Action potentials Flashcards
How does a neuron transport electrical signals?
Action potentials
Brief change in voltage across membrane
What is value of resting membrane potential?
-70
Inside more negative
At resting where are concentrations ions?
K+ higher conc inside
Na and CL higher conc outside
Provides conc gradient
At rest what is movement of ions?
K+ out
Na and CL move in
What maintains conc gradient? What ions
Na+/K+ ATPase channels
Active transport (antiport pump)
3 Na+ out for 2 K+ in
Outline steps generating action potential?
1) AP start at the axon hillock due to depolarisation
2) During depolarisation voltage-gated sodium ion channels open
More sodium voltage gated ions open
3) Sodium rushes into cell +30mV
4) Charge inside beings increase
5) Threshold reached- action potential is produced
6) Sodium ion channel closes
7) Positive charge inside cell causes potassium channels to open, K+ move out of cell
8) Membrane potential fall to resting potential
9) Repolarisation overshoots- hyperpolarisation
10) Action potentials are followed by refractory period
During depolarisation what is value inside cell?
+30mV
What causes initial depolarisation?
Sodium ions
What is the threshold response called?
All or nothing
What repolarises cell?
K+ ions out
What are 2 types of refractory periods? Explain?
Absolute refractory- AP can’t be generated
Relative refractory- AP fired if stimulus strong enough
Draw AP graph with 5 labels?
1) Na+ voltage gated channels open
2) More Na+ channels open
3) Na+ channels close
K+ channels open
K+ out
4) Hyperpolarisation membrane
5) Refractory period- Na+ out K+ in
At what voltage does AP fire?
-55mV
What is maximum votage?
30 or 35mV
What is movement ions in refractory period?
Na+ out
K+ in
