21. How much does the charge on a neuron have to decrease in order to get to the threshold level?

A. From -70 mV to -50 mV
B. From -70 mV to -20 mV
C. From -70 mV to neutral



Answer :

To determine how much the charge on a neuron has to decrease to reach different levels, we can follow these steps:

1. From -70 mV to -50 mV:
- Initial charge: -70 mV
- Target charge: -50 mV
- The decrease required can be calculated as: [tex]\(-50 mV - (-70 mV)\)[/tex]
- This simplifies to: [tex]\(-50 + 70 = 20 mV\)[/tex]
- Therefore, the charge must decrease by 20 mV.

2. From -70 mV to -20 mV:
- Initial charge: -70 mV
- Target charge: -20 mV
- The decrease required can be calculated as: [tex]\(-20 mV - (-70 mV)\)[/tex]
- This simplifies to: [tex]\(-20 + 70 = 50 mV\)[/tex]
- Therefore, the charge must decrease by 50 mV.

3. From -70 mV to neutral (0 mV):
- Initial charge: -70 mV
- Target charge: 0 mV (neutral)
- The decrease required can be calculated as: [tex]\(0 mV - (-70 mV)\)[/tex]
- This simplifies to: [tex]\(0 + 70 = 70 mV\)[/tex]
- Therefore, the charge must decrease by 70 mV.

In summary:
- To reach -50 mV, the charge must decrease by 20 mV.
- To reach -20 mV, the charge must decrease by 50 mV.
- To reach neutral (0 mV), the charge must decrease by 70 mV.