Neuronal signalling 4 (2nd lecture) Flashcards
Which ligand gated ion channel causes an EPSP?
Na+
Which ligand gated ion channels cause an IPSP?
K+ and Cl-
How is does the membrane potential reach the threshold?
Via many EPSPs
What is the threshold?
The membrane potential which causes the VG channels to open
What is the resting potential of the neuron dependent on?
The balance of the ions on either side of the membrane
At rest, what makes up the bulk of the -ve charge in a neuron?
Anions (proteins)
Resting concs of Na+ and K+?
Na–> Low in cell, high outside of cell
K+–> High inside cell, low outside of cell
What is resting potential?
membrane potential of a neurone that is not being stimulated (determined by the Goldman Equation)
What is equilibrium potential?
the potential of the membrane, for a single ion that that stops further movement of that ion across the membrane (Nernst Equation)
What is reversal potential?
potential at which no further charge movement across the membrane occurs
What is the same for the movement of one ion?
Reversal potential and equilibrium potential
What is summation?
Integration of many diff EPSPs and IPSPs
Two mechanisms of summaiton?
Spatial and temporal
Spatial summation?
multiple stimulation at one synapse in a short period of time-> additive
Temporal summation?
simultaneous stimulation from two or more nearby synapses; each synapse is excitatory or inhibitory
Does temporal summation have to have the same type of input
No–> can be one EPSP then an IPSP which cancels out the EPSP
First event following threshold being reached?
VG Na+ channels open
When does Na+ stop moving into the cell through VG channels?
Opposing force of the charge inside the cell prevents further movement
reversal potential
What happens when no more Na+ can enter the cell?
K+ channels open which allow K+ to leave the cell
What is the result of K+ moving out of the cell?
Repolariation
Hyperpolarisation?
Dip below the resting potential following an AP
How many phases does an AP have?
4
Phases of an AP?
Depolarization–> VG Na+ open
Repolarization–> VG K+ open
Hyperpolarization–> refractory period
Fourth phase–> return to resting pot
State of Na+ channels during hyperpolarisation?
Inactivated–> not really closed
cant respond to a change in membrane potential
Role of refractory period?
Governs how the AP propagates along the axon
Two parts of refractory period?
Absolute and relative
Which ion channels produce an AP?
Na+ and K+
How is an AP carried from one region of an axon to the next?
Passive spread of current
What is used to restore the Na+ gradient?
Na,K antiporter (pump)
What does the Na,K antiporter do?
exchanges two K ions from outside the cell with 3 Na ions from inside the cell and uses ATP.
