HMB200H1 Lecture Notes - Lecture 5: Strychnine Poisoning, Vestibular Nuclei, Reticular Formation
Document Summary
Speed and timing in cns. Lecture 5: fast reflexes nervous systems evolve because they are faster than hormonal systems. Chemicals flow around body carry messages to receptors. Nervous system has a big advantage: speed. Hormones travel at the speed of blood. Simplest reflexes: fast escape reflexes voltage- gated na+ channels action potentials axons: fast (myelinated a) and slow (c) Axons: wide range of speeds. Fastest conducting axons: ones who produce fastest escape. Myelin allows for faster conduction, less waste of energy. Myelinated axons are the fasted conducting fast conducting action potentials advantage in. Fastest systems: largest and fastest axons, fastest action output (direct connections to muscles), fewest synapses. Systems that have complete circuits from beginning (sensory inputs) to motor outputs are the fast reflexes. The ones with the biggest neurons. Compound action potential shows that myelinated axons are the fastest conducting. Erlanger and gasser applied oscilloscope onto nerves to see the conduction of action potentials.
