7.2.1 The Mechanical Senses 2 Flashcards
The thicker and faster axons convey ____ pain. The thinner ones convey duller pain, such as postsurgical pain.
sharp
Although pain messages reach the brain more slowly than other sensations, the brain processes pain information ____. Motor responses to pain are faster than motor responses to touch stimuli.
rapidly
Pain axons release two neurotransmitters in the spinal-cord. Mild pain releases the neurotransmitter glutamate, whereas stronger pain releases both glutamate and _____.
substance P
The pain-sensitive cells in the spinal-cord relay information to several sites in the brain. One path extends to the ventral posterior nucleus of the ____ and from there to the somatosensory cortex, which responds to painful stimuli, memories of pain, and signals that warn of impending pain.
thalamus
The pain pathway crosses immediately from receptors on the one side of the body to a tract ascending the ____ side of the spinal-cord.
contralateral
Painful stimuli also activate the path that goes through the reticular formation of the medulla and then to several of the central nuclei of the thalamus, the amygdala, hippocampus, prefrontal cortex, and cingulate cortex. These areas react not to the sensation but to its ____ associations.
emotional
A hypnotic suggestion to feel no pain decreases the responses in the cingulate cortex without much effect on the somatosensory cortex. That is, someone responding to a hypnotic sensation still feels the painful sensation but reacts with ____ ____.
emotional indifference
Relieving pain. The brain puts the brakes on prolonged pain by ____ mechanisms – systems that respond to opiate drugs and similar chemicals.
opioid
Opiates bind to receptors found mostly in the spinal-cord and the ____ ____ area of the midbrain.
preaqueductal grey
Later researchers found that opiate receptors act by blocking the release of ____.
substance P
The discovery of opiate receptors was exciting because it was the first evidence that opiates act on the ____ ____ rather than on the injured tissue.
nervous system
Furthermore, it implied that the nervous system must have its own opiate-type chemicals. The transmitters that attach to the same receptors as morphine are known as endorphins – a contraction of ____ ____.
endogenous morphines
The gate theory was an attempt to explain why some people ____ pain better than others and why the same injuries hurt worse at some times than others.
withstand
According to the gate theory, spinal-cord neurons that receive messages from pain receptors also received input from touch receptors and from axons descending from the brain. These other inputs can close the “gates” for the ____ ____– and we now see that they do so at least partly by releasing endorphins.
pain messages
Nonpain stimuli modify the ____ of pain. When you have an injury, you can decrease the pain by gently rubbing the skin around it or by concentrating on something else.
intensity