Membrane Potential Flashcards
What is the definition of membrane potential? [1 mark]
The voltage (difference in electrical charge) across the plasma membrane.
What is the definition of resting potential? [1 mark]
The membrane potential of a cell not sending signals.
What is the ratio of ions pumped in and out via the sodium-potassium pump? [1 mark]
3 Na+ out : 2 K+ in
When does potassium leak occur? [1 mark]
At the resting potentials (K+ channels are open)
What is the Ek in a cardiac cell? [1 mark]
-90mV
What is the ENa in a neurone? [1 mark]
+62mV
What is the Nernst equation? [2 marks]
It measures the resting potential in membranes that are permeable to ONE ION.
What is the Goldman-Hodgin-Katz equation? [1 mark]
It measure the resting potential in membranes that are permeable to MULTIPLE IONS.
Which ion is the membrane more permeable to in hyperpolarisation? [1 mark]
Potassium (membrane potential becomes more negative)
Which ion is the membrane more permeable to in depolarisation? [1 mark]
Sodium (membrane potential becomes more positive)
What are the stages of an action potential in a neurone? [5 marks]
- Resting state
- Depolarisation
- Rising phase
- Falling phase
- Undershoot
What are the stages of an action potential in a cardiac cell? [5 marks]
- Diastole
- Depolarisation
- Rapid Na+ inactivation
- Plateau phase
- Rapid repolarisation
How does the strength of a stimulus affect the frequency of action potentials? [2 marks]
- Lighter stimulus = lower frequency
- Harder stimulus = higher frequency
How does the myelin sheath increase the speed of action potential propagation? [1 mark]
It contains the charge within the cell.
How does the diameter of the axon affect the speed of the action potential? [1 mark]
Larger diameter = speed of an action potential
