NERVE IMPULSES
An impulse begins in the nucleus of the neuron or cell with the movement of electrically charged inorganic molecules through the cell’s membrane.
This membrane is semi-permeable. It allows some charged molecules, known as ions, to pass more easily than others.
Potassium (K+), positive charge, is the most prominent ion that passes easily through a neural membrane in its resting state.
The resting potential in its base state is about a minus 70 mV relative to the outside. An equilibrium will result from the distribution of these ions on either side of the membrane.
The passage of a nerve impulse changes the equilibrium. Sodium (Na+), positive charge, and chloride (Cl-), negative charge, have more difficulty passing through.
Large, negatively charged molecules inside the cell cannot get out but do influence the membrane’s electrical potential.
The calcium ion (Ca++) plays also an important role in the chemical process of synaptic transmission.
