If during an experiment, only potassium channels open on a neuron, what do you expect will happen to the membrane potential? Why?
If only potassium channels open on a neuron, the membrane potential is expected to become more negative. This is because potassium ions (K+) have a higher concentration inside the neuron compared to the extracellular fluid.
To understand why this happens, let's start with the concept of a resting membrane potential. In a resting state, a neuron has a negative charge inside relative to the outside due to the uneven distribution of ions. This is largely maintained by the activity of ion channels, including potassium channels.
Potassium channels are selectively permeable, meaning they allow potassium ions to pass through while restricting other ions. When these channels open, potassium ions freely move across the cell membrane according to their concentration gradient. Since there is a higher concentration of potassium ions inside the cell, they tend to move outwards, leading to an efflux of positively charged K+ ions.
As potassium ions exit the neuron through these open potassium channels, they leave behind negatively charged proteins and other negatively charged molecules inside the cell. This creates an excess of negative charge, resulting in the membrane potential becoming more negative, or hyperpolarized.
In summary, when only potassium channels open on a neuron, the increased efflux of potassium ions leads to a net loss of positive charge, causing the membrane potential to become more negative.