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Questions and Answers
What is the effect of Ohm's Law on current in an electrical circuit?
What is the effect of Ohm's Law on current in an electrical circuit?
- Current is directly proportional to voltage and inversely proportional to resistance. (correct)
- Current is inversely proportional to voltage.
- Current is equal to resistance multiplied by voltage.
- Current is directly proportional to resistance.
In the context of ion substitution, which ion can replace Na+ in the example given?
In the context of ion substitution, which ion can replace Na+ in the example given?
- Choline+ (correct)
- K+
- Ca2+
- Li+
What characterizes the 'inward rectifier' phenomenon in ion channels?
What characterizes the 'inward rectifier' phenomenon in ion channels?
- They pass K+ better into the cell than out. (correct)
- They only allow Na+ to pass through the channel.
- They completely block any ion movement.
- They allow K+ to move out of the cell more easily.
What is typically ignored when measuring the resistance of an ionic solution in a pipette?
What is typically ignored when measuring the resistance of an ionic solution in a pipette?
What happens to the neurone during the 'holding' phase in the experiment?
What happens to the neurone during the 'holding' phase in the experiment?
What is the role of Na+/K+ ATPase in maintaining ionic balance?
What is the role of Na+/K+ ATPase in maintaining ionic balance?
What is the typical resistance of a seal formed in a neuronal unit?
What is the typical resistance of a seal formed in a neuronal unit?
What does rectification in ion currents refer to?
What does rectification in ion currents refer to?
What is the primary role of ion channels in neurons?
What is the primary role of ion channels in neurons?
Which equation is used to understand the equilibrium potential of ions across a membrane?
Which equation is used to understand the equilibrium potential of ions across a membrane?
What distinguishes ligand-gated ion channels from voltage-gated ion channels?
What distinguishes ligand-gated ion channels from voltage-gated ion channels?
What is the effect of the Na+/K+ ATPase on ion concentration across the membrane?
What is the effect of the Na+/K+ ATPase on ion concentration across the membrane?
During the generation of an action potential, what primarily causes the depolarization phase?
During the generation of an action potential, what primarily causes the depolarization phase?
What is the resting membrane potential typically around in nerve cells?
What is the resting membrane potential typically around in nerve cells?
What primarily shapes the behavior of a neuron when it is at rest?
What primarily shapes the behavior of a neuron when it is at rest?
What type of channels are described as “leak” channels?
What type of channels are described as “leak” channels?
What is the unit of conductance commonly used for neuronal recordings?
What is the unit of conductance commonly used for neuronal recordings?
How does the reverse of resistance relate to ion channels?
How does the reverse of resistance relate to ion channels?
Which type of experimental setup is used to study individual ion channels?
Which type of experimental setup is used to study individual ion channels?
During which mode can you inject current into a cell while measuring its response?
During which mode can you inject current into a cell while measuring its response?
What type of currents do we measure when using the classic two-electrode voltage clamp?
What type of currents do we measure when using the classic two-electrode voltage clamp?
What happens when extracellular solutions' ion concentrations are manipulated during experiments?
What happens when extracellular solutions' ion concentrations are manipulated during experiments?
What was a notable use for Xenopus oocytes in electrophysiological studies?
What was a notable use for Xenopus oocytes in electrophysiological studies?
What type of currents does the range from macro currents to pico-currents in electrophysiology cover?
What type of currents does the range from macro currents to pico-currents in electrophysiology cover?
What is the primary reason a smaller Na+ ion cannot pass through a K+ pore?
What is the primary reason a smaller Na+ ion cannot pass through a K+ pore?
Which type of ion channels is always open without a specific stimulus?
Which type of ion channels is always open without a specific stimulus?
What primarily regulates inward rectifier K+ channels?
What primarily regulates inward rectifier K+ channels?
What characterizes the selectivity of ion channels?
What characterizes the selectivity of ion channels?
Why might non-selective cation channels conduct more than one type of ion?
Why might non-selective cation channels conduct more than one type of ion?
What factors can influence the activity of potassium channels?
What factors can influence the activity of potassium channels?
What is a key function of leak potassium channels?
What is a key function of leak potassium channels?
How do gated channels differ from leak channels?
How do gated channels differ from leak channels?
What causes the resting membrane potential (RMP) to be negative inside the cell?
What causes the resting membrane potential (RMP) to be negative inside the cell?
What happens when the electrical field is strong enough to completely balance out the chemical gradient?
What happens when the electrical field is strong enough to completely balance out the chemical gradient?
What represents the potential at which the net flux of a particular ion is zero?
What represents the potential at which the net flux of a particular ion is zero?
Which of the following best describes what happens to K+ ions at resting membrane potential?
Which of the following best describes what happens to K+ ions at resting membrane potential?
What is the chemical driving force primarily related to in neurons?
What is the chemical driving force primarily related to in neurons?
At equilibrium potential, what happens to the electric and chemical driving forces?
At equilibrium potential, what happens to the electric and chemical driving forces?
Why is potassium often referred to as having 'leaky' channels in the context of resting membrane potential?
