sensory and motor nerves Flashcards
what is current flow impeded by ?
resistance
what can voltage decay be defined by
space constant - how far voltage travels
- determine by axonal resistance
time constant - how fast voltage travels
- determined by resistance and capacitance
what increases space constant?
myelination
axon diameter
what is the voltage across a cell membrane determined by ?
balance of electrical and chemical forces
what does hyper-polarisation do ?
make AP less likely
what does hypo-polarisation do ?
make AP less likely
why is the Na+ pump crucial ?
establishes membrane potential necessary for action potential
otherwise Na+ and K would leak
how’s does Na+ and K channels differ
Na+ channels open quickly
K channels open slower
why does the refractory period prevent the positive feedback cycle continuing
ensures AP only travels in one direction
what facilitates AP speed ?
higher temperatures
what is role of myelin sheath?
increase speed of current
increases space constant
what conditions are caused by demyelination?
multiple sclerosis
guillian-barre syndrome
