Question

If a postsynaptic neuron has several excitatory and inhibitory synapses active at the same time, that postsynaptic neuron __________ fire an action potential. For example, if we are looking a yellow object, both our red and green cones are activated; however, we do not perceive that object as red or green because the signals from the red and green cones to “green-on” and “red-on” ganglion cells will _________. In addition to multiple synapses affecting the likelihood of an action potential firing, if a neuron has a single synapse and a visual stimulus is too weak to reach threshold (e.g. the light is too dim for us to see the color yellow), we ________ generate an action potential.

Group of answer choices

Is likely to; have additive effects; most likely will not

Is unlikely to; cancel each other out; most likely will not

Is likely to; cancel each other out; most likely will

Is unlikely to; have additive effects; most likely will

Answer 1

The answer is option (a) is likely to; have additive effects; most likely will not.

If a post synaptic neuron has several excitatory and inhibitory synapses, active at the same time that post synaptic neuron is likely to fire an action potential.

This is due to a phenomenon known as summation. Summation can be temporal or spatial. In spatial summation, there are multiple simultaneous input from different sources to the post synaptic neuron while in temporal summation there are repeated inputs from a single source to the post synaptic neuron

Even if each input is below the threshold level, they add together to generate the threshold necessary for an action potential.

But if the neuron has a single synapse and if the impulse from this synapse is too weak to reach the threshold, the neuron will not generate an action potential.