Effector
Reflex action
gastrocnemius
Involuntary and reflex actions
Stretch Reflex
A reflex action is a fast, automatic response to a stimulus by an effector organ i.e. a muscle.
No it is not a reflex action
Fixator
Both require motor neurones to carry the nerve impulse to the effector in order for the muscle to contract carry out an action.
It's called the stretch reflex and involves muscle spindles which are sensorimotor organs located in skeletal muscle.
This particular reflex is autonomic as the affected muscle, constrictor pupillae muscle, is a smooth muscle and not under conscious control. Typically if you can consciously contract the muscle, any reflex associated with that muscle is somatic in nature.
If the muscle crosses a joint (most do), then the joint acts as a pivot.
autonomic reflex