Potentials Flashcards
1
Q
Membrane potential
A
- the difference in electrical charge inside and outside of a cell
- (-)70 mV is a neurons resting potential
- potential inside a resting neuron is less than outside
- measured with electron inside and outside of a cell
2
Q
Ionic basis of resting potential
A
ions: positively and negatively charged particles
- sodium and potassium carry a single positive charge
- in resting state more Na+ outside, more K+ inside
- pressure for Na+ ions to enter the cell bc of electrostatic pressure and movement down the concentration gradient
- sodium ions are closed in resting potential preventing Na+ ions to enter
_ potassium channels are open but K+ stay inside because of the negative membrane potential
3
Q
Postsynaptic potential
A
- neurotransmitters are released from neurons when they fire and bind to receptors and depolarise or hyperpolarise the membrane of the postsynaptic neuron
excitatory postsynaptic potential: depolarisations that increase the increase the likelihood that a neuron will fire
inhibitory postsynaptic potential: hyperpolarizations that decrees the likelihood that a neuron will fire
balance between EPSP and IPSP determine if a neuron will fire
4
Q
Action potential
A
- massive reversal of the membrane potential that lasts 1ms
- AP are generated if the EPSP and IPSP at the axon initial segment are enough to depolarise the membrane potential to the threshold of excitation (-65mV)
- if membrane is depolarised, sodium channels open, na+ ions rush in.
- potassium channels open to counter this
5
Q
Refractory periods
A
- after an AP it is impossible for another to occur in 1-2 ms (absolute refractory period)
- make the AP travel in one direction along the axon
- increase the rate of firing in reponse to intensity of stimulation
6
Q
Conduction of Action potentials
A
- in myelinated neurons the AP is conducted passively along the myelin segments
- increases the speed at which the AP is travelling
