Lecture 2 (Revised) Flashcards
Only small and lipophilic molecules can cross?
Plasma membrane readily (Ions and larger polar molecules need help to cross membrane)
4 Types of Ions Channels?
1) Leak
2) Stretch-activated
3) Ligand-gated
4) Voltage-gated
1) (Ion Channel) Leak?
Constitutively active channels
2) (Ion Channel) Stretch-activated?
When plasma membrane is stretched, channel is activated
3) (Ion Channel) Ligand-gated?
A molecule (ex. neurotransmitter) binds to the protein to activate a channel
4) (Ion Channel) Voltage-gated?
Channel activates following a change in membrane potential
Action Potential?
Transient changes in membrane potential caused by orchestrated opening and closing of ion channels
(AP) From - to +?
Depolarization
(AP) From + to -?
Repolarization
When it repolarizes and it goes past -70 mV, that is?
Hyperpolarization
Resting Potential of AP?
-70 mV
Membrane Potential?
(Em)
-Voltage difference across lipid bilayer
-Created by varying concentrations of ions on either side of plasma membrane
What is the charge at a specific moment?
Membrane Potential (Em)
Equilibrium (Nernst) Potential?
(Eeq)
Reflects a balance (at equilibrium) between chemical and electrical gradients for a single permeable ion
Equilibrium (Nernst) Potential Equation?
Eeq = 58/z * log (Co/Ci)
(z = ion charge)
(Ci = internal conc.)
(Co = external conc.)
Direction of Ion Movement?
Determined by knowing Equilibrium and Membrane Potential for that ion
(Membrane Potential will always wants to go towards Equilibrium)
Membrane Potential will always want to go towards?
Equilibrium
(Cation (+))
Em < Eeq?
Moves IN
(Cation (+))
Em > Eeq?
Moves OUT
(Anion (-))
Em < Eeq?
Moves OUT
(Anion (-))
Em > Eeq?
Moves IN
Ena?
+67 mV
Ecl?
-33 mV
Ek?
-84 mV
Goldman Equation describes?
Resting membrane potential, accounting for relative permeabilities, and concentration gradients of 3 primary permeable ions
Goldman Equation?
(Goldman Equation)
Can change resting membrane potential (Em) of a cell by?
1) Changing relative permeability of a specific ion (primarily by K+)
2) Concentration of an internal/external concentration
1) (Goldman Equation) (Em shifts with changing [K+])
As external [K+] increases, Em becomes?
Less negative (depolarization)
1) (Goldman Equation) (Em shifts with changing [K+])
As external [K+] decreases, Em becomes?
More negative (hyperpolarization)
2) (Goldman Equation)
Em shifts with changes in relative permeability?
Em moves toward equilibrium potential of ion of increased permeability
