Question

question 4 of 10
when you touch something hot, a neuron in your finger senses the temperature. which best describes the first reaction the neuron has?
a. neurotransmitters cross a synapse.
b. sodium atoms travel through the veins.
c. ions flow out of the neuron.
d. an action potential forms.

Explanation:

When a neuron senses a stimulus (like heat in this case), the first reaction is the formation of an action potential. An action potential is an electrical signal that allows the neuron to communicate the detected stimulus.

• Option A: Neurotransmitters crossing a synapse occurs later in the communication process between neurons, not as the first reaction of the sensing neuron.
• Option B: Sodium atoms do not travel through veins (which are part of the circulatory system for blood, not for neural signaling). In neurons, sodium ions (\(Na^{+}\)) are involved in action potential generation but not in the way described here.
• Option C: During an action potential, sodium ions (\(Na^{+}\)) flow into the neuron (not ions flowing out as the first reaction). The first key event is the depolarization (associated with action potential formation) which involves ion movements but the overall first reaction is the action potential forming.

Answer:

D. An action potential forms.