Acetylcholine is released from a presynaptic neuron into the synaptic cleft. Once in the synaptic gap, acetylcholine can: - Bind to presynaptic receptors: presynaptic activation or inhibition leads to automodulation of the presynaptic cholinergic neuron.
When welts are a sign of a medical problem, they are usually accompanied by other symptoms which provide clues to the problem. Physical trauma such as a blow can cause a welt, and welts can also be caused by allergic reactions, infections, injections, insect bites, and skin reactions, in very sensitive people. For example, in people with dermographism, even a gentle touch to the skin can cause a welt to emerge.
Systemic lupus erythematosus (SLE), or lupus, is an autoimmune systemic disorder, which affects the joints, skin, and practically any organ in the body. Fibromyalgia affects the muscles causing pain, tender points, and extreme fatigue, and can contribute to anxiety or depression. Both lupus and fibromyalgia are difficult to diagnose, and many patients with fibromyalgia are often wrongly diagnosed with lupus and vice versa.