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.
Top 10 facts about the world. Many conditions can cause raised, red skin welts that may or may not itch, including allergies, hives, insect bites, and infection somewhere in the body. The welts, sometimes called skin wheals, usually go away in a few days but can be uncomfortable while on the surface of the skin.