Questions and Answers
What is the term for changes in the membrane potential that cannot spread far from the site of stimulus?
What is created by any stimulus that opens a channel?
Graded potential
The degree of depolarization decreases with distance away from the depolarization site.
True
Graded potentials tend to propagate without any decrease in strength.
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What is the characteristic of graded potential regarding sodium ions?
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In order for a neuron to send a message, what must occur at the axon hillock?
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Graded potentials can trigger exocytosis and glandular secretion.
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What is another term for action potentials?
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Action potentials contain refractory periods.
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What principle do action potentials follow?
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Graded potentials are always depolarizing.
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Action potentials require depolarization to threshold before they can begin.
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What does the amount of depolarization or hyperpolarization depend on?
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What is true about action potentials concerning stimuli?
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Graded potentials can propagate along the entire membrane surface without decrease in strength.
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Refractory periods do not occur with graded potentials.
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Where do graded potentials occur?
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Action potentials occur only in excitable membranes of specialized cells like neurons and muscle cells.
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Study Notes
Graded Potentials
- Changes in membrane potential that occur locally and do not propagate far from the site of stimulus.
- Result from the opening of ion channels, leading to local depolarization or hyperpolarization.
- The extent of depolarization diminishes with distance from the stimulus site.
- Tend to diminish over time, often referred to as fizzling out.
- Sodium ions contribute to partial depolarization of the cell.
- Graded potentials sum together; for a neuron to transmit a message, the axon hillock must reach a specific threshold voltage.
- Can initiate exocytosis and trigger glandular secretion.
- Lacks a definite threshold value; any stimulus can cause varying degrees of change in membrane potential.
- Passive spread occurs from the site of stimulation, meaning the effect weakens as it moves away.
- Effects on membrane potential diminish with increased distance from the stimulus site.
- Occur in most plasma membrane types, not limited to excitable tissues.
Action Potentials
- Commonly referred to as nerve impulses.
- Operate under the all-or-none principle meaning once the threshold is reached, action potentials occur with the same magnitude.
- Involve refractory periods which ensure unidirectional propagation and limit the frequency of firing.
- Always involve depolarization, leading to the rapid rise in membrane potential.
- Require a depolarization to threshold before initiation, providing a necessary prerequisite for action potentials.
- All stimuli exceeding the threshold produce identical action potentials, regardless of the stimulus strength.
- Potential at one site can depolarize adjacent sites, contributing to a wave-like propagation along the nerve.
- Propagated along the entire membrane surface without any decrease in strength, maintaining signal integrity over distance.
- Refractory periods are characteristic of action potentials, preventing immediate re-firing.
- Occur exclusively in excitable membranes, such as those of neurons and muscle cells, which are specialized for rapid signaling.
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Explore the differences between graded potentials and action potentials with these flashcards. Each card presents key terms and definitions that help elucidate the characteristics and behaviors of these essential neural processes.
