HY Step1 Physio Questions

[MudPhud20XX]

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Again, I will start from here.

I always have difficult time with these kind of physio experimental q.

Researcher are studying how the membrane potential of a postsynaptic neuron changes in response to neurotransmitter stimulation. Baseline measurements determine that the membrane is permeable to a particular cellular ion at rest. When stimulation begins, ligand-gated ion channels open (black arrow) and increase the membrane permeability for a different cellular ion. It is found that the resulting change in membrane potential then triggers the opening of voltage-gated ion channels (red arrow), increasing the membrane permeability for a third type of cellular ion. The results of the experiment can be seen in the graph below.

The equilibrium potentials of some important cellular ions include the following:

ENa = +60mV
EK = -80mV
ECl = -90mV
ECa = +125mV

Given this information, match the appropriate neuron's permeability to each cellular ion.

Resting membrane permeability --> ?
Ligand-gated ion channel permeability --> ?
Voltage-gated channel permeability --> ?

 

[gurujolly]

Yeah I had to read it like 3 times, before I got what it was asking for. WTF my head.... kinda reminds me of the AV node current. My intuitive guess was (resting membrane potential:EK-80mv), (Ligand-gated ion channels:ECa=125+mv), (voltage gated channels:ENa=+60mv)

 

[Gdl88]

I'm not sure...resting membrane ECl = -90 mV;ligand gated ENa = 60 mV and voltage gated channels EK=-80 mV.

 

[seminoma]

Again, I will start from here.

I always have difficult time with these kind of physio experimental q.

Researcher are studying how the membrane potential of a postsynaptic neuron changes in response to neurotransmitter stimulation. Baseline measurements determine that the membrane is permeable to a particular cellular ion at rest. When stimulation begins, ligand-gated ion channels open (black arrow) and increase the membrane permeability for a different cellular ion. It is found that the resulting change in membrane potential then triggers the opening of voltage-gated ion channels (red arrow), increasing the membrane permeability for a third type of cellular ion. The results of the experiment can be seen in the graph below.

View attachment 192599

The equilibrium potentials of some important cellular ions include the following:

ENa = +60mV
EK = -80mV
ECl = -90mV
ECa = +125mV

Given this information, match the appropriate neuron's permeability to each cellular ion.

Resting membrane permeability --> ?
Ligand-gated ion channel permeability --> ?
Voltage-gated channel permeability --> ?

I remember this UW question and it's not possible to answer your questions as written. RMP could be chloride or potassium. The Ligand-gated could be either sodium or calcium. And the voltage-gated could be either chloride or potassium.

RMP is negative, hence it has to be one of the ions with a negative equilib potential.
When the ligand-gated channel opens the memb potential becomes more positive, so it has to be one of the ions with a positive equilib potential.
When the voltage-gated channel opens, the memb potential starts going back to RMP, thus it has to be one of the ions with negative equilib potential.