2. Neuronal transport Flashcards
name the specialised rough ER in the cell body
Nissl Substance
how long is the sciatic nerve
over a metre
name neutrons specialised intermediate filament
neurofilament
what is the function of microtubules
facilitates movement within the cell
how are microtubules affected in Alzheimers
microtubule associated protein Tau is destabilised- disrupting cell transport
what are neurofilaments involved in
involved in motility, structural support and axonal transport
describe anterograde transport
materials are transported from the soma to the axon terminals
what is the soma
the cell body
what is anterograde transport also known as
orthograde transport
describe retrograde transport
transport of materials from the axon terminals to the soma
what type of materials are transported in anterograde transport
small vesicles, enzymes
what type of materials are transported in retrograde transport
larger vesicles, nerve growth factor
which is a faster method of neuronal transport
anterograde (fast= 200-400mm/day)
retrograde= 200 mm/day
what two forces move ions across membranes
chemical force
electrical force
describe chemical force
differences in concentration cause diffusion of molecules (high conc -> low conc)
describe electrical force
movement on ions based on charge of the cell vs the extracellular environment
what is the term to describe the combination of electrical and chemical force
the electrochemical driving force
what are the three types of gated channels
1) ligand gated channels
2) mechanically gated channels → activated by physical force eg pressure
3) voltage-gated channels
what are the two broad categories of ion channels
gated channels and open channels
describe ion concentration under resting conditions
low Na+
high K+
describe potassium movement under resting conditions
constant flow of K+ ions down their concentration gradient out of the neuronal via open K+ channels
what is the purpose of the sodium potassium pump
prevents an equilibrium forming
pumps 3na+ OUT
2k+ IN
results in a more positive charge outside the neuronal
what is the resting membrane potential of most cells
-70 mV
describe what happens to electrochemical gradients when sodium channels open
- chemical gradient drives diffusion into cell
- electrical force pulls ions into cell (attraction)
- NA+ enters cell
- neuron becomes more positive → forces decrease
- forces balance = no nett flow
describe what happens to electrochemical gradients when potassium channels open
- chemical gradient= diffusion out of cell
- electrical force= attraction into cell
- chemical force greater than electrical force
- potassium leaves neuron
- cell becomes more negative
- chemical force driving out and electrical force driving in balance= no nett flow
define equilibrium potential
the membrane potential required to counteract chemical forces acting on one ion across a membrane
what equation calculates equilibrium potential
Nernst equation
