Final answer:
Pain fibers synapse onto their second-order neuron in the dorsal horn of the spinal cord, which is part of the spinothalamic tract for transmitting pain and temperature signals. Nociceptors are responsible for transducing pain stimuli and a bundle of axons in the peripheral nervous system is known as a nerve.
Step-by-step explanation:
Pain fibers, which include C fibers and A-delta fibers, synapse onto their second-order neuron in the dorsal horn of the spinal cord. So, the answer to the question 'Pain fibers (C and A-delta) synapse onto their ______ order neuron in the dorsal horn' is b. 2nd.
These second-order neurons form part of the spinothalamic tract, transmitting pain and temperature signals to the brain.
The initial neuron in this pathway starts in the dorsal root ganglion and then synapses with the second-order neuron in the dorsal horn.
This second neuron's axons cross to the opposite side of the spinal cord and then ascend to the thalamus, where they synapse with the third-order neurons, which in turn project to the cerebral cortex.
The spinothalamic tract is essential for the sensation of pain. This tract begins with neurons in a dorsal root ganglion, which synapse with the second-order neurons in the dorsal horn.
Nociceptors are the type of receptor cells responsible for transducing pain stimuli (answer to the review question: b. nociceptor).
A bundle of axons in the peripheral nervous system is called a nerve (answer to the reference question: d. nerve).