Water Balance Flashcards
If a patient had sunken eyes, was refusing fluids, had a rapid pulse, dry mouth, weight loss, concentrated urine, low blood pressure and lack of skin turgor: what is likely to be wrong with them?
DEHYDRATION
Vomiting, diarrhoea, excessive sweating, low water intake, drainage from burns and damage to the hypothalamus can contribute to a deficit in what?
Body Fluids…. WATER
Chemical reactions that are important for acid balance occur in what?
Water
What is a major component of plasma and cells?
Water
What lubricates joints and organs?
Water
What has a high ability to absorb and retain heat, and stays in a liquid state over a broad range of temperature (0-100degrees)?
Water
What needs a large amount of heat to increase its temperature, and therefore is used to stabilise body temperature and can carry heat away from the body by sweating?
Water
How does sweating cool you down?
It absorbs heat away from the body and then evaporates on the surface of the skin
How many litres should our total body water be at any given time?
31-40 litres
Name 3 ways we take in water and how many mls:
Drinks - 1500mls
Food - 750 mls
Water of Metabolism - 250 mls
What 4 ways do we excrete water? (and give mls)
Urine - 1500 ml
Stools - 100 ml
Sweat - 200ml
Respiratory Loss - 700ml
Do men or women need more water in the body?
Men
What % of the male body is made up of water?
60%
Every cell in the body contains water. Where is 2/3 or 66% of it?
25 L is found in Intracellular Fluid (cells)
Every cell in the body contains water. Where is 1/3 or 30% of it?
Extracellular fluid 15 L
Interstitial = 12 L (between cells and not in blood vessels) Plasma = 3L (in blood)
Where is 3% of our water found?
0.7L is in our joints and CSF etc
Is there more water in the plasma or interstitial fluid?
There is more water in the interstitial fluid.
12L is found in between the cells whilst 3L is in blood.
There is even more in intracellular fluid = 25L.
What process allows substances to move in and out of cells?
Diffusion
Define simple diffusion
Movement from an area of high concentration to an area of low concentration: DOWN the gradient
What kind of membrane does diffusion cross?
Semi-permeable membrane
Name 5 factors that affect the rate of diffusion:
Temperature (higher = faster) Molecular Weight (larger = slower) Steepness of Gradient (steeper = faster) Membrane Surface Area (larger = faster) Membrane Permeability (more doors = faster)
Where will water always move to?
An area where it is less concentrated
What is a homogenous mixture of one or more dissimilar substances?
A solution
What is a solution usually made up of?
A liquid (solvent) and a solute (electrolyte/dissolved particle)
In what type of solution do small molecules dissolve and ionic compounds dissociate?
Aqueous Solutions
(the electrolytes dissolve and become ions with a charge so can conduct electricity - this is how we have nerve impulses)
What type of solution has proteins or other large molecules as a solute?
Colloids
e.g. blood - plasma proteins
What type of solution has even larger molecules than colloid solutions, where particles will settle if undisturbed?
Suspensions
blood also a suspension as red cell settle at bottom
pH is the concentration of what ions?
What type of pH does the body try and maintain?
Hydrogen
Neutral
Define osmotic pressure
The force (thrust) of water movement into the higher concentration solution
Name the 3 ways that the concentration of solutions can be measured as
g/L - Weight per volume
%
Moles - the number of molecules present in a sample, equal to the molecular weight in grams
What is the best way to measure a solution?
In moles
Define osmolarity
The number of osmoles per litre of solution
Osmotic concentration of body fluids has a great effect on cell function. It is dependent on number of particles dissolved.
So if urine has high osmolarity = more concentrate
More molecules dissolved = less water
Does water move faster if there is a high osmolarity?
Yes. The area will be more concentrated (less water) so water moves in faster
What does ISO-OSMOTIC mean?
Where two solutions have the same osmolarity
So plasma contains 300 mosmol of salt and glucose
Define tonicity
The ability of a solution to affect the cell (it depends on the concentration and the permeability of the membrane to the solute)
What is ISOtonic?
