Lecture 3- Membrane Physiology 1 Flashcards
What is voltage?
Force motivating electrons to flow
-difference between electrons I two places
What is current?
I - the continuous movement of free electrons through a circuit ‘flow’
What is resistance?
Opposition to movement of electrons(must be between two points)
What is the reciprocal of resistance?
Conductance
What is ohms law?
V=IR
What provides resistance to the flow of ions in a cell system?
Membrane channels
Where is there more Na at rest?
Outside the cell
Where is there more K at rest?
Inside the cell
Where is there more Cl and Ca at test?
Outside the cell
What is the Nerst equation used for?
To calculate the equilibrium potential for any ion in a system
What determines the force moving an ion through the membrane (net driving force)?
Membrane voltage-equilibrium potential for that ion
What ion is the membrane most permeable to?
K
What does g represent?
Conductance of an ion
What is the electrical equivalent of membrane permeability?
Membrane conductance
At rest the drive force of which ion is larger, Na or K?
Na
At rest is the resting membrane potential close to the equilibrium potential for K or Na?
K
What is the function of the Na-K ATPase enzyme?
Uses cellular energy to move 2K into the cell and 3Na out of the cell against their concentration gradients. This is needed to maintain a voltage across the membrane
What is the inhibitor of the Na-K ATPase enzyme?
Ouabain
What are 3 factors that affect the activity of the Na-K pump?
- Ouabain- metabolic inhibitor
- Low temp- decrease activity
- Removal of external K from around the cell will inhibit pump
What is the main cause of the resting membrane potential? What mechanism also contributes?
Main cause- passive loss of K
Contributor- Na removal by pump
What are 2 neurological disorders caused by mutations in the calcium channel?
Familial Hemiplegic Migraine
Congenital Stationary Night Blindness
Why is the cell membrane called a capacitor?
Has capacity to store charge with an insulator (membrane) sandwhiched between two conductors (extracellular fluid and cytoplasm?
What are the 5 gating mechanisms of ion channels?
- Voltage-gated
- Ligand-gated
- Mechanically gated
- Light gated
- Thermogated
What does the gNa tell you?
the Na conductance, i.e.. the # of Na channels
Why is the membrane closer to the equilibrium potential of K rather than Na at rest?
Because of K leak channels, the membrane is 20x more permeable to K than Na
What mechanism counteracts the constant leak of K out of the cell and small amounts of Na into the cell to maintain the resting membrane potential?
Na/K ATPase pumps 3 Na out and K in to the cell to maintain the resting membrane potential along with K leak channels
