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.
Alopecia Areata â Stress can cause a condition called alopecia areata, an autoimmune condition that causes the immune system to attack and destroy healthy tissue, including hair follicles. Hair may fall out in patches, resulting in bald spots. Illness, pregnancy, and trauma are often a cause of this type of balding.