Question

Unmarked drugs are tested on neurons in order to identify them. The conditions of the neuron are that it is only permeable to K, Cl and Na.

1. The first test depolarizes the resting membrane potential from -70mV to -20mV. What are two reasons for this happening?

2. The second test on a new neuron, hyperpolarizes them -70mV to -90mv? What happened?

3. The last test resulted in no effect at first, then the Vm goes to 0mV and remains there. Why does this happen?

Answer 1

The neurons are called in polarized stage when it is in -70mV. In this stage more sodium ions are in the outside of the neurons and potassium and chlorine ions are present inside the neurons. When there a series of depolarisation and repolarisation occurs due to the changes in the ions is called action potential. It leads to close or away from the threshold limit.

1. In the drug test it depolarizes the neurons by changing -70mV to -20mV. There is less negative charged. It occurs due to some voltage-gated ions inflow and outflow. As a result action potential happens and the cyton is more excited as it is charged. The inside of the neuron sodium ions are more and potassium ions start to go outside the membrane to establish depolarization state. The drugs contain Cl and Na which enters into the neuron by voltage gated channels and depolarizes it. In short it leads a excited stage in the neurons.

2. In the second test on a new neuron, the membrane potential becomes -70mV to -90mV. It leads to more negative and hyperpolarised the neuron. Hyperpolarisation is an abnormal condition where it is difficult for a neuron to get back to action potential and repolarizarion stage. It is a serious pathological condition where neuron are not ready to respond any stimuli. In this case the drug may contain more chlorine which increases the negative ions inside the neurons and also facilitate the out flow of potassium in the neurons.

3. In the last test resulted no effect at first, then the mV goes to 0mV and remains there. It is the threshold limit of the membrane potential and somehow the neurons remain the depolarization stage. Then neurons are in threshold point as the ions present in the drugs and the neurons coordinate with each other with some variance level. That's why it is in the 0mV not in -70mV which is resting condition.

From the above experiment it has shown the drug is doing slight or extreme neurological excitements by varying the voltage-gated ions.