Excitable Cells- Lecture 1 Reiser Flashcards
3 types of channels
- ligand sensitive (chemically regulated)
- voltage sensitive
- mechanosensitive
the membrane resting potential is most permeable to…
K+
the Pk/Pna ratio at the resting membrane potential is
~60
The resting membrane is slightly permeable to Na, therefore Na diffuses into the cell down both of its… amd… and this is what keeps the resting membrane potential slightly lower than Ek
concentration and electrical gradient
change of the membrane toward 0 mV is referred to as
depolarization
change in membrane potential away from 0 mV in the negative voltage direction is referred to as
repolarization
an increase in potential from the resting value (more negative) is reffered to as
hyperpolarization
the peak of the AP (~40mV) approaches the …
equilibrium potential for Na+ (~58mV)
axons with large diameters have …. conduction velocities
higher
are the Na and K channels at the motor endplate chemically or voltage gated
chemically
end plate potentials: are they spontaneous?
no
EPPs occur after
an AP in a motorneuron
what is the amplitude of an EPP
10mV
EPPs are confined to the
end plate region
Miniature EPPs occur at…
rest
MEPPs: spontaneous or no?
spontaneous
MEPPs are confined to the
end plate region
MEPPs follow the release of the contents of
one synaptic vesicle
MEPP amplitude?
1-2 mV
role of acetylcholinesterase is to breakdown… into which two products?
- acetylcholine
- acetic acid (acetate) and choline
Breakdown of acetylcholine: Acetate enters the… and choline is taken up by the …. where it reacts with…., by the action of…. to form….
- circulation
- presynaptic terminal
- acetyl-CoA
- choline acetyltransferase
- acetylcholine
Curare ( a plant derivative) binds to … so … cannot bind. As a result Ach will still be released at the presynaptic terminal but no APs will occur
acetylcholine receptor
ACh
Botulinum toxin blocks… so skeletal muscle activation cannot occur
ach release
Organophosphates block action of …. so ach cannot be hydrolyzed; cannot activate skeletal muscle in its presence because Na channels remain in refractory state
acetylcholinesterase