4. Electrolytes and Transport Mechanism Flashcards
Why is water balance interdependent with electrolyte balance?
Solutes move, water follows
How do electrolytes move across plasma membranes?
Electrolytes move across plasma membrane by diffusion then water follows by osmosis
What electrolytes are outside the cell?
Na+ 150 mmol/L
K+ 5.5 mmol/L
Cl- 125 mmol/L
What electrolytes are inside the cell?
Na+ 15 mmol/L
K+ 150 mmol/L
Cl- 9 mmol/L
Are there more sodium ions inside of outside the cell?
There are more sodium ions outside the cell
Are there more potassium ions inside or outside the cell?
There a more potassium ions inside the cell
Are there more chlorine ions inside or outside the cell?
There are more chlorine ions outside the cell
What is the most dominant extracellular ion?
Sodium (Na+)
What do sodium ions do?
Create osmotic pressure - sodium draws more water in, volume of blood and pressure of blood goes up
What is the normal plasma range for sodium ions?
0.5g or 135-145mmol/L
What are sodium ions needed for?
Nerve conduction (excited nerve cell, na+ rushes in, allows electrical impulses to travel through)
Propagation of action potential
What controls the amount of sodium?
Atrial Natriuretic Peptide (ANP) and Aldosterone
(opposte of each other)
What does Atrial Natriuretic Peptide (ANP) do?
Causes kidneys to lose more sodium
What does aldosterone do?
Steroid hormone
Similar structure to testosterone
Makes kidneys reabsorb sodium
What is hypernatraemia and what are the symptoms?
Too much sodium
Caused by high dietary na+ or infusion of hypertonis saline or water loss or over secretion of aldosterone
Symptoms: thirst, fever, convulsions, raised BP?
What is hyponatraemia and what are the symptoms?
Too little sodium
Caused by inadequate intake of Na+ or vomitting or diarrhoea or burns
Symptoms: lethargy, confusion, reduced BP
What are potassium ions used for?
Nerve conduction - returning cell to its resting state after excitation
Muscles, excitatable cells e.g. neurons
What is the normal serum range of potassium ions?
3.5-5.0mmol/L
What is hyperkalaemia and are the symptoms?
Too much potassium
>5mmol/L
Due to increased renal excretion or burns or cell trauma
Symptoms: irritability, muscle weakness - extreme cardiac arrest
What is hypokalaemia and are the symptoms?
Too little potassium
<3.5mmol/L
Symptoms: abnormal ECG, bradycardia, muscle cramps, decreased tone in muscles
How long does stored blood last and why?
21-35 days as K+ leakage - plasma becomes hyperkalaemic, as red blood cells have no nucleus they can’t repair themselves
Due to improved cyropreservation now 10yrs
What is the normal plasma concentration of calcium ions?
9.4mg/100mL
What are calcium ions required for?
Healthy bones and teeth and nerve excitability
What controls calcium ion levels?
Pathyroid hormone increases levels
Calcitonin decreases levels
What is hypercalcaemia and what are the symptoms?
Too much calcium
Due to excess parathyroid hormone
Causes fatigue and weakness
What is hypocalcaemia and what are the symptoms?
Too little calcium
Caused by vitamin D deficiency
Symptoms: muscle cramps - neuromuscular excitability
Name some other electrolytes and their uses in the body?
Magnesium (Mg 2+) affects other ions
Chloride (Cl -) balancing HCL in stomach
Bicarbonae (HCO 3-) acid/base balance
Phosphorus (Phosphate PO4 3-) works like calcium, bones and teeth
What can cause electrolyte imbalance?
Drud treatments e.g. diuretics effects K+ levels
Patient dependent e.g. on diet
What would you do for electrolyte overdose?
Cation exchange resins promote the body to excrete excess electroyltes
How do electrolytes get into and out of the cell?
Plasma membranes
How does the plasma membrane help maintain homeostasis of the cell?
Defines cell boundaries
Controls interactions with other cells
Regulates what goes in and out of cell (selective permeability)
What is the structure of the cell membrane?
Fluid mosaic - proteins (and carbohydrates) sandwiched between two layers of phopholipid in an oily film
What is the membrane made up of?
90-99% Lipids
1-10% Proteins (these are heavier and account for half of weight)
What is a phopholipid bilayer?
Hydrophilic heads outside
Hydrophobic tails in the centre
(think washing hair not washing feet)
Cholesterol makes membrance “fluid” (if cholesterol level is low membrane goes more rigid)
Where are the membrane proteins found?
Across the plasma membrane
OR
Adhered to the intracellular surface
What do membrane proteins do?
Cell identity markers (antigens which identify cell as being one of yours)
Receptors
Channels, carriers and pumps
Cell-adhesion molecules
Enzymes
Are channel proteins always open?
Some are and they allow water and hydrophilic solutes to diffuse in and out of the cells
Others are always closed and only open when chemical messengers bind to them, this causes the voltage to change across the membrane mechanically stretching it. They control passage of electrolytes, this is important in nerve signals and muscle contractions
What are carriers?
Bind to solutes and transfer them across the membrane
Those using ATP are called PUMPS (against concentration gradient)
Balancing role (down conc gradient = no energy required, up conc gradient =energy required)
Desribe carrier mediated transport?
Proteins in the cell membrane carry solutes through it
It’s either passive (facilitated diffusion down concentration gradient)
Or active (energy requiring)
Solute binds to specific receptor on carrier
Carrier can get saturated
Is facilitated diffusion passive or active?
Passive
Does facilitated diffusion go up or down concentration gradient?
Down concentration gradient, with a carier, does not require energy
Describe facilitated diffusion?
Solute binds to carrier
Carrier changes shape
Carrier releases solute on other side
e.g. glucose
Does active transport go up or down concentration gradient?
Up conc gradient, carrier requires ATP
Describe active transport?
Substance binds to carrier
ATP phosphorlates carrier
Carrier changes shape
Carrier releases substance
e.g. sodium-potassium pump which pumps sodium out and potassium in
What is the purpose of sodium-potassium pump?
Pump sodium out, potassium in
Regulates cell volume
Maintains membrane potential
What is exocytosis?
Eliminating or secreting material from cell (insulin can be released this way)
What is Na+ used for?
Osmotic balance
Body fluid volume
Nerve conduction
Acid-base balance
What is Cl- used for?
Essential for gastric acid production
Balancing ion
What is PO4 - used for?
Acid-base balance
Bone formation
Metabolism of carbohydrates
Found in DNA
What is Ca 2+ used for?
Bone formation
Muscle contraction
Blood clotting
Nerve impulses
What is K+ used for?
Nerve conduction
High conc inside cell
Carbohydrate conversion into energy
