Active Transport and the Sodium/Potassium Channel Flashcards
What is the intracellular and extracellular concentrations of sodium and potassium?
Na- 140mM out, 10mM in
K- 5mM out, 140mM in
How do we control the electrochemical gradient?
Through Na/KATPase
What is the structure of the sodium pump?
2 alpha subunits with an ATP binding site each
2 beta units with cardiac glycoside binding sites
What is the Km for Na?
20mM
What is the Km for K?
1mM
What limits the activity of the sodium pump?
Decreasing intracellular sodium concentration
Decreasing potassium concentration extracellularly
How many times does the sodium pump go a second?
100
How can you inhibit the sodium pump?
Digoxin binding to cardiac glycosides
What happens when to the dose response curve if you decrease the extracellular concentration of K when digoxin is present?
Moves to the left
What is the therapeutic index?
The difference between the toxic effect and the therapeutic effect
How do you calculate the therapeutic index?
Minimum effective dose for 50% of the population
What do you use remifentanil for and what is its TI?
Patient controlled analgesia during labour
33000:1
What do you sue diazepam for and what is its TI?
Sedative
100:1
What do you use ethanol for and what is its TI?
Sedative
10:1
What do you use digoxin for what is its TI?
Congestive heart failure 2:1
What is the range of hypokalaemia?
Less than 3.5mM
What is the range of normokalaemia?
3.6-5.3 mM
What is the range of hyperkalaemia?
More than 5.5
What are the symptoms of hypokalaemia?
Abnormal heart rhythms
Muscle damage
Muscle weakness or spasms
Paralysis
What are the symptoms of hyperkalaemia?
Nausea
Palpitations
Muscle weakness
Why is potassium level important for giving digoxin
If you are hypokalaemic then you increase the affinity for digoxin
This means you have to take into account the change in concentration as the therapeutic index has now changed as well
What condition will lead to an increase in digoxin binding?
Hypokalaemia
How does a diuretic treat pulmonary oedema?
Increases the volume output of the kidneys meaning there is a pressure that pulls the excess fluid out of the lungs
What does diuretic used for?
High blood pressure
Excessive fluid retention
What are the side effects of diuretics?
Increases urinary excretion of potassium
How are digoxin and diuretics related?
Patients on digoxin who start diuretics may become hypokalaemic
A reduction in competition between K and digoxin results in increased digoxin binding to the sodium pump
Because of the very narrow therapeutic index, the patient develops digoxin toxicity
What do you treat digoxin toxicity with?
Digibind
What are the different concentrations of the sodium calcium exchanger?
Na- 140mM out, 10mM in
Ca- 2mM out
What is the internal voltage inside the cell?
-70mW
What is the function of GLUT1?
Basal uptake in placenta and brain
What is the function of GLUT2?
Trans epithelial transport, Beta cells
What is the function of GLUT3?
Basal uptake in the brain
What is the function of GLUT4?
Skeletal muscle
What is the function of GLUT5?
Intestinal absorption of fructose
Describe intestinal uptake of glucose?
Sodium potassium pump pushes sodium out of the cell
2 sSodium enters through co transported with glucose
