Neural signalling: impulses and synapses
| English | 中文 | Pinyin |
|---|---|---|
| action potential/ˈækʃn pəˈtenʃl/ | 动作电位 | dòng zuò diàn wèi |
| synapse/ˈsɪnæps/ | 突触 | tū chù |
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?
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.
Match each technical term to its precise meaning.
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?
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.
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.
The result is 60 Hz. 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.
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: 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.
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.
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.
A brief propagating change in membrane potential: write the technical term.
action potential means A brief propagating change in membrane potential.