What Is Pain?

Explore nociception at its three main levels of organization-the molecular level where specific pain proteins are stimulated, the cellular level where nociceptors generate electrical signals, and the circuit level where nociceptors make connections with neurons in the spinal cord. Learn about the different types of nociceptors and the difference between reflexive and relay circuits.

Explore the distributed network of the many brain regions activated during the perception of pain. But what's happening with the 85% of people with chronic back pain who have no physical cause for the pain? Could the brain itself be the problem? And given that the brain does not contain nociceptors, what causes the severe pain of headaches?

If you burn your finger, nociceptors begin the process that alerts your brain to tissue damage. But how your brain responds to those signals depends on your mental state. Learn how your attention, emotions, mindset, fatigue, expectations, beliefs, social context, and even hunger and thirst can all significantly influence your perception of pain.

Explore the endogenous opioid system, a complex network that plays a crucial role in modulating pain, pleasure, and overall well-being. Learn about the different types of neurotransmitters and neurotransmitter receptors spread out across our nervous system. And discover why dysregulation of this system has been implicated in many medical conditions.

While every living organism can react to aversive stimuli, to what extent do animals experience pain as humans have defined it? Learn about experiments scientists have undertaken with a wide variety of animals to try to answer that complex question. From the flatworm to the zebrafish to the octopus, we do see animals with certain aspects of our own pain processing systems.

The neurological system that processes signals and interprets pain keeps us alive. But what happens when the system itself is damaged? Explore the many dimensions of neuropathic pain and learn how it can result from diabetes, chemotherapy, direct nerve injuries, or multiple sclerosis. Learn about some of the most common forms of chronic neuropathic pain.

Learn about inflammatory pain-with arthritis being the most well-known-and how it differs from neuropathic pain. Explore how the immune and nervous systems constantly influence each other and play a role in chronic conditions like autoimmune diseases and neurological diseases. You'll also learn about microglia, immune cells of the brain and spinal cord, and the role they play in pain perception.

At any given moment, about 25% of the adult population is experiencing visceral pain. And yet, the diagnosis and treatment of chronic visceral pain is often extremely difficult-at least for now. Learn about the differences between the body's processing of internal versus external pain and explore the enteric nervous system.

While all humans have 99.9% of the same genes, what makes us unique is the expression of those genes. Discover the phenomenon of epigenetics-an important regulator of gene expression-and the role it plays in the variation of pain perception and tolerance between individuals. Also, explore what happens when genes that encode important pain proteins mutate and how that can affect pain tolerance.