Piper accidentally cuts her finger while chopping vegetables. why does she feel pain?

She feels pain due to the presence of nociceptor in her body.

Nociceptor is a specialized sensory neuron capable of sensing noxious stimuli that is, the signals produced from damaged tissue or threat of damage.

They send these threat signals to the spinal cord and brain with the help of peripheral nervous system.

These signals are then processed in the thalamus of the brain.

The thalamus then forwards these signals to various parts of the brain such as somatosensory cortex (it causes physical sensation), front cortex (involve in thinking process), and limbic system (connected to emotions).

Together, they produced the sensation of pain.

It directs the attention towards the damaged body part and help in minimizing the damage or threat of damage.

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.