Same tonicity
What is HYPOtonic?
Low tonicity
What is HYPERtonic?
High tonicity
Can solutes cause water to move?
Yes if hypotonic or hypertonic
Does water move if the electrolytes outside the cell are equal to inside the cell?
No. It is isotonic and nothing will happen
What happens to the cell shape if it is isotonic
Nothing. The water will not move.
What happens to the cell shape if it is in a hypotonic solution?
It will swell and possibly burst.
This is because there is more water in the solution than in the cell.
(The solution has a low concentration of solutes that do not cross the membrane and a high water content).
The water therefore moves to where there is less water and into the cell.
What happens to the shape of a cell in a hypertonic solution?
It shrinks.
This is because there is not much water outside of the cell as there is lots of solutes. (Low water concentration and high concentration of solutes that do not cross membrane).
The water moves out of the cell to try and balance the concentration.
What mechanism tells the body we need more or less water?
Thirst
The amount of water in the body is detected by baroreceptors (that respond to pressure changes) and osmoreceptors (that detect changes in concentration if not enough fluid).
Where do these signals get picked up by?
Thirst centre in hypothalamus
If the hypothalamus picks up you need water, what 2 things does it do?
Releases ADH from PPG so less water in urine
Makes thirsty and gives dry mouth so want to drink
Name 4 treatments for dehydration
Fluid Therapy
Gelofusine (emergency as expands plasma and shrivels cells - hypertonic)
5% glucose solution - isotonic
0.9% saline - isotonic (don’t give to someone with high sodium levels)
What is hyponatraemia?
Overhydration/water intoxication
Where can’t excrete water
What will always result in a change in osmotic pressure (electrolytes on one side of membrane) therefore changing the cell in size?
Fluid movement
What does water always follow?
Salts
What is a universal solvent?
Water
What are the 3 fluid compartments in the body?
Extracellular - (interstitial and plasma)
Intracellular
What % of us is water?
60%
What do we call substances that are dissolved in solutions?
Solutes
Which of the following is the most concentrated solution?
0.9% saline
100g/l saline
9mg/100mls saline
100g/l
What is water balance interdependent on?
Electrolyte balance
When solutes move, what follows?
Water
What 4 electrolytes do we have in the body?
Sodium
Potassium
Chloride
Calcium
What process do electrolytes move across the plasma membrane by?
Diffusion
What process does water move across the plasma membrane by?
Osmosis
In a resting cell, is there more sodium, potassium and chloride inside it or outside it?
There is more potassium in the cell and less sodium and chloride
What is the most dominant extracellular ion?
Sodium
What ion creates osmotic pressure?
Sodium
Which ion is needed for nerve conduction and action potential?
Sodium
Which ion is controlled by ANP and aldosterone?
Sodium
What is hypernatraemia?
Too much sodium
NAtraemia
What is hyponatraemia?
Not enough sodium
Water loss, over-secretion of aldosterone and high dietary sodium can cause what?
Hypernatraemia
What can thirst, fever, convulsions and a raised blood pressure be a sign of?
(If there is an over secretion of aldosterone)
Hypernatraemia
What can vomiting, diarrhoea, burns or an inadequate dietary sodium intake cause?
Hyponatraemia
What could lethargy, confusion and a reduced blood pressure be a sign of in a burns victim?
Hyponaetremia
What is a balancing ion in the body?
Potassium
What ion is responsible for nerve conduction by returning a cell to its resting state after excitation?
Potassium
What is the normal serum range of potassium?
3.5-5.0 mmol/L
If there is more than 5 mmol/L of potassium in the body, what do we call this?
Hyperkalaemia
What could irritability, extreme muscle weakness or cardiac arrest be a sign of, in someone that has decreased renal excretion, burns or cell trauma?
