The third category, in general, referred to as crying or weeping, is increased lacrimation due to strong "Emotional stress", "Anger", "Suffering", "Mourning", or "Pain". It also occurs during the brains "Fight-or-flight response". This practice is not restricted to negative emotions; many people cry when extremely happy. In humans, emotional tears can be accompanied by reddening of the face and sobbing — cough-like, convulsive breathing, sometimes involving spasms of the whole upper body. Tears brought about by emotions have a different chemical make-up than those for lubrication; emotional tears contain more of the protein-based hormones "Prolactin", "Adrenocorticotropic hormone", and "Leucine""Enkephalin" (a natural painkiller) than basal or reflex tears. The Limbic system is involved in production of basic emotional drives, such as anger, fear, etc. The limbic system, to be specific, the hypothalamus, also has a degree of control over the autonomic system. The parasympathetic branch of the autonomic system controls the lacrimal glands via the neurotransmitter Acetylcholine through both the Nicotinic and Muscarinic receptors. When these receptors are activated, the lacrimal gland is stimulated to produce tears.