Have you watched Ridley Scott’s Hanibal? Remember the scene in which the eponymous Hannibal Lecter cuts out part of the brain of an FBI agent who is fully awake, though drugged, and seated at a dinner table?
Um, yes. So.
Does the brain itself have pain receptors? Nope. The brain does not feel any pain.
No pain receptors in there at all.
But the meninges (coverings around the brain), periosteum (coverings on the bones), and the scalp all have them.
So, surgery on the freaking open brain can be done technically, and it won’t feel that pain.
With that said, the brain is “just” the tool we use to detect pain inside the body.
Let’s say that you step on a random sharp object on the beach. A shell, for instance.
What happens next? You might scream and shout, yes.
Behind that painful ouch is the following:
Special pain receptors in your skin activate whenever there has been an injury, or even a potential injury, such as breaking the skin or causing a large indentation. Now, an impulse is heading through the nerve into the spinal cord, and eventually all the way to your brain.
This happens within fractions of a damn second.
Your spinal cord is a complex array of nerves, transmitting all kinds of signals to and from the brain at any given time.
The spinal cord is also in charge of your reflexes. The brain does not have to tell your foot to move away from the shell, because the spinal cord has already sent that message. The pain signal continues to the brain. This is because pain involves more than a simple stimulus and response.
Your brain needs to make sense of what has happened. Pain gets cataloged in your brain’s library, and emotions become associated with stepping on that shell. When the pain signal reaches the brain it goes to the thalamus, which directs it to a few different areas for interpretations. Some areas in the cortex figure out where the pain came from and compare it to other kinds of pain with which is it familiar. Was it sharp? Did it hurt more than stepping on a tack? Have you ever stepped on a shell before, and if so was it more or less painful?
Signals are also sent from the thalamus to the limbic system, which is the emotional center of the brain. Feelings are associated with every sensation you encounter, and each feeling generates a response. For example, your heart rate may increase, and you may break out into a sweat.
The pain experience for all of us begins when unpleasant stimuli activate sensory nerve fibers called nociceptors.
The brain has no nociceptors – the nerves that detect damage or threat of damage to our body and signal this to the spinal cord and brain. This has led to the belief that the brain feels no pain. A belief that has entered popular culture. Nice feature, tho.
These nociceptors, specialized fibers — which are located in skin, muscles, joints, and some organs — transmit pain signals from the periphery to the brain, where the message of pain is ultimately perceived.
The brain itself could be completely pain-free, but as we’ve all experienced — with headaches, however, there’s a completely different pain fairy tale.
Though your brain does not have nociceptors, there are some of them in layers of tissue known as the dura and pia that serve as a protective shield between the brain and the skull.
In some situations, chemicals released from blood vessels near the dura and pia can activate nociceptors, resulting in headaches, such as migraines.
Increased blood flow can also trigger a migraine, which is why migraines are considered vascular headaches. Migraine headaches are often throbbing and are accompanied by hypersensitivity to light, sound, and touch.
But if the brain feels no pain, what causes headaches?
Many of the other structures in our head do contain nociceptors, including blood vessels, muscles, and nerves in the neck, face, and scalp. Headaches are caused by problems with these structures.
Different types of nociceptors are activated by pressure, damage, extremes of temperature, and some chemicals, such as capsaicin (the active ingredient in chili peppers).
“Brain freeze” or “ice-cream headaches” seem to be caused by sudden changes in blood flow in the veins that lie between the back of the throat and the brain. Dehydration causes headaches by irritating the blood vessels in the head and is one reason for the throbbing head that many experiences after a night of drinking. And any dentist can tell you that a headache could indicate you over-exert your jaw, perhaps by grinding your teeth when you sleep.
In a fundamental sense, Hannibal Lecter was wrong about the brain feels no pain. Although the brain has no nociceptors, the brain “feels” all our pain. This is because our brain is the organ through which we interpret, evaluate, and experience all the sensory signals from our body.
Scientists distinguish between nociception – the nervous signal of damage to our body – and pain, the unpleasant emotional and cognitive experience that normally results when our nociceptors are activated.
This means that pain is more than just a sensory experience, it is influenced by our thoughts, feelings, and social relationships.
For example, how we experience pain is affected by our thoughts, such as what we believe the pain might mean, and what we remember of previous painful experiences.
Pain is also an emotional experience:
people with depression report that they experience more pain in daily life. And inducing a low mood in otherwise normal people increases pain ratings and lowers tolerance to pain.
It is also a social experience.
In one experiment, students who were asked to hold their hand in painfully cold water for as long as possible tolerated the pain for longer if they thought the experimenter was one of their professors than if they thought the experimenter was a fellow student. This shows that who asks us about our pain is important.
The social influences on pain also show the benefits of having support from those who care about you.
In another study that used the same ice bucket method, people had a greater tolerance for the painful cold when another person silently observed the experiment, compared with being alone with the experimenter. And if the “observer” was a friend of the same sex, the participants had higher tolerance even if the friend was not actually inside the room, but was merely nearby.
Given the many influences on how we experience pain, it is no wonder that finding relief from pain can be complex and frustrating. The good news is, each of these influences also represents a way to manage pain. Helping people change their thoughts and feelings about their pain is an important part of pain management, as is maintaining social relationships.