Channels and Transporters Flashcards
What does microscopic current measure?
1 channel
What does Macroscopic current measure?
the sum of all the channels
how do you measure just the K+ channel without measuring the Na+ channel?
block the Na+ channel by adding TTX (tetrodatoxiN)
how do you measure just the Na+ channel without measuring the K+ channel?
block the potasaIUM channel by adding TEA (tetra ethyl ammonIUM)
what are 3 characteristics of voltage gated channels?
they are all or none ( wither closed or open)
they open and close randomly ( stochastically)
if you change the voltage you can increase/decrease the probability that the channels will be open/close
what happens to current as depolarization increases?
there is a larger inward current
what does the patch clamp technique record?
microscopic currents
what did the patch clamp technique provide the first evidence of?
single channels
what is gating?
the transition between open and closed states ( a jump in current)
it involves temporary conformational change in the channel’s structure
depolarization increases the probability that which channel will be open?
Na+ channel ( see pg. 115)
Why do K+ channels have a sustained response i.e. greater maintenance of outward current compared to Na+’s rapid inward current?
because the K+ gate usually can only close it can’t inactivate like Na+ can and closing takes longer to happen whereas inactivation is quick. thus K+ generally doesn’t induce a refractory period like Na+.
are the properties of the microscopic currents the same or different than the macroscopic currents?
they are the same
what produces the diversity in the spike waveforms and patterns exhibited by different cells?
the diversity of K+ channels: some inactivate, some inactivate quickly, some don’t inactivate
how do BK channels inactivate?
rapidly ( BK is fast like burger king)
BK is activated by?
calcium and depolarization
how do medium after hyperolarization K+ channels (AHP) work?
they control the early interspike interval ( they are slowly activating by Ca2+ entry.
***they don’t inactivate
how do slow after hyperolarization K+ channels (AHP) work?
they limit firing frequency by an unknown channel, which affects the action potential
***they do not inactivate
which channel only allows through a single type of ion through the channel ( generally speaking , b/c there are some exceptions)?
voltage gated channels
what type of chanel often lets through two or more types of ions through a channel?
ligand gated ion channels
Why is there so much diversity in K+ channels?
because there are hundreds of genes encoding K+ channels and the splicing variations produce different characteristics in the channels ALTHOUGH most ion channels don’t vary much in fnc.
which K+ channel plays a tumorigenic role in human mammary cells?
Kv4.1 ( it is voltage gated)
Where is Kv1.4 prominent?
in the medial perforate path in the middle molecular layer of the DENTATE GYRUS, and mossy fiber axons and terminals of the S.LUCIDUM of CA-3
Where is Kv2.1 prominent?
PYRAMIDAL cell CA-1 layer
What do Kv2.1 do and what type of inactivation do they exhibit?
they are related to channels involved in repolarization and they show little inactivation.
what do Kv4.1 channels do?
they inactivate rapidly to depolarize.
K+ inward rectifying channels allow more current do flow during?
hyperpolarization than during depolarization
4 channels together can make a _______ ________?
passive pore
what component of an ion channel can impart voltage sensitivity to close or open a channel?
the transmembrane alpha helix loop
what is a channelopathy?
a genetic disease resulting in a mutation in channel genes.
what are some voltage gated Calcium channelopathies?
congenital stationary night blindness
familial hemiplegic migrane ( x-lined recessive)
episodic ataxia type 2
what are doe Na+ channelopathies?
generalized epilepsy w/ febrile seizures
What are some K+ channel channelopathies?
Benign familial neonatal convulsion
How does the structure of K+ compare to that of Ca2+ and Na+?
it is a 5-7 transmembrane domains whereas Ca2+ and Na+ have many more.
what does Saxitoxin do?
like TTX it blocks Na+
what does alpha toxin do?
prolong the duration of Na+ currents
what does beta toxin do?
shift the voltage activation of Na+ channels
what does Batrachotoxin do?
inactivate Na+ channels
what does Dendrotoxin do and where is it found?
block K+ channels , it’s found in wasps
what does Apamin do and where is it found?
It blocks K+ channels and is found in bees.
what do ion exchangers use for energy?
concentration gradients NOT ATP
Is ion translocation slower or faster in transporters than it is in channels?
slower in transporters than in channels
