Question

An IPSP (inhibitory post-synaptic potential) occurs when a membrane becomes more permeable to ____.

ATP

neurotransmitters

sodium ions

potassium ions

Answer 1

Answers

potassium ions

Explanation: IPSP prevents the formation of the action potential in postsynaptic neurons. Binding of neurotransmitter receptors present on the postsynaptic membrane to neurotransmitter causes the opening of K+ and Cl- ion channels. The entry of Cl- inside and K+ outside will generate a more negative charge inside of the postsynaptic neurons (figure). This causes hyperpolarization. For the generation of the action potential, depolarization must take place. But the opening of the Cl- channels due to binding of the neurotransmitter to the receptors, prevents depolarization. This keeps the membrane hyperpolarized and prevents the formation of the action potential.

Explanations for wrong answers

There is no role of ATP to play in IPSP. The neurotransmission is generally governed by charged molecules whose change in the concentration changes the polarity of the membrane and initiates or prevent the action potential. ATP does not carry any charge (it is neither cation nor anion), hence it does not have any role in the neurotransmission.

Binding of the neurotransmitters to receptors mediates the opening of particular channels like K+ and Cl- (figure). Neutroasmitters plays a role in inhibitory postsynaptic potential, excitatory postsynaptic potential and action potential. In the question, they have asked to which ion or molecule membrane will be more permeable. Neurotransmitters cause membrane more permeable to ions like K+ and Cl-. Hence this can't be the answers.

The opening of sodium channels has a vital role in depolarization and hence generates an action potential. However, in IPSP depolarization does not take place. Therefore no role of sodium in IPSP.