A signal travels along a path in three steps…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A signal travels along a path in three steps. A sensory fibre of m conducts at m/s. The signal then crosses a synapse, passes a very short interneuron, and crosses a second synapse. Each chemical synapse adds a delay of ms. Last, a motor fibre of m conducts at m/s. Ignore the time in the interneuron.
- How long does the signal take in the sensory fibre?
- How long does it take in the motor fibre?
- How much time is lost at the synapses?
- What is the total time?
Need a reminder? The key ideaShow
Time equals distance divided by speed. A thin non-myelinated fibre conducts at about , and a thick myelinated fibre at about to . An electrical synapse passes current directly. A chemical synapse uses a neurotransmitter, and it adds a delay of about . The new potential may be excitatory or inhibitory.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Sensory: m at m/s. Motor: m at m/s. Two synapses, ms each.
Plan. Find the time of each part, then add.
Step 1. Sensory fibre. s ms.
Step 2. Motor fibre. s ms.
Step 3. Synapses. ms.
Step 4. Total. ms.
Answer: ms; ms; ms; ms.
Check. The synapses take only a small part of the time, but each chemical synapse adds a delay.
Watch out. Do not forget the synapses. Without them the sum is ms.
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