• identify neurones as nerve cells that are the transmitters of signals by electro-chemical changes in their membranes

Signals are transmitted by nerves in the form of electricity along the neurone.

A potential difference exists across every cell’s membrane. The side exposed to the cytoplasm is negative while the side exposed to the extracellular fluid is positive. (i.e. the inside is positive and the outside is negative)

The resting membrane potential is about -70mV, i.e. the inside is negative.

Cell membranes are impermeable to proteins and most organic phosphates, so they are kept in the cytoplasm. However, membranes are selectively permeable to sodium, potassium and chlorine ions because of ion channels, which allows ions from one side of the membrane to move to the other.

Changes in the environment of a neurone can affect the membrane’s permeability to ions and thus the membrane’s potential. Any environmental factor that causes such a change is called a stimulus and neurones are highly reactive to stimuli.

In response to stimulation, a cell’s membrane potential can change. When the inside of a cell (normally negative) experiences a positive shift in membrane potential, it is called depolarisation.

If the depolarisation is strong enough, the flow of ions causes the neurone to generate a nerve impulse/ action potential. These action potentials are transmitted from neurone across small gaps called synapses. The movement of these action potentials are in one direction only.

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not the most coherent summary… but should give a general understanding