Potentials Flashcards
Explain how the resting potential of –70 mV is maintained in the sensory neurone
when no pressure is applied.
- Membrane more permeable to potassium ions
and less permeable to sodium ions; - Sodium ions actively transported/pumped out
and potassium ions in;
Explain how applying pressure to the Pacinian corpuscle produces the changes in
membrane potential recorded by microelectrode P.
- (Pressure causes) membrane/lamellae to
become deformed/stretched; - Sodium ion channels in membrane open and
sodium ions move in; - Greater pressure more channels open/sodium
ions enter;
The membrane potential at Q was the same whether medium or heavy pressure
was applied to the finger tip. Explain why
- Threshold has been reached;
- (Threshold or above) causes a maximal response
/ all or nothing principle;
Multiple sclerosis is a disease in which parts of the myelin sheaths surrounding
neurones are destroyed. Explain how this results in slower responses to stimuli.
- Less/no saltatory conduction / action
potential/impulse unable to ‘jump’ from node to
node; - More depolarisation over length/area of
membranes;
Define nerve impulse
self-propagating wave of electrical energy that travels down axon membrane
Name the resting potential in humans
-65mV
Describe how the resting potential is established
S/K pump actively transports Na+ out at a greater rate of P+ in. 3 Na+ for 2K+
Electrochemical gradient due to move Na+ outside than inside axon. Vice versa with K+
Describe how the action potential is established
Stimulus detection causes a temporary reversal of charges above the threshold
Na+ voltage-gated channel open so Na+ enter the axon down their con. gradient
This causes a positive feedback mechanism along the axon
The axon becomes depolarise and the membrane potential reverses
Na+ channels close and K+ channels open
K+ leaves via electrochemical gradient
Hyperpolarization occurs
Na/K pump restores resting potential hence repolarisation
Name the action potential in humans
40 mV
Describe what an action potential is
A travelling wave of depolarisation
How does the impulse travel down a myelinated neurone?
salvatory conduction ( faster)