Behaviour is a direct result of internal states and environmental influences.
Stress is often the basis for behaviour problems from aggression to anxiety based disorders. Stress is not just those things that make a dog anxious. It refers to anything internal or external that exerts some impact upon the dog, requiring it to take action in order to adapt to it. That means many things are stressful but some produce too much stress or too strong a negative impact upon the dog.
The nervous system is responsible for inputting and processing information and outputting behaviours. The nervous system is divided into different parts which serve different purposes. The sympathetic system causes dogs to be prone to emotional reactivity and the parasympathetic system causes dogs to be calmer and more able to adapt.
If the sympathetic system is more powerful in a dog he will be emotionally reactive and have a low stress threshold. If the parasympathetic system is more powerful in a dog he will be emotionally stable and have a higher stress threshold. Dogs that are sympathetically prone are more likely to develop behaviour problems.
The stress threshold is the upper limit point at which stress surpasses the dog's stress tolerance. Many dogs can handle high levels of stress without reaching their stress threshold while others cannot handle even small amounts of stress without becoming anxious.
Stress in general affects dogs but when stress surpasses the stress threshold a cascade of electrochemical reactions take place called a stress response. This level of stress is called over stress. It creates a chemical and functional disturbance. When a dog is acutely affected by stressful stimuli, a flood of chemicals surge into the brain. When this happens the dogs threshold for responding reactively or aggressively is lowered. The threshold for aggressive behaviour is lowered in dogs under stress.
If acute stress occurs adrenaline takes over and triggers the dog into action, mentally and physically. If chronic stress occurs, Norepinephrine (NE) (responsible for energy levels), Serotonin (regulates mood, pain and arousal levels) and Dopamine (involved in motor co ordination, attention and reaction time) become depleted. A dog suffering an over stress response will express the consequences in some of the following ways:
Rapid panting, lack of focus or attention, sweaty paws, yawning, hyperactivity, increased urination and defecation, vomiting and diarrhoea, stretching, shaking as if coming out of water, confusion, self-mutilation, excessive grooming, sleeping excessively, excessive thirst, obsessive-compulsive behaviour, overly reactive, stiff muscles, shivering, skin disorders
Stress Reduction: The aim of stress reduction is to help return the chemical imbalance in the dog's brain to normal. Management of the stressors is essential along with relaxation/down time, nutritional intervention, mental stimulation, exercise and coping strategies. It is important to remember that a dog simply cannot learn while it is over stressed.