Final answer:
The protein that receives neurotransmitters and initiates a new action potential is called a receptor protein.
Step-by-step explanation:
The protein that receives neurotransmitters and helps initiate a new action potential is called a receptor protein. When the neurotransmitter binds to the receptor protein on the target neuron, it causes a change in the electrical state of the cell membrane, leading to the generation of a new graded potential. If this graded potential reaches threshold, an action potential is initiated.