Pain signals often have two components: an acute sensation of "first pain" which is felt almost immediately after an injury, and a sensation of "second pain" which is felt slightly later after the injury. This suggests that neurons that send the signals that we perceive as first pain ___, and neurons that send the signals that we perceive as second pain ___.

This suggests that neurons that send the signals that we perceive as first pain Myelinated Tpye A-delta___, and neurons that send the signals that we perceive as second pain Unmyelinated-Type C.___.

Explanation:

Physiologically, primary afferent neurons that innervated the the touch, pain, temperature,and pressure receptors in the effectors  to input sensory signals to the spinal cord and the brain  are categorized based on their diameter, sizes, and nature of  myelination. Based on this;

A-alpha has the largest diameter, myelinated, and sensitive to sensation from the muscle cells

A-beta are next in diameter, myelinated and sensitive to sensation  of touch.

A-delta followed in diameter, and  size. They are mylinated, and sensitive to pain and temperature.

C-fibres are least in diameter, they are unmyelinated, but sensitive to pain, touch and temperature.

Therefore, if the speed of conduction,of action  potential in a neuron depends on the diameter(thickness) and myelination of the axon(saltatory conduction) :

''then, acute sensation/ first pain should be transmitted by the A-delta fibre. While the the slower/second pain should be transmitted by the slower unmyelinated - C-fibres''.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.