Questions and Answers
Where in the neuron is an action potential initially generated?
axon hillock
The depolarization phase of an action potential results from the opening of which channels?
voltage-gated Na+ channels
The repolarization phase of an action potential results from __________.
the opening of voltage-gated K+ channels
Hyperpolarization results from?
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What is the magnitude (amplitude) of an action potential?
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What type of conduction takes place in unmyelinated axons?
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An action potential is self-regenerating because?
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Why does regeneration of the action potential occur in one direction?
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What is the function of the myelin sheath?
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What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?
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In which type of axon will the velocity of action potential conduction be the fastest?
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The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.
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During depolarization, which gradient(s) move(s) Na+ into the cell?
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What is the value for the resting membrane potential for most neurons?
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The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?
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The concentrations of which two ions are highest outside the cell?
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Study Notes
Neuron Function and Action Potential Overview
- Action potentials are initially generated at the axon hillock of a neuron.
- The depolarization phase occurs due to the opening of voltage-gated Na+ channels, allowing sodium ions to flow into the neuron.
- Repolarization phase is triggered by the opening of voltage-gated K+ channels, facilitating potassium ions’ exit from the cell.
- Hyperpolarization happens because of the slow closing of voltage-gated K+ channels, leading to an increase in negativity within the neuron.
Action Potential Characteristics
- The magnitude of an action potential is approximately 100 mV, highlighting the rapid voltage change during the event.
- Continuous conduction occurs in unmyelinated axons, meaning every segment of the axon depolarizes sequentially.
- Action potentials are self-regenerating; depolarizing currents from Na+ influx propagate along the axon, triggering potential generation in adjacent segments.
- Regeneration of action potentials occurs in one direction due to inactivation of Na+ channels in previous segments.
Role of Myelin and Axon Structure
- The myelin sheath serves to increase conduction speed of action potentials from the initial segment to axon terminals.
- Action potential conduction velocity is fastest in myelinated axons with the largest diameter due to reduced capacitance and faster propagation.
Ion Movements and Membrane Potential
- Neuron membranes at rest show high permeability to K+ and low permeability to Na+, essential for maintaining resting membrane potential.
- During depolarization, both electrical and chemical gradients drive Na+ ions into the cell, contributing to the rapid change in voltage.
- The resting membrane potential for most neurons is around -70 mV, an important baseline for neuronal activity.
- The Na+-K+ pump actively transports Na+ out of the cell and K+ into the cell, counteracting ion leakages and maintaining the concentration gradients.
- The highest concentrations of ions outside the cell are Na+ and Cl-, crucial for establishing resting potential and action potential dynamics.
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Test your knowledge of Chapter 11 in Neuroscience with these flashcards. Explore key concepts such as the action potential, ion channels, and the phases of neuron signaling. Perfect for reinforcing your understanding and preparing for exams.
