Lecture 12

Question 1

How much of the body is water?

Answer 1

60%

Question 2

How much of the fluid is ECF and ICF, plasma and interstitial fluid?

Answer 2

-ICF=40% -ECF=20% -Plasma: 5% -Interstitial and trans-cellular: 15%

Question 3

How much ECF is in a newborn?

Answer 3

+20% so in total 40%

Question 4

How many liters of plasma are there in a 500kg horse?

Answer 4

5% is the plasma can work out how much plasma in a 500kg horse- 5%x 500kg= 25 liters of plasma -imprtant in vet practise, not taking too much etc in newborns a bit different proportions

Question 5

What are the components of ECF?

Answer 5

• Cations: Na+, K+, other -Anions: Cl-, HCO3-, other - plasma proteins -(other includes urea and glucose)

Question 6

What are the components of ICF?

Answer 6

-Cations: K+, Na+, other - Anions: PO43-, protein anions, other -(other includes urea and glucose)

Question 7

What is the importance of the electrolytes in the fluid?

Answer 7

-where the electrolytes are =major influence on where the fluid will be

Question 8

What are the most abundant electrolytes?

Answer 8

-intracellular- K+ is the most abundant, followed by Na+

Question 9

What are the protein anions important for?

Answer 9

anions- PO4 3-, protein anions= not able to cross across the membrane, fixed, stay inside the cell= important to stabilise the balance between the ICF and ECF

Question 10

How is ECF volume controlled?

Answer 10

-what controls the ECF volume= change in plasma volume can cause change in blood pressure and that drives change in ICF -change in blood pressure drives change in GFR (glomerulal filtration rate)= which changes the renin/aldosterone-that changes Na reabsorption -Na conc important= if need Na means have to lose K or H- a problem? = no! thanks to what they eat hay has some of Na and lot of K so losing K is not an issue

Question 11

What is the deal with K and Na concentration in carnivores and herbivores?

Answer 11

–usually get more K than Na especially herbivores -have to get rid of excess K! lost in urine and faeces herbivores- need to keep their Na as it has major role in keeping the plasma volume stable carnivores- not as dramatic difference but have more K as well -Herbivores: Na conservers / K wasters

Question 12

How is blood volume regulated?

Answer 12

-decrease in Na means a drop of arterial blood pressure -that decreases GFR so less Na is filtered -it also increases production of aldosterone that stimulates increase in Na+ reabsorption =this mean decrease in Na+ and accompannying Cl and fluid =rise in conservation of NaCl and accompanying fluid

Question 13

What is the most efficient way of measuring dehydration?

Answer 13

-BW= body weigt = most efficient way of how to measure hydration state -if quick loss of weight usually means lot of water loss -however have to have weights to compare- not as practical

Question 14

What can PCV tell us about hydration?

Answer 14

-can tell us about hydration, proportions go up if dehydrated as red blood cell count

Question 15

How is total protein affected when dehydrated?

Answer 15

-total protein, higher proportion of proteins then there is less water

Question 16

What happens when there is 5-7% drop in bodyweight (fluid)?

Answer 16

-skin-(decrease in skin elasticity) one of the first to be affected by loss of water- asses the skin to look for signs of dehydration -then asses what happens in circulation= do capillary refill- look at the gums, press on them, take the finger away, then the white spot should quickly refill and be pink again= if dehydrated around 3 seconds till the blood comes back= decrease in capillary refill (takes longer)

Question 17

What happens when there is 8-10% drop in bodyweight (fluid)?

Answer 17

-sunken eyes- usually lot of fluid in the back of the eyes, lack of fluid= eyes go back as not enough fluid, depression= not enough circulation in brain, decrease in capillary refill= cr - severe dehydration

Question 18

What happens when there is more than a 10% drop in bodyweight (fluid)?

Answer 18

–more than 10% life threatening = cephalic vein put liquid in! -cold extremities, lying down= recumbent

Question 19

What is the normal ECF/ICF osmolarity?

Answer 19

main regulation=-vasopressin / thirst -300 mosmols/ml -ICFosmolarity = ECFosmolarity -balanced by (total Na + total K) /Total Body Fluid Plasma[Na]

Question 20

When does hypertonicity in ECF/ICF arise?

Answer 20

-decrease in H20 intake or retention

Question 21

When does hypotonicity in ECF/ICF arise?

Answer 21

-stress, increase in H20 intake and retention and kidney failure

Question 22

How is osmolarity regulated in the body?

Answer 22

-decrease in ECF volume decreases arterial blood pressure -that is detected by Left atrial volume receptors (important only in large changes in plasma volume/arterial pressure) -that stimulates the hypothalamus to increase thirst and to release vasopressin -vasopressin stimulates arterial vasoconstriction (which increases arterial blood pressure) and increases H2O permeability of distal and collecting tubules -that increases H20 reabsorption which decreases urine volume output -that increases plasma volume and decreases plasma osmolarity -when the plasma osmolarity rises that stimulates the Hypothalamic osmoreceptors (dominant factor controlling thirst and vasopressin secretion -those stimulate thirst and vasopressin -increase in thirst increases H20 intake which decreases plasma osmolarity and increases plasma volume

Question 23

What is the pH compatible with life?

