PSL300H1 Chapter 4: Chapter 4 Impulse Transmission
Document Summary
Length constant is the distance traveled before a potential difference drops to. The greater the , the faster impulse conduction can occur. Can be increased by reducing leakage of depolarizing current across membrane. Increasing membrane resistance, decreasing internal resistance of axoplasm (do this by increasing axon diameter). Increasing axon diameter has limitations (space, nutritional support). Increasing membrane resistance more practical for increasing . Increase resistance by adding myelin sheath (glial cells) Space between successive glial cells (scwann in pns, oligodendrocytes in cns). Necessary opening for the ionic fluxes generating new spike to boost decrementing voltage of prior impulse. Nodes contain high density of voltage-gated na+ channels. K+ are located in internodes where they cannot function. Action potentials can only be generated at nodes of ranvier. Conduction velocity determined by number of nodes along axon. Impulse propagates in longer leaps in fast conducting axons. Saltatory conduction: leaping mode of transmission made possible by myelination.
