Question

2. Depolarization is caused by:
   1. K+ diffusing out of the neuron
   2. K+ being pumped out of the neuron
   3. Na+ being pumped into the neuron
   4. Na+ diffusing into the neuron

3. Hyperpolarization:
   1. can be caused after neurotransmitters bind to postsynaptic neurons
   2. means the neuron’s internal environment is even more positively charged than usual
   3. can be caused by sodium ion gated channels being open
   4. each of the above is correct

4. Typically, an unmyelinated small diameter axon would have:
   1. a faster speed of action potential transmission than a myelinated small diameter axon
   2. a slower speed of action potential transmission than an unmyelinated large diameter axon
   3. the same speed of action potential transmission as an unmyelinated large diameter axon
   4. none of the above is correct

5. Several neurons each releasing a subthreshold level of neurotransmitter, all at one time, leading to an action potential in a postsynaptic neuron is an example of:
   1. hyperpolarization
   2. spatial summation
   3. temporal summation
   4. none of the above is correct

5. Depolarization causes:
   1. the interior side of the membrane to become more negative
   2. voltage-gated sodium ion channels further down the axon to open
   3. Na+/K+ pumps that were not working, to now start working
   4. each of the above is correct

Answer 1

​​​​​​1st part-

correct answer is - caused by sodium pumped into the neuron. In depolarization, sodium ions are actively transported into the neuron by sodium channel. Diffusion does not take place.

2nd part-

Hyperpolarization is caused after neurotransmitter binds to postsynaptic neuron. Option 3 is incorrect because hyperpolarization occur due to efflux of potassium or influx of chloride ion, not due to sodium. Second option is incorrect because in hyperpolarization, inside of neuron becomes more negative, not positive.

3rd part-

Option 2 is correct- will have slower speed of action potential in unmyelinated larger diameter neuron.

Action potential speed depends upon 3 things

1. Myelin sheath- it increases velocity

2. Diameter- higher the diameter, higher is velocity.

3. Temperature- higher is the temperature, higher is velocity.

4th part-

Coreect option is option 2. In spatial summation, multiply neurons release neurotransmitter at a same time. In temporal summation, one neuron release neurotransmitter multiple times.

5th part-

option 2 is correct. During depolarization, the voltage gated sodium channel are open, which lead to sodium influx . This cause inside of neuron to become more positive.