Sensory Pathways: Nociception Flashcards
Compare the receptive fields of nociception to those of touch.
Receptive fields for nociception are much LARGER because the nociceptive pathway is phylogenetically older than touch and you don’t need to be able to localise pain as well as touch.
Describe the method of coding intensity in nociception.
Same as touch – increase in frequency of impulses
What is the role of the primary somatosensory cortex in processing the nociceptive stimulus?
It registers the LOCATION and INTENSITY of the stimulus
As the spinothalamic tract projects towards the primary somatosensory cortex, it gives off collateral branches. Whichstructures do these branches go to?
Brainstem (reticular formation)
Thalamus (intralaminar nuclei)
Hypothalamus
Limbic structures
What is the point of the collateral connections from spinothalamic tract to reticular formation and intralaminar nuclei?
The connections to the reticular formation and intralaminar nuclei allow the spinothalamic tract to increase your level of arousal to make sure that you are aware of potentially harmful situations.
Which CNS structures are involved in signalling the unpleasantness of a stimulus?
Limbic structures and hypothalamus
What are the two pathways that can reduce the amount of pain that you feel?
Central and Peripheral Inhibition Pathways
What type of molecule is Enkephalin?
Opioid
Morphine mimics the action of this central inhibition system.
Other than a first order nociceptive neurone, what else has inputinto the second order nociceptive neurone?
Non-nociceptive neurones
Axons of non-nociceptive touch neurones will go into the dorsal horns but will also have collaterals that are capable of activating an inhibitory interneurone, which can reduce the activity of the projecting neuroneand hence reduce the activity going up the spinothalamic tract.
Describe the arrangement and function of the peripheral inhibition pathway.
Stimulation of touch receptors in the same area as the pain sensation will lead to increased activity of the non-nociceptive touch neurones meaning that there is increased activation of the inhibitory interneurone and hence reducing the activity going up the spinothalamic tract.
Sensory component of pain pathway
Spinal chord to thalamus to cortex
2 components of pain pathway
Sensory and emotional
Sensory = spinothalamic
Emotional= spinoreticular
Hyperalgesia
Increased pain from a stimulus that normally provokes pain
Allodynia
Pain from stimulus that doesn’t normally provoke pain
