In a knee jerk, the afferent fibre is 0.55 m long and the efferent fibre is 0.55 m long…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
In a knee jerk, the afferent fibre is m long and the efferent fibre is m long. Both conduct at m/s. The signal crosses one chemical synapse in the spinal cord, which adds ms.
- How long does the impulse take in the afferent fibre?
- How long does it take in the efferent fibre?
- What is the total time of the reflex?
Need a reminder? The key ideaShow
A reflex is an involuntary response that needs a part of the CNS. The reflex arc has at least one afferent neuron, which enters the CNS by a dorsal root, and one efferent neuron, which goes to the effector. Time equals distance divided by speed, and each chemical synapse adds about . A body falling from rest covers .
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. Each fibre: m at m/s. One synapse: ms.
Plan. Find the time in each fibre, then add the synapse.
Step 1. Afferent fibre. s ms.
Step 2. Efferent fibre. The same: ms.
Step 3. Total. ms.
Answer: ms; ms; ms.
Check. The synapse is a small part of the time. A reflex with one synapse is among the fastest responses of the body.
Watch out. Do not forget the synapse, and do not count it twice.
More onHuman Body
Discussion (0)
Log in to join the discussion.
Loading…