topic 8 - nervous transmission Flashcards
what is the value of the resting potential?
-70mv
what i the most prevelent ion on the inside of the cell membrane?
K+
how does the sodium-potassium pump maintain a higher concentration of potassium ions inside the cell and sodium outside?
2 K in for every 3 Na out
How do electrostatic forces maintain equilibrium in the cell?
as K+ moves out of the cell via ion channels, the inside of the cell becomes more negative attracting the K+ back in. to the cell.
how is threshold potential reached?
when neurotransmitter binds, na+ move in to the cell causin it to become more positive.
around -55mv
how does depolarisation occur and an action potential fired?
stimulation causes voltage gated Na+ ion channels to open creating an influx of Na+ ions into the cell
charge increases to +40 mv and an actionpotential is fired
what happens after an action potential ?
- when voltage has peaked
- voltage gated Na+ ion channels close
- voltage gated K+ ion channels open
- influx k+ out of cell
- repolarisation of cell
what does the myelin sheath do?
- insulate and protect neurons
- increase speed of nerve impulse
describe how the myelin sheath speeds up nerve impulses
- signal jumps from one node of ranvier to the next
- saltatory conduction
define the refractory period
- where an action potential cannot be stimulated again instantly
- ensures that the wave of depolarisation travels in one direction.
what is hyperpolarisation?
so many K+ are transported out of the cell that the potential difference becomes further away from 0 than it was at resting potential
describe what happens when habituation occurs (5)
- calcium channels become less responsive
- reduced amount of calcium ions crossing membrane
- less neurotransmitter released
- less depolarisation
- no action potential triggered
define habituation
when an organism becomes insensitive to a repeated stimulation over time
