what does this trigger?

### The "stretch reflex", causing the muscle motor unit to fire, in turn causing contraction of the stretched muscle

## Step1: Identify the Trigger### When a muscle is stretched, it triggers a response in the nervous system.## Step2: Activation of the Stretch Reflex### This stretching activates the "stretch reflex," which is an automatic response to muscle stretch.## Step3: Firing of the Muscle Motor Unit### The stretch reflex causes the muscle motor unit to fire, meaning the nerve and muscle fibers connected to it activate.## Step4: Muscle Contraction### The firing of the muscle motor unit leads to the contraction of the stretched muscle, helping to resist the stretching force.