Section 2: Autonomic Nervous System & Reflex Regulation
Just as the skeleton provides structure and support to enable general function of the body’s soft tissues, the human nervous system provides the structure and support necessary to enable reflexive function.
The Autonomic Nervous System
John Newport Langley in 1890 began to meticulously piece together the structure of the autonomic nervous system and to articulate its basic role in automatically managing the body’s unconscious processes. This is the basic structure now commonly known to engage the internal automatic reflex activity in the body. Langley shared the most important revelations regarding the nature of the autonomic system as he progressed, culminating in the formal publication of his findings in 1921, in a book that is still in publication today.
Regulatory Nature of the Reflex
In 1854 Claude Bernard was among the first to observe and demonstrate the systematic nature in which the body automatically maintains a constant milieu interieur (internal environment). While Langley continued to identify and articulate the structural nature of the autonomic nervous system, Walter Cannon uncovered two general response states present in the body. Cannon’s work demonstrated that when in a state of alarm, the body engages reflexes that prepare the body for fight or flight. Canon further demonstrated that when the alarm state dissipates, the body returns automatic reflex function to a normative state (later called rest and digest). By 1932, expanding on Bernard’s concept of milieu interieur and his own earlier work, Cannon confirmed that reflex actions work in a systematic nature through the autonomic nervous system to automatically maintain internal homeostasis. Finally, in 1936 Hans Selye revealed that alarm state reflexes can impose damage on the body if allowed to continue without intermittent normative states for recovery, the extent of which varies in direct proportion to the level of stress imposed on the body. Building on Cannon’s concept of homeostasis and the impact of an alarm state versus a normative state, Selye demonstrated that stress can be productive to a point, beyond which the alarm state reflexes engaged in the body begin to inflict biological damage.
Below are more in depth summaries of the contributions made by: