Chapter 4 Flashcards
Electrical potential/charge
: the ability to do work with stored electrical energy. Requires a difference in the concentration of electrons between two points.
Volts
The units of measurement for electrical potential/charge.
Current
The flow of electrons from an area of high concentration to an area of low concentration through a conductor
Insulator
A substance whose electrochemical properties make it a bad medium for the movement of electrons
Conductor
A substance whose electrochemical properties make it a good medium for the movement of electrons
Who stuck charged metal on frog legs?
Luigi Galvani
What is the resting membrane potential charge?
Between -65mV (excess of negative charge on the inside of cell membrane)
Who measured nerve conduction velocity?
Herman von Helmholtz measured nerve conduction velocity as ~30 meters/second
What are the ion concentrations at resting membrane potential?
Na+: High outside the cell, low inside Cl-: High outside the cell, low inside K+: High inside the cell, low outside Proteins (A-): High inside the cell, low outside
What is necessary to achieve the gradients required for resting membrane potential?
- Proteins (A-) stuck inside the cell - Open K+ Channels “leak channels” - Closed Na+ Channels (don’t need them to have potential, but if you have them, they need to be closed to have a resting membrane potential) - Na+/K+ pump to maintain the imbalance
Hyperpolarization
Moving the membrane potential more negative than the resting membrane potential.
Depolarization
Moving the action potential more positive than the resting membrane potential. In action potentials, it’s dominated by the rapid influx of sodium (Na) through voltage-gated sodium channels.
Action potential
A transient reversal of a membrane potential is an action potential (a change in voltage across time)
What makes an action potential begin?
The axon hillock decides whether to fire or not. The axon hillock going from -65mV to -40 mV (threshold) makes the action potential begin.
Repolarization
In action potentials, dominated by the delayed potassium efflux from the cell while sodium channels close.
absolute refractory period
no new action potentials can be fired.
relative refractory period
action potentials are possible, but harder to trigger.
What makes pores open in the membrane?
pores are opening due to the cation amino acids present in the pore, it is a passive process.
Where are voltage gated Na+ channels found in the cell?
The voltage gated channels for Na+ are ONLY found in the axon - they are not found in the dendrite and the soma.
Big picture of action potentials
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What happens to voltage-gated Na+ channels after an axon potential
Na+ channels are blocked by their ball-and-chain shortly after they open, they do not open until they reach resting potential again.
How do Na+ K+ pumps work?
They pump out three Na+ for two K+
