Module 3: Lecture 1 Flashcards
Can ions travel across the lipid membrane? why or why not?
- they cannot
- they are very water-soluble
What does it mean when a membrane has been polarized?
there’s a separation of charge across that membrane
The separation of charges can create what?
membrane potential
True or False
the plasma membrane of all living cells are polarized electrically?
true
At rest how do we restrict the movement of ions?
with the plasma membrane
What is the fundamental basis that allows your nervous system to communicate?
separation of charge
What are the 5 key factors regarding membrane potential?
- There is a separation of charges across a membrane
- Theres a difference in concentration of cations and anion in the intracellular fluid and extracellular fluid
- There’s a difference in permeability of key ions
- There’s ion movement and membrane potential due to the difference in concentrations
- Membrane potential is measure as Volts or millivolts
What are 2 factors we need to take into consideration when ions cross a membrane?
- What are the driving forces
- is sed ion actually able to cross the membrane
What way do ions move in a concentration gradient?
from high to low
What way do ions move in an electrical gradient?
- opposites attract
- like charges repulse
What types of gradients do we need for ions to move across a membrane?
- concentration gradient
- electrical gradient
The combination of the concentration and electrical gradient gives us what?
electrochemical gradient
Can there be membrane potential with equal charges on both sides?
naurr
- the potential comes from a difference in charges in the ICF and ECF
What does electrical neutrality mean?
- equal number of neg and pos charges on both sides
- no potential
Where does the separation of charged occur in a cell?
ions are located in a thin layer along the outer and inner surface of the membrane
- the rest of the fluid either ICF OR ECF will be electrically neutral
What are non-excitable cells and excitable cells?
cells that have a resting membrane potential that is relatively constant
What are excitable cells?
- nerve cells or muscle cells
- produce rapid and transient changes in their resting membrane potential when excited
- aka electrical signals as communication
What are the concentrations of ions of a resting nerve cell
in reference to the chart (Na+, K+ and A-)
Na+
- extracellular = 150
- intracellular = 15
- relative permeability = 1
K+
- extracellular = 5
- intracellular = 150
- relative permeability = 50-75
A-
- extracellular = 0
- intracellular = 65
- relative permeability = 0
Which ion is more permeable at rest Na+ or K+
K+
Na+ and K+ are water soluble so how do they pass through the membrane?
passively through protein channels / leak channels
Given a cell with highly concentrated Potassium in the ICF what forces are acting on the potassium?
- Concentration gradient will allow potassium from the ICF to traverse to the ECF along it’s concentration gradient through protein channels
- Eventually the ICF will be more neg as it is losing it’s pos charges of K+ and the ECF will be more pos as it’s gaining K+, therefore an electrical gradient will from and want the potassium to be pushed back into the cell through the same leak channels
*eventually equilibrium will be reached as both the concentration gradient and electrical gradient will be equal
What is the equilibrium potential?
when the net movement of ions is 0, equal within forces
ie. concentration gradient and electrical gradient are equal on both sides
What value is the potassium equilibrium potential in neurons?
-90 mV
True or False
Even with an equilibrium potential the concentration gradient can still be larger on one side of the cell?
True
True of False
We always refer to the inside of the cell when talking about values
True
What is the Nernst equation?
E= 61 log Co/Ci
What do the values in the Nernst equation mean?
E = equilibrium constant for the ion in mV
61= constant value
Co = concentration of the ions outside the cell
Ci = concentration of the ions inside the cell
What would the Nernst equation look like in reference to potassium?
E = 61log10 (5mM/150mM)
E = -90mV
What would the Nernst equation look like in reference to sodium?
E = 61log10 (150mM/15mM)
E = +65mV
What value is the sodium equilibrium potential in neurons?
+65 mV
