Lec 29 Flashcards
Action potential is
The voltage across a membrane
Resting membrane
-70mV
Negative inside
Ions important for action potential
Na+ and K+
Cl-
Resting is maintained by
Sodium potassium pumps (3 sodium out, 2 potassium in )
Potassium leak channel (open randomly allowing potassium to leave)
Ion channel shape
Channel
Potassium channels are
Homotetramers
4 subunits with a pore in the middle
Sodium channels are
Monomers with 4 domains
Sodium and potassium channels classification
Passive
Uniport
Gated
Both channels are
Voltage gated
When the potential is -40mV, they open
Has winglike channels keeping it closed that open when the inside is more positive than the outside
Sodium channels open
Quicker
Sodium channels are also
Channel inactivated
Can either be open or inactive (protein that wants to move negative charge in the outside blocks the channel)
Potassium are only
Voltage gated
Open or closed
Na + channels go from
Closed to open to inactive and then back to closed
Voltage gated channels allow for the transport of
Many ions
Pumps and channels only allow few
Depolarizing phase
Once membrane potential passes -40 mV, all Na+ channels open
Goes to +40 mV
Repolarizing phase
Na+ channels inactivate
K+ channels open
Which drives the membrane potential back down
Refractory period
Na+ channels inactive
K+ channels open
Ready for new action potential
After membrane is below -40mV for a time
Na+ and K+ channels close
How a action potential travels in a typical neuron
Many action potentials happen along the axon in a localized region
They spread along the axon
Action potential speed
5 m/sec
Does the action potential lose strength as it travels
No
Injecting Na+ into the middle of the axon
An action potential would travel in both directions
Giant axons
Found in invertebrates
Larger diameter leads to quicker action potentials
Vertebrate method of speeding up action potentials
Glial cells wrap a neuron with myelin
Action potential hops between gaps
