the membrane potential became less negative because less potassium ions went out of the cell (since the extra cellular space has higher concentration of potassium, and potassium goes down its concentration gradient, from high concentration to low concentration). since less potassium (K+)which is positive, left the cell more it became more positive (less negative)
Slightly permeable to sodium ions.
sodium/potassium pump
Hyperpolarization means that the membrane potential becames more negative than the resting potential. This means that it is more difficult for an action potential to be triggered at the postsynaptic membrane. This occurs at inhibitory synapses. Hyperpolarization can be achieved by increasing the permeability of the membrane to potassium or chloride ions. If potassium permeability is increased more potassium ions will leave the cell, down their concentration gradient; if chloride permeability increases chloride ions will enter the cell down their concentration gradient. Both movements will make the inside of the cell more negative ie they will cause hyperpolarization.
The relative concentration of sodium (Na+) and potassium (K+) in the neuron with respect to their concentration in the extracellular space is what causes the electrical potential and the differential concentration is established by a Na-K Atpase which exudes sodium and transports potassium into the neuron.
During depolarization, sodium (Na) rushes into the neuron through Na channels (at the Nodes of Ranvier between the bundles of myelin "insulation"). Less Na in the extracellular fluid would mean there would be less to rush in. So, the neuron would not be depolarized as well. The resting membrane potential would be more positive on the inside.
sodium-potassium
Not much. Changing the extracellular chloride changes the level inside the cell so they will be in equilibrium again. The chloride ion plays little role in resting potential.
...repolarization
The resting membrane potential is the difference between the inside of the cell relative to the outside. The outside is always taken as 0mv. The resting membrane potential is negative because there is a higher concentration of potassium ions outside the cell (because the membrane is more permeable to potassium ions) than inside. Since potassium ions are positively charged this leads to a negative value.
A potassium enhanced intravenous solution would increase the concentration of potassium ions in the brain. Since potassium ions are positively charged, they depolarize the resting membrane potential. For example, a resting membrane potential of -65 millivolts would be depolarized to -62 millivolts. An appropriate concentration could lead to a significant depolarization of, say, -60 millivolts, at which point an action potential could be possible.
Equilibrium potential is referring to the equilibrium (or balance) established between the forces of diffusion and electrical forces specific to each ion. For example, the equilibrium potential for Potassium, K+, in a cell with a semi permeable membrane is -80mV or Ek+=80mV. The membrane potential, on the other hand, refers to the voltage across the membrane at anytime and takes into account a range of equilibrium potentials such as Potassium, Sodium etc.
It makes the inside of the neurons more negative.