Lec 4 Flashcards
Where are post-synaptic potentials integrated
At the axon hillock
Squid Giant axon
The size of the giant axon allowed the use of microelectrodes to be used effectively to stimulate and record
What would stimulating an axon do?
Release an action potential
What is important for the peak of an action potential
Sodium levels
Phase 1 of an action potential
Depolarization
Phase 2 of an action potential
Repolarization
Phase 3 of an action potential
Hyperpolarization
Increased permeability to what during the rising phase
Sodium
Increased permeability to what during falling phase
Potassium
absolute refractory period
Cell is incapable of generating a new action potential
Relative refractory period
More difficult to generate a new action potential
Voltage Clamp experiments found
Early inward Na+ current followed by later outward K+ current
What blocks the outward K+ current
Tetraethylammonium (TEA)
What blocks the inward Na+ current
Tetrodotoxin (TTX) and Saxitoxin (STX)
Structure of the Na+ channel
-Consists of an alpha and 2 beta subunits
alpha has 4 separate domains (D1-DIV)
Each domain has 6 helical segments (S1-S6)
S4 is charged, and is the voltage sensor to open the activation gate
IFM-the inactivation gate
Structure of the Ca+ channel
1 alpha and 2 beta subunits
alpha has 4 separate domains (D1-DIV)
Each domain has 6 helical segments (S1-S6)
S4 is charged, and is the voltage sensor to open the activation gate
IFM-the inactivation gate
K+ channel structure
1 alpha and 2 beta subunits
alpha has 4 separate domains (D1-DIV)
Each domain has 6 helical segments (S1-S6)
S4 is charged, and is the voltage sensor to open the activation gate
IFM-the inactivation gate
All four domains are identical
VSD-Voltage sensitive domain
S1-S4
P-Loop
Between S5 and S6
Determine ion selectivity
Pore domain
S5,S6
Where is the IFM
After S6 (last part)
What kind of changes do ion channels undergo when channels are opening, closing and inavtivating
Conformational changes
