Body fluids and oedema

Question 1

Define ‘homeostasis’

Answer 1

Homeo = sameness
Stasis = standing still
The process whereby cells, tissues, and organisms main tain the status quo

Question 2

Compare and contrast water balance in m & f

Answer 2

Standard: m 60%, f 50%, i 70%
Lean : m 70%. f 60%, i 80%
Obese/old : m 50%, f 42%, i 60%

Question 3

How much water is in each compartment?

Answer 3

ICF : 2/3, ECF : 1/3, IF : 4/5 of ECF, Plasma : 1/5 of ECF

Question 4

Outline differences between dehydration and water toxicity

Answer 4

Dehydration :
- due to water loss
- solute con. in extracellular fluid increases, tissue fluid becomes hypertonic to cell, water leaves cell
- caused by excessive sweating, vomitting diarrhea
- moderate dehy. signs - dry mouth, sunken eyes, skin does not bounce back after light pinching
- sever dehy. signs - pulse and breathing rate rapid, hands and feet cold, lips are blue
cure - low-sodium solution

Water toxicity :

• due to gain in water
• solute con. in ECF d, tissue flui hypo to cells, water enter cells
• oedema, swelling in brain
• signs : nausea, vomitting, colapse
• cure : high con. of sodium solution

Question 5

Explain concepts behind positive and negative feedback loops

Answer 5

NFM : stimulus causes opposite output in order to maintain an ideal level
stops when effector ceases
PFM : output exaggerates the original stimulus
stops when stimulus ceases

Question 6

Explain importance of acid-base balance for normal human physiology

Answer 6

• Human tissue survival (pH 6.8-7.8)
• prevent acidosis from increased metabolism/lactic acid build up
• prevent alkalosis due to hyperventilation
• prevent deaths when pH>7.8 or pH<7

Question 7

Normal range of pH in tissues including blood

Answer 7

7.8 < death
7.45 < alkalosis
7.45 (arteries)
7.4
7.35 (veins)
7.35 > acidosis
7 > death

Question 8

Normal range of core body temperature

Answer 8

37 +- 0.5

Question 9

Mechanisms that regulate pH and core body temperature

Answer 9

Body Temperature :
Hot
Vasodilation - Arterioles dilate, more blood enters skin, capillaries and heat is lost
Sweating - Sudorific glands secrete sweat- removes heat when water changes state
Pilorelaxation - hairs flatten
Stretching out - increase surface area of body

Cold
Vasoconstriction - Arterioles get smaller, reduce blood going to skin
Shivering - Rapid contraction and relaxing of muscles - heat produced by respiration
Piloerection - Hairs on skin stand up
Curling up - decrease surface area

pH :

• acidosis - due to increased metabolism/lactic acid build up
• CO2 blow off from lungs into paper bag
• alkalosis - due to hyperventilation
• breathing rate reduced to increase CO2 in blood

Usage of kidney :

• if blood acidotic - kidneys excrete H+ and retain HCO3-
• if blood alkylotic -kidneys excrete HCO3- and retain H=

Question 10

Process of oedema

Answer 10

• Oedema is swelling of body’s tissue due to excess interstitial fluid retention
• Occurs when hydrostatic pressure > osmotic pressure
• Inc. hydro.p due to venous obstruction/heart failure
• More fluid leaks out of intravascular compartment
• Occurs when plasma proteins in interstitial space (due to damage of blood vessel wall)
• ## plasma protein pulls water from intravascular comp. into interstitial space