Question

Which afferent muscle spindle nerve fibres transmit a large burst of APs during the dynamic phase of muscle stretching and what property of these nerves allows this?

a) Ia fibers; high sensitivity to velocity changes
b) II fibers; high sensitivity to muscle length
c) Ib fibers; low sensitivity to velocity changes
d) Gamma fibers; low sensitivity to muscle length

Answer 1

During the dynamic phase of muscle stretching, Ia fibers transmit a large burst of action potentials due to their high sensitivity to velocity changes.

Step-by-step explanation:

The afferent muscle spindle nerve fibers that transmit a large burst of action potentials (APs) during the dynamic phase of muscle stretching are the Ia fibers, which have a high sensitivity to changes in velocity. This property allows them to rapidly respond to the rate at which a muscle is being stretched, which is vital for initiating quick reflexes that help prevent muscle damage from overstretching. The dynamic phase is when the muscle is being stretched and the velocity of stretching is changing, which is precisely when these fibers are most active.