In the process of normal development, usually around 2.5 weeks after conception, the cells that will be muscles have started to develop, by 3 weeks the heart starts to beat, around 5 weeks cartilage forms to start bones, and by 6 weeks primitive brain waves can be registered and muscles start to contact. Now there is withdrawal of the head if you touch the mouth, and by 13 weeks there are several such instances all with specific movement patterns linked to specific sensations. These Primitive Reflexes are interwoven and inter-dependent on each other.
Integrate – obligatory motor responses diminish then evolve into choice.
Reflexes are expressed and used in combination until they have established the patterns and skills they are designed to create. A reflex is integrated when the obligatory movement or behavior pattern is no longer the only choice of response to the stimulus. It is integrated when there are options of more sophisticated, voluntary movement patterns and behavioural responses. This is often indicated by the ability to isolate muscle contraction & relaxation at will. This is skill development. It should also be noted that just because you can, does not mean you do. Sometimes the reflex pattern is useful - like in pitching a baseball. (ATNR)
Develop—Reflex Movement Repeats.
In utero mother’s movement and other things stimulate the baby and the reflexive movement is elicited and repeated over and over again. This provides the baby with more forms of stimulation critical for growth.
All reflexes have specific jobs. In general reflexes develop muscles, brain and nerve networks. They influence all the sensory apparatus and all bodily functions. The principle of what fires together, wires together is followed. (Hebbian theory) The reflexes train the brain/body systems to grow and function properly moving the embryo along the path to a running, jumping, self-actualizing being.
Life Cycle of a Primitive Reflex: Emerge, Develop, Integrate