Stress As A Lifestyle

We often consider “stress” to be an emotive or psychological experience. While this may be true to a degree it is the physical fallout from prolonged exposure to distress, pain, or stressful living conditions that have the more detrimental impact on health and wellbeing, particularly in dogs.

Let us first consider the immediate physical and chemical processes involved in a stress reaction- primarily overseen by the nervous system. The subdivisions of the nervous system share the basic operational function of carrying electrical signals between the spinal cord, brain and a pathway of nerves which run throughout the body.

The peripheral nervous system (PNS) is our canine’s first responder in times of crisis. Unlike the central nervous system, which deals primarily with conscious decision making (save for the pain relief arc which we will return to in due course), the PNS is responsible for fear or stress based reactions. This system can then be further subdivided into the Somatic Division and Autonomic Nervous System, the latter of which contains the Sympathetic and Parasympathetic Divisions. Responsible for the activation and de escalation of the fear response respectively, both are continuously active within the nervous system. In a healthy dog who is at peace with their environment, the parasympathetic division works to maintain resting respiration and heart rates. After a stress response is complete, and the dog no longer faces the source of their pain/fear, this same division works to return the dog to its relaxed state. In contrast, the sympathetic division comes to the forefront to deal with the presence of a threat or stress event.

Before we go further into the physiology of such an event, it is important to consider that the following reactions are designed to be short term, infrequent biological processes. A dog who is presented with a stressful event or inhospitable environment will generally, with freedom of choice, seek to remove themselves from the situation in favour of more calm, suitable surroundings. The hormone floods, functionary in/decreases of the internal organs and metabolic changes experienced by the “stressed” dog are designed to enable him to flee (or defend themselves should the need arise) with greater efficiency.

Some of the changes called into action by the sympathetic division are familiar to us. The rush of adrenaline, increased blood pressure and heart rate, and pupil dilation will be fairly recognisable to anyone who has endured acute stress or shock themselves. Less obvious however, are the metabolic and digestive changes which occur within the canine body. While the liver releases glucose into the bloodstream, boosting the reserves of available energy, the kidneys and gastrointestinal tract are forced into a state of semi hibernation by the constriction of surrounding blood vessels. Digestion and urine production slow as a result. A full stomach would render the dog heavy and sluggish, and the energy usually expended by the digestive organs is commandeered to serve the fight or flight reaction. Likewise, the body considers the physical threat to be of greater immediate concern than potential biological or bacterial foes and the immune system is similarly powered down.

If the encounter plays out as it would in the natural world, with the aggressor either subdued or removed from the dog’s immediate environment, the parasympathetic division returns to the position of dominance within the Autonomic Nervous System. Immune and digestive systems are once again considered primary functions, heartbeat and respiration returns to resting levels and hormones are rebalanced. However, the response is not synchronised. The heart and lungs (being inherently rhythmical organs) may find their way back to calm within a few minutes, while the chemical and hormonal imbalances take far longer for the body to rectify. The stress response may not fully resolve itself for up to 72 hours, leaving the dog vulnerable to trigger stacking.

With awareness of these unseen biological processes let us now consider the long term, real world implications of raising or keeping a dog in a stressful environment.

Take for example the dog who fears the human who feeds them. Perhaps this owner has shown overt aggression towards the dog, or is simply following a punishment led training regime. In either case- as the human approaches, the ANS escalates the dog’s stress reaction and herein begins our problem. While the conscious areas of the brain and nervous system would normally welcome the arrival of fresh nutrition and move to ingest the food, the ANS has already prepared the body for flight. The digestive systems have been depressed, and remain so while in the presence of a perceived threat.

Consider now that this same dog is forced to live in the close company of their aggressor. Without sufficient time and space to allow the stress response to fully dissipate, the dog is unable to ingest the requisite nutrition to maintain a healthy physical condition. Without protein, muscle fibres begin to starve and cannot effectively heal if they are damaged. Without vitamins and fatty acids such as omega oils, skin and coat health declines. If the body is left in this state of want then malnutrition sets in, cells starve and deplete eventually leading to organ failure. At the same time the immune system is not fully functional, leaving the dog vulnerable to viruses and bacteria. Prolonged exposure to hormones such as adrenaline, cortisol and norepinephrine can overload the immune system completely.

It bears repeating that these processes are led by the unconscious areas of the nervous system. Our canine companions are, for the most part, far more connected to their primal physiology than their counterparts and these reactions cannot be rationalised into submission or overruled by conscious thought. Therefore in order to best serve the needs of domestic dogs, consideration of physiology, nutrition, health and behaviour should each inform the other- as demonstrated by the canine stress reaction.