Answer 23

-6.8 to 8 -on either side= death -average 7.4 in blood

Question 24

What is the Henderson-Hasselbalch equation?

Answer 24

-pH = pK + log[HCO3-]/[CO2] -pk is always 6.1 and it is the constant log of conc of bicarb divide by CO2 concentration

Question 25

What are the sources of acid in the body in the acid-base balance?

Answer 25

-Source of acid: -H2CO3 -Nutrient breakdown -Metabolism (fatty acids, lactic)

Question 26

What are the sources of buffers in the body in the acid-base balance?

Answer 26

-Buffers: -HCO3- -proteins(ICF) - Haemoglobin -PO43-

Question 27

How is pH regulated by the kidney?

Answer 27

-when plasma H+ or CO2 rises -the kidney increases H+ secretion and increases HCO3- conservation -that leads to an increase in H+ excretion and decrease in HCO3- excretion -that in turn decreases the plasma H+ and increases the plasma HCO3- (buffers)

Question 28

How is pH renaly regulated?

Answer 28

- H+ secretion (rather than K) - HCO3- filtration - NH3 (from glutamine) - PO43- (buffer)

Question 29

What are the abnormalities in the acid base balance?

Answer 29

-Respiratory acidosis: hypoventilation -Respiratory alkalosis: hyperventilation -Metabolic acidosis: diarrhea, dehydration -Metabolic alkalosis: HCO3- ingestion -Compensation

Question 30

What is respiratory acidosis?

Answer 30

pH-7.1 - medical condition in which decreased ventilation (hypoventilation) causes increased blood carbon dioxide concentration and decreased pH (a condition generally called acidosis). -Carbon dioxide is produced continuously as the body's cells respire, and this CO2 will accumulate rapidly if the lungs do not adequately expel it through alveolar ventilation. Alveolar hypoventilation thus leads to an increased PaCO2 (called hypercapnia). The increase in PaCO2 in turn decreases the HCO3−/PaCO2 ratio and decreases pH. -Metabolism rapidly generates a large quantity of volatile acid (H2CO3) and nonvolatile acid. The metabolism of fats and carbohydrates leads to the formation of a large amount of CO2. The CO2 combines with H2O to form carbonic acid (H2CO3). The lungs normally excrete the volatile fraction through ventilation, and acid accumulation does not occur. A significant alteration in ventilation that affects elimination of CO2 can cause a respiratory acid-base disorder. The PaCO2 is maintained within a range of 39–41 mm Hg in normal states. Alveolar ventilation is under the control of the central respiratory centers, which are located in the pons and the medulla. Ventilation is influenced and regulated by chemoreceptors for PaCO2, PaO2, and pH located in the brainstem,and in the aortic and carotid bodies as well as by neural impulses from lung stretch receptors and impulses from the cerebral cortex. Failure of ventilation quickly increases the PaCO2. In acute respiratory acidosis, compensation occurs in 2 steps. The initial response is cellular buffering that occurs over minutes to hours. Cellular buffering elevates plasma bicarbonate (HCO3−) only slightly, approximately 1 mEq/L for each 10-mm Hg increase in PaCO2. The second step is renal compensation that occurs over 3–5 days. With renal compensation, renal excretion of carbonic acid is increased and bicarbonate reabsorption is increased. For instance, PEPCK is upregulated in renal proximal tubule brush border cells, in order to secrete more NH3 and thus to produce more HCO3−.[1]

Question 31

What is metabolic acidosis?

Answer 31

-pH 7.1 -condition that occurs when the body produces too much acid or when the kidneys are not removing enough acid from the body. If unchecked, metabolic acidosis leads to acidemia, i.e., blood pH is low (less than 7.35) due to increased production of hydrogen ions by the body or the inability of the body to form bicarbonate (HCO3-) in the kidney. Its causes are diverse, and its consequences can be serious, including coma and death.

Question 32

What is respiratory alkalosis?

Answer 32

-pH 7.7 - medical condition in which increased respiration (hyperventilation) elevates the blood pH (a condition generally called alkalosis). -Respiratory alkalosis generally occurs when some stimulus (see "Causes" below) makes a person hyperventilate. The increased breathing produces increased alveolar respiration, expelling CO2 from the circulation. This alters the dynamic chemical equilibrium of carbon dioxide in the circulatory system, and the system reacts according to Le Chatelier's principle. Circulating hydrogen ions and bicarbonate are shifted through the carbonic acid (H2CO3) intermediate to make more CO2 via the enzyme carbonic anhydrase according to the following reaction: The net result of this is decreased circulating hydrogen ion concentration, and thus increased pH (alkalosis). There is also a decrease in ionized blood calcium concentration.

Question 33

What is metabolic alkalosis?

Answer 33

-pH 7.7 - a metabolic condition in which the pH of tissue is elevated beyond the normal range ( 7.35-7.45 ). This is the result of decreased hydrogen ion concentration, leading to increased bicarbonate, or alternatively a direct result of increased bicarbonate concentrations.