Question

A certain neuron in a mouse brain is firing about 300 times per second, whereas almost all of its neighboring neurons are firing at much lower rates of only a few times per second. This

implies that ...
A. this neuron expresses more depolarizing (Na⁺ and Ca²⁺) than hyperpolarizing (K⁺) channels compared to most of its neighbors.
B. the mouse is experiencing an epileptic seizure.
C. the refractory period of its voltage-gated Na+ channels is at least 300 ms.
D. it releases excitatory neurotransmitters at its axon terminals.
E. it is probably of a different type compared to most of its neighbors.

Answer 1

A neuron firing 300 times per second compared to its neighbors suggests it may have more depolarizing channels or release excitatory neurotransmitters, not necessarily indicative of a pathology or a fundamentally different neuron type.

option (A)

Step-by-step explanation:

The observation that a certain neuron in a mouse brain is firing about 300 times per second, significantly more than its neighbors, could imply several things. However, since action potentials are all-or-nothing events and because the refractory period follows depolarization during which sodium channels are inactivated, option C is incorrect (the refractory period cannot be 300 ms if the cell is firing 300 times per second, as this would imply only one action potential could be fired per second).Options B and E are speculative without additional context.

They suggest a pathological condition or a fundamental difference in neuron type, which cannot be assumed solely based on firing rate. The most likely answer is A or D. If the neuron expresses more depolarizing channels (Na+ and Ca2+), it would allow for more frequent depolarization events relative to hyperpolarizing influences. Alternatively, if the neuron releases excitatory neurotransmitters at its axon terminals, it could continually excite itself or neighboring neurons that synapse onto it, keeping its firing rate high. The firing rate alone is not enough to deduce the specific internal mechanisms or external functions, but it does suggest that the neuron might have a different level of excitatory activity compared to its neighbors.