Lecture 2- Voltage Gated Na+ Channel Flashcards
(108 cards)
What are 2 electrodes inserted into?
Squid giant axon
What are the 2 types of electrodes?
- Recording voltage difference across membrane
2. Intracellularly injecting current
What are electrodes connected to?
Feedback circuit
What does feedback circuit do?
Compare the measured voltage across the membrane with voltage desired by the experimenter
What happens if 2 values differ?
Current is injected into axon to compensate for the difference
What is continuous feedback cycle?
Voltage is measured and current injected effectively clamps the membrane at a voltage
What happens in a voltage clamp?
The membrane potential is maintained constant or held at a command potential
What is the purpose of making axons bigger?
Conduct impulses more quickly
What does amplifier receive?
Input from inside/outside of axons
What does amplifier detect?
Changes in potential across membrane
What does Na+ channels confer?
Excitability
What depends on sodium channel ?
Nerve cells
Muscle cells
Heart cells
What is present at internode?
Transmembrane current
What current is present at node?
Inward current
What allows activation of the next node?
Current that flows in a circuit
What are necessary to propagate impulse?
Local circuit
What do Na+ channels exhibit?
Voltage- dependent activation
Clamp steps
Start from a negative baseline
Step more positive
What does voltage clamp allow?
Separation of membrane ionic and capacitance currents
What is the whole cell patch clamp arrangement?
Studying the properties of small patch of membrane
What is the process of whole cell patch clamp arrangement?
A glass pipette with a very small opening is used to make tight contact with a very small area of neuronal membrane
2. small suction happens to back of pippete
3. Seal between pipette and membrane become so tight - no ions can flow between pipette and membrane
4. All ions gang flow when single ion channel open flow into pipette
5.
How is the electrical current measured?
Electronic amplifier connected to the pippete
What is depolarising pre-pulse?
Electrical stimulus that causes potential difference measured across membrane to become more positive or less negative
What happens when DPP is short?
Threshold will decrease