PSYC23H3 Lecture 10: PSYC23 - Lecture 10 - Mar22.docx
Document Summary
2 distinct branches of the vagus nerve --> different evolutionary stress responses in mammals: older system --> primitive --> fight/flight behaviour (immobilization, new system --> more evolved --> linked to inhibition of behaviours, communication and self-soothing. Opposes the sam stress response --> sympathetic-adrenal system. Vagal tone physiological indicator of stress. Structures: dorsal motor nucleus (dmnx) --> older system --> vegetative vagus. Activated when the more evolved branch fails. Ventrolateral motor nucleus (na) --> newer system (more evolved) --> smart vagus: mylinated vs. unmylinated --> some vagal fibers are mylinated and some aren"t --> Mylinated = more efficient = activated by the newer system (likes to operate. Organization with the smarter one: hierarchical --> over the course of evolution we"ve been adding newer and newer systems --> cumulative effect, integrated into the older system. Seeing a new species develop, you can see shapes of the older structures that are from ancient species; from much earlier primitive species: dissolution.