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Questions and Answers
What is the primary function of the phospholipid bilayer in the neuronal membrane?
What type of charge do cations carry?
Which feature of water contributes to its function as a solvent in biological systems?
Which type of compound typically does not dissolve in water?
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What is the resting membrane potential primarily dependent on?
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What is the primary reason for the resting membrane potential being negative?
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What role does the sodium-potassium pump (Na+/K+ ATPase) play in maintaining the resting membrane potential?
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Which statement accurately describes membrane permeability at rest?
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What factors contribute to the generation of resting membrane potential?
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How does the resting membrane potential relate to ion channel distribution?
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What is resistance in the context of electrical charge movement?
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According to Ohm's law, how is current related to voltage and resistance?
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What phenomenon is described by the need for tiny ion concentration changes to cause large changes in membrane potential (Vm)?
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What is the equilibrium potential (Eion) in the context of ion movement?
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What happens when there is no net current flow between two points?
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What primarily determines the rate of ion movement across a neuronal membrane?
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Which ion is more concentrated on the inside of a typical neuronal cell?
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What defines a conductor in electrical terms?
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What is the primary function of the sodium-potassium pump?
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What occurs when opposite charges are kept separated across a membrane?
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What is the resting membrane potential in neurons?
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What does the Nernst equation calculate?
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What condition is NOT considered when calculating the equilibrium potential using the Nernst equation?
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What is the role of membrane protein channels in neuronal function?
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If there is no voltage across a membrane, what is the result concerning ionic movement?
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How much ATP can the sodium-potassium pump consume in the brain?
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How does the presence of K+ channels in the neuronal membrane affect membrane potential?
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What has the highest concentration outside a typical neuronal cell?
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What is the primary mechanism by which ions diffuse when gated channels are open?
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What is significant about the potassium channels in relation to resting membrane potential?
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What discovery is associated with the Shaker potassium channel?
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Which structure within potassium channels is crucial for their selective permeability?
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What effect does increased extracellular K+ concentration have on membrane potential?
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What prestigious award did MacKinnon receive for his work on K+ channels?
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Which statement accurately describes the number of subunits in potassium channels?
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To what type of genetic disorders are mutations in specific K+ channels linked?
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Study Notes
Neuronal Membrane Overview
- Neuron communication relies on electrical signals known as action potentials, requiring a baseline resting membrane potential.
- Resting membrane potential is the electrified state of neuronal cells, vital for action potentials to occur.
Key Components of Neuronal Membrane
- Cytosol and extracellular fluid primarily consist of water, a polar solvent essential for dissolving ions.
- Ions are charged atoms or molecules; cations have a positive charge, while anions have a negative charge.
- The phospholipid bilayer forms a barrier that isolates neuronal cytosol from extracellular fluid, distinguishing hydrophilic (water-soluble) and hydrophobic (water-insoluble) substances.
Electrical Principles in Neuron Function
- Ohm’s law explains the relationship between current (I), conductance (g), and potential (V): I = gV.
- Voltage measures the potential energy generated by separated charges, with net charge differences leading to varying voltages.
- Current signifies the flow of electric charge between two points, dependent on voltage and resistance.
Membrane Potential Dynamics
- Neurons maintain a resting membrane potential that can change rapidly compared to other cell types.
- The energy required to separate opposite charges across membranes contributes to potential energy.
Ionic Basis of Resting Membrane Potential
- The equilibrium potential (Eion) depicts no net ion movement across membranes without channel proteins.
- The presence of K+ channels leads to ionic flow down concentration gradients, altering charge/voltage across the membrane.
- The Nernst equation calculates equilibrium potentials, accounting for ion charge, temperature, and concentration ratios.
Ion Distribution and Movement
- Ion concentrations vary, with K+ primarily inside and Na+ along with Ca2+ predominantly outside the cell.
- Sodium-potassium pumps (3 Na+ out, 2 K+ in) actively transport ions against their gradients, consuming up to 70% of brain ATP.
Membrane Permeability
- Neuronal membranes are selectively permeable, with K+ permeability 25 times greater than Na+ due to more leakage channels.
- More potassium diffuses out than sodium diffuses in, contributing to the negative internal charge and establishing resting membrane potential.
Role of Ion Channels
- Membrane permeability relies on distinct ion concentrations, channel presence, and ion-specific conductance.
- Gated channels allow ion diffusion along concentration and electrical gradients; potassium channels are central to resting membrane potential regulation.
- Various types of K+ channels exist, such as the Shaker potassium channel, identified in fruit flies.
Potassium Channel Structure and Function
- Potassium channels consist of four subunits, forming a selective filter for K+ ions through the pore loop area.
- MacKinnon's research on K+ channels won the 2003 Nobel Prize, revealing that specific mutations lead to neurological disorders.
Importance of Extracellular K+ Concentration
- The resting membrane potential closely aligns with EK due to high K+ permeability, making it sensitive to extracellular K+ changes.
- Elevated extracellular K+ levels can cause membrane depolarization, significantly affecting neuronal activity.
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Description
This quiz explores the key components of the neuronal membrane, focusing on ion movements and the resting membrane potential. Understand the cellular electricity involved and the important ion channels that facilitate neuronal communication through action potentials.