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My Anatomy and Physiology > 3. Solutions and Concentrations > Flashcards

3. Solutions and Concentrations Flashcards

1
Q

What are the symptoms of dehydration?

A

Sunken eyes

Lack of skin turgor

Low blood pressure

Concentrated Urine

Weight loss

Dry mouth

Rapid pulse

Refusing fluids

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2
Q

What causes dehydration?

A

Vomiting

Diarrhoea

Excessive sweating

Low water intake

Drainage from burns

Damage to thirst mechanism

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3
Q

Why do we need H2O?

A

Universal solvent

Chemical reactions occur in water

Found as major component of plasma and cells.

Lubricant of joints, organs

High ability to absorb and retain heat as stays in liquid state over broad range (0-100 0C) of temperature

Large amount of heat required to increase­ its temperature (this stabilises body temperature plus sweating carries a lot of heat away from body)

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4
Q

Where does our body water come from?

A

Drinks 1500ml

Food 750ml

Water of metabolism 250ml

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5
Q

How much water is in our body?

A

32-40L approx 60%

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6
Q

Where do we lose water from our bodies?

A

Urine 1500ml

Stools 100ml

Sweat 200ml

Respiratory loss 700ml

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7
Q

Where is the water in the body?

A

Intracellular fluid 25L=2/3=66%

Extracellular fluid/Interstitial fluid 12L=30%

Plasma 3L=7.5%

Joints, CSF 0.7L

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8
Q

What are aquaporins?

A

Semi-permeable membranes

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9
Q

Define simple diffusion?

A

Movement from an area of high concentration to an area of low concentration through a semi-permeable membrane.

This is passive.

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10
Q

Define defusion?

A

Allows substances to move in and out of cells e.g. organelles, large proteins, blood etc

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11
Q

What factors affect diffusion rate?

A

Temperature i.e. Increased temperature increases motion of particles

Molecular weight i.e. Larger molecular weight means particles move slower

Steepness of conc. gradient i.e. increased difference, increased rate

Membrane surface area i.e. increased area increased rate

Membrane permeability i.e. increased permeability, increased rate

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12
Q

Define osmosis?

A

Movement of water down its concentration gradient accross a semipermiable membrane

This is passive

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13
Q

What is a solution?

A

A homogenous mixture of one or more dissimilar substances

Usually a liquid (solvent) and a solute (electrolyte - dissolved particle)

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14
Q

What are the three types of solutions?

A

Aqueous solutions

Colloids

Suspensions

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15
Q

What is an aqueous solution?

A

Small molecules dissolve

Ionic compounds dissociate into anions (-ve) and cations (+ve)

Electrolytes are soluble inorganic molecules whose ions conduct electricity in solution

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16
Q

What is a colloid?

A

A solution where proteins or other large molecules as solute e.g. plasma or albumin

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17
Q

What is a suspension?

A

A solution with even larger molecules than colloid solutions

Particles settle if undisturbed

18
Q

What is pH?

A

A low pH is acidic with a high amount of H+ ions, a high pH is basic with a high amount of OH- ions

The body has a pH of 7.35

19
Q

What is osmotic pressure?

A

The pressure exerted by water in a solution

OR

Exerted by solutes drawing water into area of low water

OR

The force (thrust) of water movement into the higher concentration solution

OR

The amount of hydrostatic pressure required to stop osmosis

OR

Pull of fluid from high -> low concentration

e.g. NA has high osmotic pressure as it pulls water across semi permeable membrane

20
Q

How can the concentration of solutions be measured?

A
  1. ) g/L - weight per volume
  2. ) % - weight in grams per 100ml
  3. ) Moles of solute per litre i.e. 1 mole = Number of atoms/molecules present in a sample equal to the molecular weight in grams

so 1 mole H2=1 mole O2=1 mole NaCl same concentration

21
Q

Why use moles?

A

Gives better ability to comare as number of molecules in solution is more important

22
Q

What is osmolarity?

A

Number of osmoles/L solution (H20)

Dependent on number of particles dissolved rather than the weigh of the molecule

23
Q

What is osmolality?

A

Number of osmoles/kg (H20)

24
Q

How do you measure osmotic concentration?

A

Osmoles/L or Kg

25
Q

What is 1 osmole?

A

1 mole of dissolved particles i.e. 1 mole of NaCl contains 1 mole of Na+ ions and 1 mole of Cl- ions = 2 osmoles/L

26
Q

What does iso-osmotic mean?

A

Having the same osmotic pressure e.g. 300 mosmol Glucose, 300 mosmol NaCl, 300 mosmol Plasma

Same osmolarity so isoosmotic to each other

mosmol=milli osmol=1/1000 osmol

27
Q

Define tonicity?

A

Ability of a solution to affect the cell

Depends on concntration and permeability of the membrane to the solutes

28
Q

What does isotonic mean?

A

Same tonicity

29
Q

What does hypotonic mean?

A

Having a lower tonicity than a particular fluid

30
Q

What does hypertonic mean?

A

Having a higher tonicity than a particular solution

31
Q

What is the tonicity inside and outside the cell?

A

Isotonic

Concentration of electrolytes outside the cell is equal to that inside the cell

No water movement

No change in cell shape

32
Q

What do hypotonic solutions in the body do?

A

Has low concentration of solutes that do not cross the membrane

High Water content (more water, less solute)

Cell absorbs water, swells and may burst (lysis)

NOT IDEAL

33
Q

What do hypertonic solutions in the body do?

A

Low water concentration and high concentration of solutes that do not cross the membrane

Water moves out of cell to try and balance water/ion concentation

Cells lose water and shrivel up

NOT IDEAL

34
Q

How does the body tell us we need more water?

A

Thirst

35
Q

What happens in the body when body water decreases?

A

Osmoreceptors sense changing conc.

Baroreceptors sense changing pressure

These are communicated to thirst centre in hypothalamus

Hypothalamus tells posterior pituitary to release ADH to reabsorb more water from urine and sends message to make mouth drier which makes you feel thirsty and makes you drink

This is negative feedback

36
Q

What are the treatments for dehydration?

A

Fluid therapy

Gelofusine (plasma expander, increases volume of fluid, isotonic to replace blood loss)

0.9% saline (0.9g saline in 100ml of water)

5% glucose/dextrose solution (5g glucose in 100ml of water)

37
Q

What two problems can result from overhydration?

A

Hyponatraemia (low sodium)

Water intoxication

e.g. ecstasy - take too much water, dilutes body fluids, cell swell, lysis

38
Q

What is hydrostatic pressure?

A

The force exerted on the membrane by water/fluid

In a resting cell this will be stable as intracellular=interstitial

39
Q

What influences water movement?

A

Hydrostatic pressure

Movement of fluid between compartments through a selectively permeable membrane driven by hydrostatic pressure

40
Q

What effect does fluid movement have?

A

Any fluid movement results in a change in osmotic pressure (electrolytes on one side of membrane) therefore cell will change size

Water will always follow salts

My Anatomy and Physiology (8 decks)

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