Hyperkalaemia
(High cell trauma could allow potassium to leak out into body and heart is dependent on potassium and will rest too much)
If there is less than 3.5 mmol/L of potassium in the body, what do we call this?
Hypokalaemia
If a person has decreased tone in muscles, muscle cramps, bradycardia and an abnormal ECG, what could this be a sign of?
Hypokalaemia
As not enough potassium to return cells to resting state, puts strain on the muscles and heart muscle
Why is it important not to store blood for more than 21-35 days?
Red blood cells break down and leak potassium into the plasma. This makes it hyperkalaemic
Which ion has a normal plasma concentration of 9.4mg/100ml?
Calcium
What ion is required for muscle contraction and nerve excitability (it releases neurotransmitters from nerve cells)?
Calcium
Calcium is required for healthy bones and teeth. What other things is it needed for?
Muscle contraction and nerve excitability (it releases neurotransmitters from nerve cells)?
What do you call the condition where someone has too much calcium? What is its effects?
Hypercalcaemia - it causes excess hormone fatigue in the parathyroid gland and weakness as muscles don’t contract properly
What is the condition where there is not enough calcium?
Hypocalcaemia
What are the 2 side effects of hypocalcaemia?
Vitamin D deficiency
Muscle cramps due to neuromuscular excitability
What hormone can increase calcium in the body?
The parathyroid hormone, calcitonin
Name 4 electrolytes in the body other than calcium, potassium and sodium:
(MCBP)
Magnesium
Chloride
Bicarbonate
Phosphorous
What does magnesium do?
Affect other ions - balances their movement across membranes
Which ion plays an important role in the stomach (think hydrochloric acid) and helps balance other ions?
Chloride
Which ion promotes acid based balance?
Bicarbonate
Which ion (other than calcium) helps with bones and teeth?
Phosphorus
Can drugs ever cause an electrolyte imbalance?
Yes
Are electrolyte levels patient dependent?
Yes. All may have different levels.
For example a patient with renal failure may not be able to compensate for a change in electrolyte balance
What do exchange resins do?
They promote excretions of ions very quickly - however they should be used with caution as can have bad side effects
How do electrolytes get in and out of the cell?
The plasma membrane
What part of the cell helps maintain its homeostasis?
Plasma Membrane
Which part of the cell helps define cell boundaries, control interactions with other cells and regulates what goes in and out of the cell? (Selective permeability)
Plasma Membrane
When viewed with an electron microscope, what part of the cell looks like two dark parallel lines?
Cell membrane
What is the fluid mosaic theory and what part of the cell does it concern?
The cell membrane: proteins and carbohydrates sandwiched between two layers of phospolipid in an oily film
Pores in the cell membrane allow ……………. to go through
Proteins get through by c……………… or t……………….
Lipids get through by s……………. p………………….
Pores = Water Proteins = Channels or transporters Lipids = selective permeability
The membrane is made up of 90-99% of what and 1-10% of what?
90-90% lipids
1-10% of proteins
In the membrane, are lipids or proteins heavier?
Proteins. Even though there are less of them they are heavier and account for half its weight
The phospholipid bilayer is an excellent boundary. Describe where the heads and tails are located and their relationship with water:
The heads are hydrophilic and are outside
The tails are hydrophobic and are inside (wash hair feet dry)
What lipid makes the cell membrane fluid?
What happens if the concentration of this lipid is low?
Cholesterol - if the concentration of cholesterol is low then the membrane becomes more rigid. It is this lipid that make the membrane fluid.
What 2 things do membrane proteins do?
Cross the plasma membrane
Adhere to intracellular surface
Name 5 things that membrane proteins function as CM(A) R CCP CAM E
Cell-identity markers (antigens) Receptors Channels, carriers and pumps Cell adhesion molecules (which allow some cells to stick together) Enzymes
What part of the membrane functions as:
Cell-identity markers (antigens) Receptors Channels, carriers and pumps Cell adhesion molecules (which allow some cells to stick together) Enzymes
Membrane proteins
Some channel proteins in the plasma membrane are always open. What do they do?
