Question

A postsynaptic neuron has three presynaptic inputs - from neurons X, Y, and Z. Stimulation of neuron X causes the postsynaptic neuron to depolarize by 0.5 mV. When X and Y are stimulated simultaneously, the postsynaptic neuron depolarizes by 1 mV. When X and Z are stimulated simultaneously, however, there is no change in the membrane potential of the postsynaptic neuron. What is most likely true about presynaptic neurons Y and Z?

Answer 1

Answer:

Y is probably excitatory and Z is probably inhibitory

Explanation:

• Two neurons communicate with each other generally by releasing neurotransmitters.
• The neuron which releases the neurotransmitter is termed as presynaptic neuron and the neuron to which the neurotransmitter binds to exert its effects is called as postsynaptic neuron.
• Based on the nature of the neurotransmitter released, the presynaptic neurons can either be inhibitory or excitatory in nature.
• The change in the membrane potential of the postsynaptic neurons depends on the total sum of inputs coming from different pre synaptic neurons at a given time.
• From the given situation, the stimulation by X alone is causing deploarization of 0.5 mV which shows that it is causing excitation, and since depolarization is increasing when X and Y are stimulaneously stimulated Y is also excitatory in nature. However the depolarisation is not occurring when X and Z are stimualted together and hence, Z is probably inhibitory in nature.