Water

Question 1

What portion of adult body water weight is found intracellularly?

Answer 1

2/3

-

Question 2

Water is an excellent solvent for what?

Answer 2

ionic compounds and solutes such as glucose and AA’s

Question 3

Children have more water than adults in which compartment?

Answer 3

extracellular

Question 4

Water weakens what forces?

Answer 4

electrostatic forces and hydrogen bonding between other polar molecules

Question 5

Water is involved in what type of reactions?

Answer 5

hydrolytic (peptide hydrolysis)

Question 6

Water is produced in the body by what?

Answer 6

oxidative metabolism of hydrogen-containing substrates

- 300 ml/day

Question 7

In what 3 ways does water act as a carrier?

Answer 7

1. transports nutrients and removes wastes
2. allows exchanged between cells, interstitial fluid, and capillaries
3. maintains vascular volume and blood circulation

Question 8

How does water act in thermogenesis?

Answer 8

1. waters large heat capacity helps limit body temp fluctuations
2. water has large capacity for heat vaporization
3. sweating and evaporation allows heat loss

Question 9

How does water act as a lubricator?

Answer 9

forms lubricating fluid for joints, saliva, gastric, intestinal, genito-urinary, and airway mucus.

Question 10

How does water act as a shock absorber?

Answer 10

Maintains cellular shape and allows imbibition

Question 11

What important function does water have for the brain and fetus?

Answer 11

Forms CSF for brain and spinal cord protection and suspends fetus

Question 12

What is activated with increase in internal body temp?

Answer 12

Activation of sweat glands

Question 13

How many KJ of heat is lost by evaporation of 1 gram of water?

Answer 13

2.2 KJ

Question 14

What is sweat compared to plasma or extracellular fluid?

Answer 14

Hypotonic

Question 15

Intense sweating leads to greater water than electrolyte losses and results in what type of dehydration?

Answer 15

Hypertonic (fluid replacement is more important that salt!!)

Question 16

The osmotic pressure of extracellular fluid increases when?

Answer 16

When water losses exceed water intake

Question 17

Is ADH release or the hypothalamic thirst reflex triggered first?

Answer 17

ADH release (1% osmolarity increase)

Question 18

What is the most important stimulus controlling thirst?

Answer 18

Osmoreceptor input

Question 19

What is the cornerstone of clinical assessment of hydration status?

Answer 19

Urine and blood assays

Question 20

High grades of urine color can also indicate what?

Answer 20

Gross hematuria or bilirubin excretion from jaundice

Question 21

For hydration status, urine osmolarity is inferior to what?

Answer 21

Plasma

Question 22

What is the most widely used hematological index of hydration?

Answer 22

plasma osmolarity

- greater than 300 mmol/Kg –> dehydration

Question 23

What can affect bioelectrical imedance analysis?

Answer 23

• alcohol consumption
• diuretics
• menstrual cycle
• ilness

Question 24

How can total body water be measured?

Answer 24

using deuterium oxide (stable hydrogen isotope)

Question 25

What are the 3 types of dehydration?

Answer 25

1. isotonic - net salt and water loss is equal 2. hypertonic - water loss or excess salt 3. hypotonic - loss of salt or excess water

Question 26

Mild dehydration (1-2%) can impair what?

Answer 26

cognitive functions and physical performance

Question 27

Moderate dehydration (2-5%) can result in what?

Answer 27

- hyperthermia - reduced SV, CO, BP, and bloof low - fatigue

Question 28

How does dehydration impair cognition?

Answer 28

underperfusion of brain and increased stress hormones

Question 29

Sever dehydration leads to what?

Answer 29

- dizziness, lethargy, irritable - confusion - ortho hypotension - tachycardia

Question 30

What 3 factors make infants more vulnerable to fluid/electrolyte imbalance?

Answer 30

1. high surface-to-body-weight ratio 2. limited ability to secrete solutes and concentrate urine 3. low ability to express thirst and high metabolic rate

Question 31

What 6 factors lead to decreased fluid intake and increased fluid

Answer 31

1. elderly have less thirst (hypodipsia) 2. defects in osmoreceptors, baroreceptors, and central reg mechanisms 3. decreased urine concentration, renin activity, aldosterone, and ADH resistance 4. reduced access to fluids 5. diuretics or laxatives 6. fear of incontinence

Question 32

Drinking to thirst is not advised in what conditions?

Answer 32

- congestive heart failure - end-stage renal disease - COPD

Question 33

What are the short term effects of water consumption?

Answer 33

- increased satiety - reduced hunger - increased energy expenditure from water induced thermogenesis

Question 34

Excess water combined with glycerol creates what?

Answer 34

as osmotic gradient for temporary water retention

Question 35

What is hyponatremia?

Answer 35

when blood sodium levels fall bellow 135 mmol/L

Question 36

Hyponatremia causes what?

Answer 36

brain swelling --> seizures, coma, and death

Question 37

Symptoms of hyponatremia include...

Answer 37

headache, nausea, fatigue, confusion | - these can mimic heat illness (dehydration)