A cell has a resting membrane potential of -66 mV and a membrane Cl ion equilibrium potential of -24.0 mV
If a neurotransmitter acts on the cell membrane to open channels that are specifically permeable to Cl, will the membrane potential of the cells change? In which direction?
I'm not sure:
This could mean that the Cl ion permeability is increasing. If so, by the Goldman equation, the overall membrane potential will move towards the Cl ion equilibrium potential. The membrane potential would become less negative.
Or this could mean that the Cl ion becomes unregulated. If so, then Cl would be removed from the Goldman equation and the membrane potential would move away from the Cl ion equilibrium potential. The membrane potential would become more negative.
Please help. Thanks!
To answer this question, we need to consider the relationship between the resting membrane potential, the Cl ion equilibrium potential, and the action of the neurotransmitter.
The resting membrane potential represents the electrical charge difference across the cell membrane when the cell is at rest. In this case, the resting membrane potential is -66 mV.
The Cl ion equilibrium potential is the electrical potential at which there is no net movement of Cl ions across the cell membrane. In this case, the Cl ion equilibrium potential is -24.0 mV.
Now, if a neurotransmitter acts on the cell membrane to open channels that are specifically permeable to Cl ions, there are two possibilities:
1. If the Cl ion permeability increases: This would mean that more Cl ions can flow freely into or out of the cell. According to the Goldman equation, which takes into account the permeabilities and concentrations of ions, an increase in Cl ion permeability would cause the membrane potential to move closer to the Cl ion equilibrium potential. In this case, because the Cl ion equilibrium potential is less negative (-24.0 mV) than the resting membrane potential (-66 mV), the membrane potential of the cell would become less negative.
2. If the Cl ion regulation is disrupted: This would mean that the Cl ion does not follow the normal rules of ion movement, and its behavior is not accounted for by the Goldman equation. In this case, the effect on the membrane potential is uncertain and would depend on other factors influencing ion movement.
To summarize, if the neurotransmitter increases the Cl ion permeability, the membrane potential of the cell would become less negative, moving towards the Cl ion equilibrium potential. If the neurotransmitter disrupts the regulation of Cl ions, the effect on membrane potential is uncertain and would depend on other factors.