Pilomotor reflex

Pilomotor Reflex

The Pilomotor reflex, also known as goosebumps or horripilation, is a physiological response that causes the hair follicles on the skin to stand erect. This reflex is controlled by the autonomic nervous system, specifically the sympathetic nervous system, and is often triggered by cold temperatures or emotional states such as fear, surprise, or arousal.

Mechanism

The pilomotor reflex is initiated by the hypothalamus, the part of the brain that regulates body temperature. When the body is exposed to cold temperatures or experiences strong emotions, the hypothalamus sends signals to the adrenal medulla, which releases adrenaline into the bloodstream. This adrenaline then binds to receptors on the arrector pili muscle, a small muscle located at the base of each hair follicle, causing it to contract and the hair to stand erect.

Function

The primary function of the pilomotor reflex is to generate heat and increase insulation by trapping a layer of air around the body. This is particularly useful in animals with a thick coat of fur, but less so in humans who have less body hair. In humans, the pilomotor reflex is more often associated with emotional responses. For example, it can occur during periods of intense emotion, such as fear or excitement, as part of the body's fight or flight response.

Clinical significance

Abnormalities in the pilomotor reflex can be indicative of certain medical conditions. For example, persistent or unexplained goosebumps can be a symptom of autonomic dysreflexia, a condition characterized by overactivity of the autonomic nervous system. Additionally, the pilomotor reflex is often absent in individuals with peripheral neuropathy, a condition that affects the peripheral nerves.

See also

• Thermoregulation
• Adrenaline
• Autonomic nervous system
• Fight or flight response

References

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