Starting at 9 A.M. you hike for 3 hours at an average speed of 5 mph. You stop for lunch from noon until 3 P.M. What is your average speed over the interval from 9 A.M to 3 P.M.?
<u>Neurons</u>, the main cells of the nervous system, <u>have a charged cellular membrane</u>.
Neurons communicate with each other by the transmission (sending and receiving) of electric signals called action potentials.
When a neuron is not communicating, we say it's at rest. <u>The resting membrane potential of neurons is negative on the inside</u>.
When neurons communicate, their membranes' charges change in response to external molecules. For this to happen, a neuron's membrane has "gates" to allow charged molecules (ions) enter and exit the cell. These gates are called ion channels.
<u>When positively charged ions enter the cell, depolarization happens</u>, decreasing the difference in voltage between the inside and outside of the cell membrane; the interior becomes less negative. This is how action potentials are generated.
For an action potential to happen, a neuron most receive a stimulus that starts depolarization of its membrane, once a specific threshold is reached (enough positive ions have entered), then there's no turning point and an action potential is generated, causing depolarization of the membrane. Then positive ions start leaving the cell causing a repolarization of its membrane, before it goes back to resting potential.
When negatively charged ions enter the cell, hyperpolarization happens, increasing the difference in voltage between the inside and outside of the cell membrane; the interior becomes even more negative than at resting potential.
Chloride is a negatively charged ion, so when it enters a neuron via its chloride channels, the membrane potential will become more negative than when it was at rest, causing hyperpolarization of the membrane.
The consequence of this hyperpolarization is inhibition of action potential generation, which means that the neuron can't communicate. This is because the inside of the cell is too negatively charged for it to be able to easily reach the action potential threshold.
