Weak Stimulus to a Neuron
Lesson notes
Overview
Below threshold a neuron does not fire. This topic is rated beginner and is number 67 of 110 in Biology. Core ideas and first intuitions. No prior knowledge needed.
What you are seeing
The panel above shows a living system animated over time. The animation is drawn live from the model, so everything you see responds to the sliders. Press Space to pause, use Restart to replay from the start, and change the speed to slow down quick events.
In depth
A neuron fires only if the stimulus depolarises the membrane past a threshold, about −55 mV. A weak, sub-threshold stimulus causes a small local change that fades away and no action potential results. Weak inputs can still add together, either in space from several synapses or in time from rapid repeated ones, and may then reach threshold. This integration lets neurons act as decision-makers, summing excitatory and inhibitory signals.
Reading the relationship
The expression "sub-threshold" is a compact summary of the idea. It uses the symbols s, u, b, t, h, r; name what each one stands for before you start. Then use the sliders to see how changing one quantity changes the others.
A guided exploration
1. Run the animation once with the default settings and describe in words what happens. 2. Change one slider at a time and note which quantity responds most. 3. Push each slider to its extreme and decide whether the result still makes sense.
Try this
Start by only moving one slider at a time. Say aloud what you expect, then check.
Common pitfalls
Biological processes are rarely all-or-nothing. Look for the feedback, the timing and the exceptions, rather than learning a single fixed sequence by heart.
How it connects
It builds on “Slow Predator–Prey Cycle”, the topic before it in Biology. Once you are comfortable, continue with “Strong Stimulus to a Neuron”.
Why it matters
Biology shows how living things are built and how they work, grow, inherit traits and adapt.
Where you might use it
- Revising “Weak Stimulus to a Neuron” before a class, exam or certification
- Understanding inherited conditions, medicines and how the body responds to disease
- Working in farming, conservation and food production, where populations and genes matter
- Following news about vaccines, genetic testing and climate effects on wildlife
Frequently asked questions
What is Weak Stimulus to a Neuron?
Below threshold a neuron does not fire. It is a beginner topic in Biology.
How do I use the Weak Stimulus to a Neuron simulation?
The panel at the top shows a living system animated over time. Move the sliders one at a time, then press Space to pause the animation and look closer.
What does the formula mean?
The expression sub-threshold packs the idea into symbols. Name each symbol first, then change one quantity with the sliders and see which others respond.
Who is this topic for?
Core ideas and first intuitions. No prior knowledge needed. If the quiz feels hard, reread the lesson notes and try the previous topic first.
What should I learn before this?
Start with “Slow Predator–Prey Cycle”, the previous topic in Biology. Each topic in a subject builds on the ones before it.
How do I track my progress?
Press “Mark as learned” on this page. Progress is stored only in this browser and is never sent anywhere. The Browse page can show topics you have learned or still need to learn.