N2 nicotinic receptors are found in the brain, plus the autonomic and parasympathetic nervous systems [1]. Different subunits make up these two types of nicotinic receptor, which is why we consider them separately. Muscarinic receptors have a different mechanism of action.
Your body weight can regularly fluctuate, but the persistent, unintentional loss of more than 5% of your weight over 6 to 12 months is usually a cause for concern. You should pay particular attention if you experience other symptoms, such as tiredness, loss of appetite and a change in your toilet habits.
Potential causes of unexplained weight loss include: 1  Addison's disease (adrenal insufficiency). 2  Cancer. 3  Celiac disease. 4  Changes in diet or appetite. 5  Changes in sense of smell. 6  Changes in sense of taste. 7  COPD. 8  Crohn's disease.