accept H+
• This system is important because 2 of its components re rigorously controlle dby the body; lungs control CO2 and kidney control HC03-

Question 25

Bicarbonate buffer systems

Answer 25

• Bicarbonate ion (HC03-) - converts storng acid into a weak acid
• Carbonic acid (H2C03) - converts storng base into weak base
• Bicarbonate buffer system produces carbonci acid (H2C03) and sodium bicarbonate (naHCO3) to minimise H+ increase, mainly in the blood

Question 26

Phosphate buffer system

Answer 26

Produces buffer systemL produces sodium hydrogen phosphates (NaH2PO04 and NA2HP04) to regulate H+ levels, mainly in kidney tubules and erythrocytes:

Question 27

Protein buffer system

Answer 27

Relies on the carboxylic acid group of amino acids t release H+ and the amino group to accept H+, mainly inside body cells and in blood plasma.

Question 28

How do respiratoy centres contribute to pH of bloods?

Answer 28

Question 29

How is bicarbonate conserved in the kidney

Answer 29

• Tubular cells are not permeable to bicarbonate, this, bicarbonate is conserved rather than reabsorbed. Steps 1 and 2 of bicarbonate conservation are indicated.

Question 30

Compensation to acid base balances and how

Answer 30

COmepnsations = series of physiological responses that react to acid-base imbalances, by returning blood pH to the nromal range (7.35-7.45)

• Respiratory acidosis. (due to deficiency of C02 expiration) and respirator alkalosis due to abnormally high CO2 expiratin) are primary disorders of CO2 pressure in the lungs. Thes emay be compensated by renal mechanisms wher epnephrons will secrete more h+ to correct acidosis and secrete less H+ to correct akalosis. It is due to increased C02 retention (due to hypoventilation), which can result in the accumulation of carbonic acid and this a fall in blood pH to below normal.
• Metabolic acidosis - increased production of acids such as lactic acid, fatty acis, and ketone bodies, or loss of blodo bicarbonate (such as by diarrhoea) resulting in a fall in blood pH to below normal.

Question 31

Type A intercalated cell funciton in acidosis an Type B intercalated cell function in alkalosis.

Answer 31

Question 32

Respiratory Alkalosis vs metabolic alkalosis

Answer 32

• Respiratory alkalosis - rise in blood pH due to loss of co2 and carbonic acid (through hyperventilatioN)
• Metabolic alkalosis - rise in blood pH produced by loss of acids (such as excessive vomiting) or by excessive accumulation of bicarbonate base

Question 33

Symtposm acidosis vs alkalosis

Answer 33

Question 34

Respiratory Excretion of CO2 and the respiratory centre

Answer 34

• The respiraotry centre is in te brain stem
• It helps control pH by regulating the rate and depth of breathing
• Increasing CO2 and H+ ions conc. stimulate chemo receptors associated with the respiratory centre, breathign rate and depth increase and CO2 concentration decreases.
• If the CO2 and H+ ion concentratiosn are low, the respiratory centre inhibits breathing.

Question 35

Renal excretion of H+

Answer 35

• Nephrons secrete hydrogen ions to regulate pH
• Phosphate buffer hydrogen ions in urine
• Ammonia produced by renal cells help transport H+ to the outside of the body: H+ + NH3 -> NH4+
• Chemical uffer system - (bicarbonate buffer system, phosphate buffer and protein buffer system) act rapidly and are the firts line of defence against pH shift
• Physiological buffer - (respiratory mechanism CO2 excretion), renal mechanis (H+ excretion) act slowly and are the 2nd line of defence against pH shift.

Question 36

Sources of H+

Answer 36

Question 37

Factors assoicated with Oedema

Answer 37

1. Low plasma protein concentration: cause is liver disease, kidney disease, loss of protein in urine, lack of protein in diet due to starvation.

Effect: plasma osmotic pressure decreases, less fluid enters venular end of capillaries by osmosis.

2. Obstruction of lymph vessels: causes are surgical removal of portions of lymphatic pathways and parasitic infections.

Effect: back pressure in lymph vessels, interferes with movement of fluid from interstitial spaces into lymph capillaries.

3. Increased venous pressure: venous obstruction or faulty valves.

Effect: back pressure in veins increases capillary filtration and interferes with return of fluid from interstitial spaces into venular end of capillaries.

4. Inflammation: cause is tissue damage.

Effect: capillaries become abnormally permeable and fluid leaks from plasma into the interstitial spaces.