Why is potassium often referred to as having 'leaky' channels in the context of resting membrane potential?
What is the impact of a stronger electrical gradient on K+ ions as they exit the cell?
What is the impact of a stronger electrical gradient on K+ ions as they exit the cell?
Which ion is primarily associated with the establishment of the resting membrane potential in cells?
Which ion is primarily associated with the establishment of the resting membrane potential in cells?
What results from the simultaneous action of electrical and chemical gradients on K+ ions?
What results from the simultaneous action of electrical and chemical gradients on K+ ions?
Flashcards
Ion Channels
Ion Channels
Proteins in cell membranes that allow ions to pass through.
Resting Membrane Potential
Resting Membrane Potential
The electrical potential difference across a cell membrane when it's not firing.
Action Potential
Action Potential
Rapid change in membrane potential.
Electrophysiology
Electrophysiology
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I/V plot
I/V plot
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Nernst Equation
Nernst Equation
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Goldman Equation
Goldman Equation
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Equilibrium Potential
Equilibrium Potential
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Na+/K+ ATPase
Na+/K+ ATPase
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Leak Channels
Leak Channels
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Rectification
Rectification
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Ion Selectivity
Ion Selectivity
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Gated Channels
Gated Channels
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Patch Clamp
Patch Clamp
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Voltage Clamp
Voltage Clamp
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Conductance
Conductance
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Potassium Channels
Potassium Channels
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K2P Channels
K2P Channels
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Four-transmembrane domain channels
Four-transmembrane domain channels
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Cell-attached recording
Cell-attached recording
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Extracellular recording
Extracellular recording
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Two-pore domain potassium (K2P) channels
Two-pore domain potassium (K2P) channels
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Study Notes
Introduction
- Ion Channels are responsible for the maintenance of the resting membrane potential and the generation of action potentials
- The function of ion channels can be studied using electrophysiology and biophysical techniques
What are ion channels and how we study them?
- Ions cross plasma membranes via ion channels
- Ion channels are present in all cells
- Electrical activity of a neurone is determined by the flow of ions via ion channels
- I/V plots can be used to study the relationship between membrane potential and current flow through ion channels
- Nernst and Goldman equations are used to calculate the equilibrium potential of ions
- The resting membrane potential (RMP) is generated by the steady exit of K+ ions through specialized K+ channels
The Na/K ATPase
- The Na/K ATPase pumps 3 Na+ ions out of the cell for every 2 K+ ions pumped in
- The Na/K ATPase is mildly electrogenic, but does not contribute significantly to the generation of resting membrane potential
Generation of Resting Membrane Potential
- The resting membrane potential is generated by the efflux of K+ ions through leak channels
- Leak channels are open all the time and have moderate conductance
- K+ ions exit the cell following their concentration gradient, resulting in a negative membrane potential
The Equilibrium Potential
- The equilibrium potential (reversal potential) is the membrane potential at which the electrical driving force and chemical driving force are equal
- At the equilibrium potential, the net flux of the ion is zero
- The equilibrium potential impacts neuronal excitability, affecting the ability to generate action potentials
How we study Ion Channels Using Electrophysiology
- Electrophysiology allows study of ion channel activity at different scales
- Whole-cell patch clamp records currents from a single neuron
- Cell-attached recording records action potential frequency and patterns
- Voltage clamp allows controlling membrane potential and measuring current flow
- Patch clamp isolates currents from small groups of channels
- Extracellular recording studies action potentials from large groups of neurons
Conductance
- The slope of the IV plot can be used to calculate channel conductance
- Conductance is the inverse of resistance
- Conductance is measured in Siemens
Rectification
- "Inward rectifiers" pass K+ ions better into the cell than out of the cell
- This phenomenon is essential for the function of ion channels
- The mechanism of rectification is not completely understood
Ion Selectivity
- The selectivity of ion channels depends on the size and charge of the ions, and the amino acid residues lining the pore
- K+ channels are selective for K+ ions, while Na+ ions cannot pass through the pore
- Some ion channels are non-selective, conducting multiple ions
Types of Ion Channels
- "Leak" channels are open all the time, and have moderate conductance
- "Gated" channels open and close in response to a specific stimulus
- The activity of leak channels can change on a slow time scale
- Gated channels are responsible for fast electrical events in neurons
Potassium Channels
- Two main classes of K+ channels are responsible for resting membrane potential:
- Two-pore domain (K2P ) channels
- Four-transmembrane domain channels
- K2P channels are regulated by intracellular signalling mechanisms and are sensitive to various factors like pH and temperature
- Four-transmembrane domain channels are regulated by extracellular signalling molecules and are responsive to various environmental stimuli
- Potassium channels are essential for maintaining the resting membrane potential and regulating neuronal excitability
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Description
Explore the crucial role of ion channels in maintaining the resting membrane potential and generating action potentials in neurons. This quiz also delves into the study of ion channels using electrophysiology, including calculations involving Nernst and Goldman equations as well as the function of the Na/K ATPase.
