BIOM30001 Lecture 25: 25 Neurochemistry Pain and Pleasure I B
Document Summary
Generates ap in axon, and bypasses receptive field. Increase strength of stimulus and progressively recruits more fibres. A fibres are larger and myelinated: have lower threshold/more easily stimulated. Activation of slower conducting a (nociceptors): pricking pain. Stimulating c fibres gives you a slow type of pain (e. g. burning pain) First pain: pain associated with a fibres - sharp, cutting. Second pain: burning and aching which persists after stimulation. Responsible for the sensory discriminative aspects of pain perception. We don"t perceive pain unless afferent signal is relayed to the cortex. Note: 1st/2nd/3rd order neurons in the pathway - 1st order neuron is the first afferent neuron. If the pathway is not intact (anaesthetic, spinal cord injury) we don"t feel pain. May be possible to still get a spinal cord reflex with no pain (withdrawal reflex) Both have very high threshold. e. g pressing a pen into the skin will activate mechanoreceptors but not nociceptors.
