Question

When a typical neuron’s membrane potential reaches +30mv, all of the following will be true except:

a) the voltage gated potassium channels will open

b) the neuron will be in absolute refractory period

c) the neuron will have generated an action potential equivalent to 100 mb

d) the voltage gated chloride channels will open

e) the voltage-gated sodium channels will close

2)Which of the following open or closes in response to neurotransmitters binding to their receptors?

a) sodium voltage-gated channels

b) sodium/potassium pump

c) ligand (chemical) gated channels

d)calcium voltage gated channels

e) leak (passive) channels

Answer 1

1) Answer - Option C

The next phase after reaching the depolarisation phase of +30mV is the repolarization phase, This phase events are characterized by returning of the action potential to the resting membrane potential.

So the events are opening of the voltage-gated K channel with the closing of the voltage-gated Na channel as the increase the membrane potential of positivity should be reduced by the removal of the K ions from the interior and reducing the influx of the Na inside the neuron.

It is the absolute refractory period as the second action potential will not occur during this period without the completion of the first action potential thus preventing the overlapping of the action potential.

Ater this excitatory postsynaptic potential the inhibitory postsynaptic potential must occur which is characterized y the opening of the voltage-gated chloride channels.

The action potential generated by the neurons will be at a maximimum of +30mV not 100mV so the answer is option C

2) Answer is ligand-gated channels

neurotransmitters released from the presynaptic neuron bind to the postsynaptic receptors on the postsynaptic membrane.

Postsynaptic receptors are special signal recognition proteins which on binding with the neurotransmitters increases the permeability of ion channels either directly or indirectly. The direct activation is by binding of the neurotransmitter is the part of ion channel and thus the neurotransmitter binding causes a conformational change that leads to the opening of the ion channels.

indirectly by binding with the metabotropic receptors such as the G protein-coupled receptor which acts as the secondary messenger for the opening of the ionotropic receptor. The ionotropic receptor is the ligand-gated channels.

sodium-potassium pump get activated for the maintenance of the resting membrane potential not with neurotransmitter binding.

The voltage-gated Ca channel open with the binding of the neurotransmitter ACh to it.

Also the voltage-gated Na channel and leak channels are opened with reposed to the neurotransmitter release. So all these ion channels are commonly known as the ionotropic channels that is the ligand-gated channel. So the answer is a ligand-gated channel.