Lecture 2 Action potential Flashcards
Where is potassium K+ concentration higher
Inside the cell
Intracellular
Where is the Na+ ions higher
Outside of cell
Extracellular
Where is cl higher
Extracellular outside
Where is ca higher
Outside
Extracellular
What creates the membrane potential
Ion concentration between Extracellular membrane fluid and Intracellular Membrane fluid
And selectively permeable cell membrane
What is the effect of K ions leaving the cell
Inside of cell more negative outside more positive
Resting potentials
Charge across the membrane at rest
Ie ion channels not open
Hyperpolarisation
Membrane potential MORE negative
Dip in graph
Net increase in negative charge inside cell
Depolarisation
Membrane potential less negative
Peak in graph
Net decrease in negative charge inside cell
Repolarisation
Membrane potential returns to rest
What does cytoplasmic Na bind to
Sodium potassium pump
What enzyme used in membrane potential
Na/k ATPase
What stimulates the phosphorylation of the pump by ATP
Na binding
Effect of phosphorylation
Protein change shape = na outside
Extracellular K binding
Protein triggering release of phosphate
Loss of phosphate
Original conformation
When is cycle repeated
K + released and Na+ sites are free
Action potential
Signalling event that involves rapid change in membrane potential if nerves
Resting potentials
No movement of ion membrane potential at rest
Threshold potential
Minimum voltage required to start an action potential -55mV
Depolarisation
Membrane potential less negative
Repolarisation
Bringing back membrane potential to resting membrane potential
Hyperpolarisation
Influx of potassium ions, membrane potential more negative
Absolute refarctory period
Impossible for an action potential to take place
No stimulus can trigger
Relative Refractory period
Only a larger than normal stimulus can initiate a new action potential
Inhibitory stimulus
Hyperpolarisation
Excitatory stimulus
Depolarisation
Continuous propagation
Signal moves along the axon, energy passed along
Amplitude of action potential does not change
Rate dependent on diameter of neurons
Saltatory conduction
Very fast
Local current moves between nodes of ranvier
Conduction rate faster than unmyelinated neuron of same diameter
Action potential propagation
Continuous / saltatory
