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.
Urticaria, or hives, is a dermatologic condition that causes swollen, red bumps on the skin. Also known as weals, these bumps usually appear rapidly and can be anywhere on the body, causing your skin to itch, burn, or sting. The itching is often the worst part and once you've gone through it, the idea of reliving the experience is unpleasant.