33 Questions
What is the function of Tetrodotoxin (TTX) in relation to Na+ channels?
It blocks the pore of the Na+ channels
How does the structure of K+ channels differ from that of Na+ channels?
K+ channels have 4 subunits, while Na+ channels have 4 domains
What is the purpose of myelin in influencing conduction velocity?
To provide insulation and prevent the leakage of ions out of the axon
What happens during the refractory period of an action potential?
The inactivation of Na+ channels is terminated
What is the role of Saxitoxin in relation to Na+ channels?
It blocks the pore of the Na+ channels
What is the neural code for transferring information over long distances?
Frequency and discharge pattern
What is the term for the period during which a neuron cannot fire another action potential, no matter how strong the stimulus?
Absolute Refractory period
What causes the generation of an action potential?
Depolarisation of the membrane beyond a threshold
How can the frequency of discharge in the generation of action potential be influenced?
The amplitude of injected current
What is the purpose of patch-clamping in electrophysiology?
To record from a single ion channel at a time
When does the K+ current enter during the action potential?
At the end of the Rising phase and peaks at the start of the Falling phase
What is the mechanism of inactivation for Na+ channels?
« Ball and chain »
How does Tetrodotoxin (TTX) affect Na+ channels?
Blocks the pore of channels to Na+
What is the role of Batrachotoxin in relation to Na+ channels?
Blocks inactivation -> channel stays open
What is the function of Veratridine in relation to Na+ channels?
Lowers the activation threshold
How do K+ channels differ from Na+ channels in terms of inactivation?
Only Na+ channels inactivate
What is the typical conduction velocity of an action potential?
10m/s
Where does the orthodromic propagation of action potentials occur?
Towards the nerve terminals
What is the role of myelin in influencing conduction velocity?
Prevents the leakage of ions and allows saltatory conduction
What are the factors that contribute to electrotonic conduction underneath myelin?
Passive diffusion of Na+ ions in the longitudinal axis of the axon
Where is the initiation zone of action potentials in sensory neurons?
Nerve terminals (dendritic extremities)
What is the importance of the permeabilities of Na+ and K+ in the model of an action potential?
The permeabilities of Na+ and K+ determine the generation of action potentials.
How did Hodgkin and Huxley study the generation of action potentials?
They studied the giant axon of the squid and made a mathematical model.
What is the significance of the inactivation of Na+ channels in the reality of action potentials?
Inactivation of Na+ channels is crucial for the repolarization of the membrane by K+ channels.
What are the techniques used to observe the electrical activity of a neuron?
Recording electrode, current-clamp, and voltage-clamp.
How does the voltage-clamp circuit operate?
The voltage-clamp circuit injects current to maintain the membrane potential at a desired value.
What is the purpose of using a voltage-clamp?
The voltage-clamp is used to measure the Na+ and K+ current activated during an action potential.
Why does the Na+ current seem to inactivate after depolarization?
The Na+ current inactivates to allow for the sustained K+ current during depolarization.
What is the main difference between current-clamp and voltage-clamp techniques?
Current-clamp measures the membrane potential by injecting currents, while voltage-clamp measures the membrane current at a fixed potential.
Why is it important to use a voltage-clamp circuit in electrophysiology experiments?
The voltage-clamp circuit maintains a fixed membrane potential for accurate measurement of membrane current.
What is the role of the K+ current (IK) during an action potential?
The K+ current (IK) is sustained throughout the depolarization phase to repolarize the membrane.
What is the significance of the experiments of Hodgkin and Huxley in understanding action potentials?
The experiments of Hodgkin and Huxley revealed the complexity of action potentials and the necessity of channel inactivation.
What is the challenge with determining the membrane current (Im) at a specific membrane potential (Vm) without a voltage-clamp circuit?
The challenge is that ion channels can change membrane currents quickly, perturbing the membrane potential.
Test your knowledge on the ionic basis of action potentials, the sequence of channel openings and closings that generate each action potential, and how scientists can study the ionic current and the channel function of neurons. This quiz also covers topics from the readings in Bear, Chapter 4.
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