Animal Physiology - The Nervous System - To understand Resting and Action Potential

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Animal Physiology

The Nervous System

AIM: To understand Resting and Action Potential

        All living cells have electrical differences across the membrane this is called the membrane potential and is defined as the electrical potential measured from within the cell relative to the potential of the extracellular  fluid.

        Only some cells (neurones and muscle)have the ability to change the membrane potential and are known as Excitable cells.

        Neurone signals start as a change in the electrical gradient across the membrane , the signal is then transmitted along the length of the neuron to the axon tip.

        The gradient depends on the ion flow across the membrane (The ions move through ion channels in the membrane)

        An unexcited neurone is at its resting state - refer to figures 21,22 booklet 1. Figure 22 shows that the invertebrates may have large neurones as in the giant squid, they are good model systems.

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NB: The electrical currents of membrane potentials are formed from the net flux of charged particles that move across the membrane.

Resting Membrane Potentials (RMP)

        The RMP arises as a small build up of negative charges forming just inside the neurone, there is also an EQUAL build up of positive charges on the outside of the neurone.

        The RMP is measured in millivolts (mV) and typically lies between -40 and -90 mV.

        The RMP arises from differences in the ion concentrations between the cell (neurone) and the extracellular fluid.

Outside the cell = ,

Inside the cell =


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