Lecture 9 and 10 Ion equilibrium

Question 1

Electrolyte movement is in response to what 2 things?

Answer 1

Concentration gradient
Electromotive forces (EMF)

Question 2

Is the capacity to do work. Therefore, it refers to electric charge difference between two compartments. ALWAYS.

Answer 2

Electric potential

Question 3

Vm=Transmembrane voltage

Answer 3

Vm always refers to the inside versus the outside. i.e. if there is a more positive charge on the inside, Vm will be positive.

Question 4

Nernst equation

Answer 4

Where,
Eion=equilibrium potential for given ion
z=electric charge of ion (e.g.. +1 for K+, -1 for Cl-, +2 for Ca2+)
This holds for 37°C

Question 5

For K+ =-88mV  which way would K+ move if
Vm=
0
-87
-88
-89

Answer 5

Out
Out
No movement
In

Question 6

Eion equilibrium potential of 
K+
Na+
Ca2+
Cl-

Answer 6

K+ = -88mV
Na+ = +60mV
Ca2+ = +107mV
Cl- = -63mV

Question 7

People with cardiovascular disease also suffer from what?

Answer 7

Hypokalemia
(A common reason is use of diuretics in patients with hypertension. (In the renal lectures the reason why diuretics can effect K+ levels in the plasma will become clear.)
Hypokalemia increases mortality of patients with cardiovascular disease by 10-fold.
It induces arrhythmia by modifying equilibrium potential. )

Question 8

Why is Resting Potential of Most Cells ~ -70mV?

Answer 8

• Cells are permeable, to differing degrees, to multiple ions. The resting potential (-70mV) is a weighted mixture of EK+ (-88mV), ECl-(-63mV), ENa+(+60mV) and their respective conductance.
• Permeability of cells is highest for K+. Thus resting potential near the K+ equilibrium potential.

Question 9

How Does Vm Change and Why is that of Importance in Physiology?

Answer 9

Permeability change is a fundamental aspect of cell function.
Ex. beta cell at rest when glucose is low in blood. secretes insulin when glucose is high in blood.

Question 10

What would happen to a cell’s transmembrane potential if Pna↑? Permeability of na increase

Answer 10

It will depolarize

Question 11

(skeletal muscle Na+channel mutation). Incidence: 1/100000.

Answer 11

Periodic paralysis

Question 12

hypermetabolic state triggered by anethetics (Ca2+ channel mutation). 1/3000 to 1/50000 anesthesia depending on population examined

Answer 12

Malignant hyperprexia

Question 13

exocrine function of epithelial cell is aberrant (thick mucous produced in lungs for example) due to defective Cl- channels. Prevalence: 1/2500 newborns.

Answer 13

Cystic fibrosis

Question 14

caused by mutation in one of the Na+ channel. Prevalence: 1/30,000

Answer 14

Seizures