NURS113 Lecture 3: PNS and Pain
5 Dec 2017
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System lesson 1: brain figure out type of stimulus by: type of receptors, photoreceptors//mechanoreceptors//thermoreceptors// Osmo-receptors// chemoreceptors: nociceptors pain receptors (can be mechanical, thermal, chemical or polymodal , simulates modality by specific pathways lateral spinothalamic tract pain, temp. Posterior column tract fine touch, discriminative sensation, vibration: location of stimulus. **receptive field size = somatosensory neuron + circumscribed region of the skin surface. **body somato-topically: lower limb lumbar, sacral, coccygeal nerve. **homunculus map coronal, frontal cut posterior, anterior: stimulus strength by frequency of action potential (if frequency is high, sensation is strong) Lesson 2: pain: subjective; primary a protective mechanism; unpleasant experience. /// sensory fibres accumulate and begin to signal pain once threshold achieved. ///intensity overtime and area determines whether pain is recognized: gate control theory: pain transmitted by a large a delta and small c fibres. Stimulation of large fibres can close the gate of small fibres.
