Nerons

Neurons exhibit a resting potential which arises from the difference in ion concentrations between the inside and the outside of the neuron (Bond and McConkey, 2001). In other words, when the neuron is not firing, the inside of the cell is negative with respect to the outside and thus there exists a voltage difference (Gleitman, 1999). In order for the neuron to fire, a stimulus must act upon it that is large enough to reduce the voltage difference to the excitation threshold (Gleitman, 1999). If the stimulus is large enough, then the voltage difference collapses rapidly to zero and then begins to reverse itself, with the inside of the neuron becoming more positive (Bond

Ion channels are highly selective, only allowing the passing of certain ions in and out of the neuron (Kendel et al, 1995). Many models have been proposed to explain this selectivity, but the most highly supported theory is that of a selectivity filter (Kendel et al, 1995) (see figure 2). As the selected ion moves through the filter it binds to an active site. Because it is hydrophilic, the ion has a cloud of water molecules surrounding it. When it binds to an active site, the ion sheds most of its waters and in their place forms weak chemical bonds with charged amino acid residues that line the walls of the channel. An ion will move along the channel only if the energy of interaction with the selectivity filter compensates for the loss of waters. Since different ions have different sized clouds of water molecules surrounding them, the filter ensures that only certain types of ions pass through the channel (Kendel et al, 1995). Ultimately, the filter is discriminating between the ions on the basis of their ionic charge (Kendel at al, 1995).

and McConkey, 2001). This occurs because of the passage of charged ions into and out of the neuron (Gleitman, 1999)

Ions are molecules or single atoms which have lost or gained electrons and therefore posses a positive or negative electrical charge (Gleitman, 1999). In its resting state a neuron contains a high concentration of potassium ions dissolved in the fluid inside its membrane, and a high concentration of sodium ions dissolved in the fluid outside (Gleitman, 1999). When the excitation threshold is reached,

Some topics in this essay:
Bond McConkey, ATP Kendel, , al 1995, et al 1995, et al, ion channels, kendel et, gleitman 1999, kendel et al, bond mcconkey 2001, mcconkey 2001, bond mcconkey, sodium ions, nervous system, movement ions, al 1995 pump, neuron bond mcconkey,