Ion Channels and Ion Pumps

Signaling in the brain depends on the rapid response of neurons to changes in stimuli. These rapid responses are due to the presence of ion channels in the nerve cell membrane. Each ion channel is primed to respond to specific stimuli, either chemical or physical. They also have the property of heterogeneity: there are different types of channels in different parts of the nervous system, each one specific in what kind of ion they transport across the nerve cell membrane.

 

In addition to these ion channels, nerve cells also sport ion pumps/transporters. These pumps do NOT contribute to rapid signaling, but are more important for establishing and maintaining ion concentration gradients. Ion channels, on the other hand, are limited to the passive transport of ions down their concentration and electrical gradients.

Therefore, two main differences between ion channels and ion pumps are that ion pumps regulate active transport of ions, which makes sense considering they transport ion against their concentration gradients. This active transport utilizes ATP (incidentally, the brain uses about 20% of the body’s total energy; much of this 20% is due to the maintenance of the ion concentration gradients via ion pumps).

Another difference between ion pumps and ion channels is that the ion channels have a water-filled pathway through which ions flow from one side of the membrane to the other. Ion pumps, on the other hand, transport ions by undergoing conformational changes.

 

 

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