Allow WATER and hydrophilic solutes to DIFFUSE in and out of the cells
What is apical transport?
The exchange between the cell apex and the lumen
What is basolateral exchange?
Where things are transported horizontally between cells (not out)
Channel proteins in the plasma membrane that are usually closed, only open in what 3 situations?
- When chemical messengers bind to them
- Voltage changes across the membrane
- They are mechanically stretched
What do channel proteins in the plasma membrane which open and close do? Why is this important?
They control the passage of electrolytes
Important in nerve signals and muscle contraction
What is the name of something that binds to solutes to transfer them across the membrane?
Carriers
What is the name for carriers that use ATP?
Pumps
What kind of role do carriers play?
A balancing role
Carrier mediated transfer of solutes is where:
Proteins in the cell membrane carry solutes through it
There are 2 types of carrier mediated transfer. What are they?
Passive and Active
Passive is facilitated diffusion (down the concentration gradient)
Active requires energy
Carrier mediated transfer is specific. What does this mean?
That each solute binds to a specific receptor on the carrier
The receptor is specific to only that type of solute
Can a carrier in active or passive transport become saturated?
Yes
What is facilitated diffusion?
It is where large molecules (that can’t cross the membrane) move down the concentration gradient (to an area there is less of them) with the help of a CARRIER. This does not require energy
Outline the 3 key steps of facilitated diffusion:
- Solute binds to carrier
- Carrier changes shape
- Carrier releases solute on the other side (e.g. glucose)
What is active transport?
Where molecules move against the concentration gradient and therefore the carrier requires ATP
(often used to pump things out of the cell that it doesn’t need)
Outline the 4 steps of active transport: (occurs in things like the sodium-potassium pump)
- Substance binds to carrier
- ATP phosphorylates carrier
- Carrier changes shape
- Carrier releases substance
The sodium-potassium pump uses ATP to get SODIUM OUT and POTASSIUM IN the cell.
What are its 2 main functions for doing this?
Regulating cell volume (after been excited)
Maintaining membrane potential
Define exocytosis
Eliminating or secreting material from the cell
So a protein may be made in the cell, which the cell then releases
Passive diffusion = no energy required and down the concentration gradient. What are the 3 types?
Osmosis and Filtration
Facilitated
Active transport requires energy as it is against the concentration gradient. It is c…………………. mediated and provides b….. transport
Carrier mediated
Bulk transport
All the electrolytes are higher outside the cell than inside the cell in its resting state than one. Which is this?
Potassium
Potassium is higher in the cell, whilst sodium, chloride and calcium are higher outside the cell
Which ion is responsible for osmotic balance, body fluid volume, nerve conduction and acid-base balance?
Sodium
Which ion is essential for gastric acid production and acts as a balancing ion?
Chloride
Which ion is needed for bone formation, muscle contraction, blood clotting and nerve impulses?
Calcium
Which ion is needed for nerve conduction, has a high concentration inside the cell, and converts carbohydrates to energy?
Potassium
Which ion is needed for acid based balance, bone formation, metabolism of carbohydrate and can be found in the DNA?
Phosphorous
In negative feedback control systems involved in homeostasis, what is the effector tissue in many cases?
Muscle or a gland
What type of tissue is found in the thyroid gland?
Simple cuboidal epithelium
The plasma membrane is freely permeable to what hormone?
Steroid hormones as they dissolve in the bylayer and diffuse into the cell
Is cartilage in the blood?
No
In homeostasis, is there continuous activity of sensory receptors?
Yes
What are the three basic fibre types in connective tissue?
Collagen
Reticular
Elastic
Is there less volume in extracellular or intracellular fluid?
Extracellular is only one third
When would haemolysis occur?
When blood cell is placed into a hypotonic solution
What type of cell lacks a nucleus?
Prokaryotic
Relative to the elbow, the wrist is what?
distal
