4/ the excitable cell Flashcards
1
Q
nerve signal speed
A
15 m/s
2
Q
action potentials vs graded potentials
A
- AP: fixed size, all or nothing, propagate along axon. tend to pass one way along axon. coded by frequency (same size)
- graded potential: variable size, local signals not propagated along long distances. pass both ways along axon. coded by size
3
Q
how to measure membrane potential in a neuron
A
- connect neuron to voltmeter by inserting glass microelectrodes into neuron (KCL) and solution (silver chloride)
- no potential difference in extracellular solution
4
Q
what is the resting membrane potential of neurons
A
- all between -40 to -80 mv
- most -60 to -70 mv
5
Q
3 reasons neurons have a resting potential
A
- selectively permeable membrane
- unequal distribution of ions
- physical forces
6
Q
2 most important ion pumps
A
- sodium potassium ATPase (70% of brain ATP on this)
- calcium pumps (not just in plasma membrane). important since calcium is a signalling molecule and is toxic in high intracellular conc
7
Q
what is conductance
A
- symbol is G
- G = 1/R
- how easily current travels through a neuron
8
Q
What is Eion?
A
- membrane potential achieved in a neuron is the memb were selectively permeable to that ion
9
Q
when is equilibrium achieved
A
- electrostatic forces = diffusional forces
- Vm = Eion
- electrical forces bringing potassium into the cell are the same as the diffusional forces pushing them out
10
Q
nerst equation
A
- Eion/equilibrium potential of an ion =
- 2.303 X
- RT/zF X
- log (ion conc outside/ion conc inside)
- R = universal gas constant, T = temp, z = charge (eg potassium +1, sodium -1), F = faraday constant
11
Q
intracellular and extracellular concentrations of K+, Na+, Ca2+, Cl- in mM
A
- K+: 100/5
- Na+: 15/150
- Ca2+: 0.0002/2
- Cl-: 13/150
12
Q
goldman equation
A
on flashcard
