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PhysioEx Ex3Acvty4
volted gated Na+ channels
| Question | Answer |
|---|---|
| How is action potential generated from voltage gated Na+ channels? | When they open in sufficient numbers |
| When do the voltage-gated sodium channels open? | when the membrane depolarises |
| What happens when the sodium channels open? | It allows Na+ions to diffuse into the cell and move down their electrochemical gradient |
| Describe tetrodoxotin | It is a chemical found in putter fish and it is extremely poisonous |
| Describe lidocaine | A chemical used to block pain in dentistry and minor surgery |
| What 3 things can reduce the likelihood of an action potential? | TTX, lidocaine & increasing the leak of K+ from a cell |
| What does lidocaine do to voltage-gated Na+ channels? How does the effect of lidocaine differ from the effect of TTX? | Lidocaine blocks the diffusion of Na+ through voltage-gated Na+ channels. The difference between TTX and lidocaine is that lidocaine's effect is reversible. |
| What does TTX do to voltage gated Na+ channels? | TTX blocks the diffusion of Na+ through voltage-gated Na+ channels. This blockage is irreversible. which is why it is not used in dental procedures |
| If a nerve, rather than an axon, had been used in the lidocaine experiment, the responses recorded at R1 and R2 would be the sum of all the action potentials (compound). Would the response at R2 after lidocaine application necessarily be zero? Y or y not? | With a compound action potential, the results would not necessarily be zero because some axons could remain unaffected. |
| When voltage-gated Na+ channels between R1 and R2 are blocked with TTX, an action potential is still recorded at R1 because? | The voltage-gated Na+ channels between the stimulus and R1 are unaffected by the TTX. |
| What happens at recording electrodes when lidocaine is applied b/w R1 and R2? | Fewer action potentials are recorded at R2 which means lidocaine blocked the responses at R2 |
| Pain-sensitive neurons (called nociceptors) conduct action potentials from the skin or teeth to sites in the brain involved in pain perception. Where should a dentist inject the lidocaine to block pain perception? | Lidocaine should be applied to the receptors to prevent the generation of an action potential that would lead to the perception of pain. |
| With a slower timescale, how will the appearance of the action potentials generated at R1 and R2 appear to be? | be compressed in time but have the same peak value of response |
| n the control, the amplitudes of the action potentials at R1 and R2 are the same. Which of the following explains this? (3) | The action potential is an all or none event, there are voltage gated Na+ channels all along the axon and action potentials propagate or remake themselves at each point along the axon |
| Blocking the voltage-gated Na+ channels between R1 and R2 with TTX blocks | The propagation of the action potential from R1 to R2. |
| When voltage-gated Na+ channels between R1 and R2 are blocked with TTX, an action potential is still recorded at R1 because | The voltage-gated Na+ channels between the stimulus and R1 are unaffected by the TTX. |
| Puffer fish must be prepared carefully and properly before they can be eaten. Eating puffer fish can cause numbness of the lips, probably because | action potentials from sensory neurons in the lips are blocked. |
Created by:
meunid