Pain is one of the most common reasons why patients reach out for medical care. Pain tolerance varies from patient to patient. Pain has sensory and emotional building blocks that are categorized as acute or chronic pain. Acute pain is usually associated with anxiety and increased activity of the sympathetic nervous system. Examples include tachycardia, increased blood pressure, increased respiratory rate, dilated pupils, and diaphoresis. Acute pain is often a response to tissue injury, which leads to the sensory nerve fibers peripheral pain receptors to activate. While acute pain is associated with the sympathetic nervous system, chronic pain is not and is related with vegetative signs and depressed feelings. Examples of vegetative signs include
