Neural signalling: impulses and synapses
도입됨| English | 의미 |
|---|---|
| action potential/ˈækʃn pəˈtenʃl/ | 작동전위 |
| synapse/ˈsɪnæps/ | 시냅스 |
What would explain this observation?
- A stronger stimulus can increase impulse frequency while each action potential 动作电位 remains a similar size.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- An action potential is a brief change in membrane potential involving voltage-gated ion channels. Depolarization followed by repolarization propagates along a neuron. At a chemical synapse 突触, transmitter release can alter the next cell membrane potential.
- action potential: A brief propagating change in membrane potential; synapse: A junction for communication between cells.
How can stimulus intensity affect an all-or-none signalling system?
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Each action potential is all-or-none with fixed amplitude, so intensity is coded by how often impulses fire and how many neurons are recruited. Amplitude cannot grow, and removing ion gradients would abolish signalling.
Match each technical term to its precise meaning.
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Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- The all-or-none principle applies to an individual action potential. Stimulus information can be encoded by frequency and recruitment. Myelination permits saltatory conduction between nodes rather than making ions move freely through myelin.
- Interpret supplied voltage-time traces and compare time intervals. Identify threshold, rising phase and recovery before explaining ions. Use classroom models rather than electrical stimulation of people.
Which two habits make the investigation or model in this case more defensible?
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Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: 30 impulses occur in 0.50 s. Frequency = count/time = 30/0.50 = 60 Hz. This is impulse frequency, not an estimate of propagation speed.
24 impulses occur in 0.40 s. Find impulse frequency. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
24 impulses occur in 0.40 s. Find impulse frequency.
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The result is 60 Hz. Known: 24 impulses in 0.40 s. Use frequency = count / time. Frequency = 24/0.40 = 60 Hz. This is firing frequency, not conduction speed along the axon.
Check the conclusion and its limits
- A neurotransmitter diffuses across the synaptic cleft; an action potential does not jump intact through the liquid gap. Excitatory input does not guarantee the postsynaptic cell reaches threshold.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
A stronger stimulus always makes each action potential larger. This claim is false: Action potentials are all-or-none: once threshold is reached, the impulse has a fixed size set by the ion gradients. A stronger stimulus raises the frequency of impulses, not their amplitude.
Neural signalling: impulses and synapses: The all-or-none principle applies to an individual action potential. Stimulus information can be encoded by frequency and recruitment. Myelination permits saltatory conduction between nodes rather than making ions move freely through myelin.
A stronger stimulus always makes each action potential larger.
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Action potentials are all-or-none: once threshold is reached, the impulse has a fixed size set by the ion gradients. A stronger stimulus raises the frequency of impulses, not their amplitude.
A brief propagating change in membrane potential: write the technical term.
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action potential means A brief propagating change in membrane potential.