Biological Systems MCAT Practice Exam

Which neurotransmitter is primarily involved in signaling within the somatic nervous system?

1. Dopamine

2. Serotonin

3. Acetylcholine

4. Norepinephrine

The correct answer is: Acetylcholine

The somatic nervous system is responsible for controlling voluntary movements by transmitting signals to skeletal muscles. Acetylcholine is the primary neurotransmitter involved in this signaling process. When a nerve impulse reaches the neuromuscular junction, acetylcholine is released from the motor neuron and binds to receptors on the muscle fibers. This binding induces muscle contraction by triggering changes in the muscle cell membrane's permeability, allowing for muscle activation. In contrast, the other neurotransmitters listed, such as dopamine, serotonin, and norepinephrine, play more significant roles in the central nervous system or the autonomic nervous system, where they influence mood, arousal, and involuntary functions, respectively. Thus, acetylcholine's specific role in synaptic transmission at the neuromuscular junction distinguishes it as the key neurotransmitter for the somatic nervous system.