Dear all,
We know that each reflex involves a time delay between the stimulus and the reaction. This time delay is called reflex latency and It consists of three components:
I want to model the reflex latency of the stretch and miotatic reflexes in human upper limb (In particular, I'm interested in biceps, triceps and brachialis muscles).
In your opinion which are the best values for Ta , Tc and Te?
After reading different papers and books, my ideas is that good values could be:
Ta= 10 msec;
Te= 10 msec;
Tc= 0.5 msec if we hypothesize that the motoneuron has just one synapse.
So, the stretch reflex latency is equal to 20.5 msec and the golgi tendon reflex latency is equal to 21 msec
Dear Antonio,
These values will depend on the age and the size of the subject. You may be able to find axonal conduction velocity values for each component in literature and then measure the distance for your individual subject and calculate it.
You also need to consider differences between slow and fast twitch units. Also previous injuries and genetic make up of the individual may have effects on the conduction velocities. As you may already know that with aging fast-twitch units are declining.
best wishes,
Refik
Dear Refik,
thank you for your clear answer.
Can you suggest me papers in which mean values for axonal conduction velocity, distance from muscle of the upper arm to spinal segment are reported?
Dear Antonio,
I dont know any specific references, but I would recommend you to check work from Simon Gandevia from UNSW, Sydney Australia. He and his collegues have 100s of electrophysiological studies in humans. If you go through their papers you may find alot of usuful information.
Best wishes,
Refik
Ha - this was the subject of my PhD thesis! I analyzed the latency of not only the H reflex (stretch reflex) but also the 'long-loop' reflex that ascends to the cortex and back. This analysis determined the latencies due to sensory and motor nerve conduction and the central delay. However, this was carried out for the thenar muscles of the hand, not the arm muscles but it should serve as a guide. The citation is:
Stanley, E.F.# Reflexes evoked in human thenar muscles during voluntary activity and their conduction pathways. J. Neurol. Neurosurg. Psych., 41 (1978) 1016-1023. Message if you want a copy.
Later I did it also for the rat: Stanley, E.F.# Sensory and motor nerve conduction velocities and the latency of the H reflex during growth of the rat. Exp. Neurol., 71 (1981) 497-506.
Of course the central delay of the H reflex is very short indeed since it is monosynaptic.
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