nerve impulses action potentials Flashcards
what is an action potential
+40mV
what type of feedback is used for action potentials
positive feedback- increasing a change taking the system further away from the optimum
what does it mean if a neurone is at rest
when a neurone transmitting an action potential- it is at rest
only pumping ions across its plasma membrane, by a sodium potassium pump
3 sodium in, 2 potassium out
what is the sodium potassium pump
3 sodium in, 2 potassium out.
describe the neurone at rest
- Sodium gated channels are closed
- some Potassium gated channel is open
- sodium-potassium pump on (3 sodium out, 2 potassium in)
at rest, what ion is the neurone more permeable to
at rest, the plasma membrane is more permeable to potassium ions therefore they diffuse out.
what is present in the cytoplasm of a neurone
large anions (negatively charged ion)
what is the resting potential
-60mV
before an action potential is the concentration of sodium ions higher inside or outside
outside plasma membrane there are more sodium ions than the inside.
potassium ion concentration is higher inside than outside
what causes depolarisation
influx of sodium ions will quickly diffuse down their concentration gradient into the cell from the tissue fluid
causing a depolarisation
what is a generator potential
happens in generator region of a neurone
when only a few sodium gated channels are opened to produce a small depolarisation.
it may go no further, or it may be used to combine with other generator potentials to produce a large depolarisation
what is a threshold
when depolarisation reaches a specific magnitiude and goes on to produce an action potential
what is the magnitude of an action potential
+40 mv
what is a voltage gated channel
a protein channel in a plasma membrane which are opened by a a change in charge/ potential difference across the plasma membrane
why is neuronal communication positive feedback
because a small depolarisation of the membrane causing a change which increases depolarisation further
what does it mean if the action potential is self perpetuating
once an action potential is acheived on one point of the neurone, it will continue along till the end of the neurone
what is the all or nothing response of an action potential
all action potentials are the same magnititude, +40mV.
therefore all neurones reach +40mV and produce an action potential or they dont.
if a stimulus is large, what happens to the action potential
action potential is MORE FREQUENT, NOT LARGER
What are the stages of an action potential
1- membrane resting potential- inside of cell -60mv. higher conc of sodium outside membrane, higher concentration of potassium inside membrane
2- sodium voltage gated ion channels open and sodium diffuse into the cell
3-membrane depolarisation- membrane becomes less negative reaching threshold -50mV.
4- positive feedback caused surrounding sodium channels to open and influx of sodium ions causing cell to be positively charged inside compared with the outside.
5- potential difference across the plasma membrane reached +40mV. inside of cell is positive, outside is negative
fully describe resting potential
- 60mV
inside membrane- high potassium
outside membrane- high sodium
Sodium-potassium pump working- yes
voltage gated sodium channel- closed
voltage gated potassium channels- closed, but leaking
fully describe depolarisation
inside membrane- high potassium and high sodium
outside membrane- decreasing sodium and low k
-60mV to + 30 mV
sodium potassium pump- yes
voltage gated sodium channel- open
voltage gated potassium channel- closed but leaking
