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What physical changes can occur in the body during a painful experience?

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How does the human body perceive and respond to pain? — pain Learn how the human body senses pain and reacts to it.

Pain serves as a vital warning system, and the body undergoes significant physiological changes when experiencing it. These responses are often part of the fight-or-flight response, an acute reaction to threats or injury that prepares the body to react or retreat.1

Physiological and Autonomic Effects

When pain is perceived, the sympathetic nervous system is activated, triggering a cascade of physical changes, including:
* Cardiovascular and Respiratory Changes: Heart rate and blood pressure typically increase, and respiration may quicken.12
* Hormonal Release: The endocrine system releases hormones such as epinephrine and norepinephrine, which help mobilize the body.1
* Metabolic Shifts: Blood glucose levels often rise to provide immediate energy, supported by the breakdown of liver glycogen.1
* General Excitatory Effects: Individuals may experience increased perspiration, tremors, and anxiety.1

Reflexes and Modulation

Beyond systemic changes, the body initiates local reflexes, such as the immediate withdrawal from a noxious stimulus. Internally, the body can modulate these signals through endorphins, which are natural pain-relieving chemicals that block pain reception in the spinal cord. In cases of chronic pain, the nervous system may undergo more lasting changes, such as increased excitability in spinal cord neurons or alterations in the thalamus and cerebral cortex.23