Overview
This lecture covers the biological purpose of pain, types of pain, mechanisms of pain perception, referred and phantom pain, factors affecting pain experience, and pain management strategies.
The Purpose and Mechanisms of Pain
- Pain alerts the body to potential or actual tissue damage, providing protective function.
- Pain receptors (nociceptors) are free nerve endings found in skin and internal tissues, but not in brain tissue.
- Pain is triggered by temperature, mechanical forces, and chemicals.
- Adaptation to pain is minimal to ensure continued awareness of injury.
Visceral and Referred Pain
- Visceral pain receptors in organs sense stretch, chemicals, or ischemia but can't localize pain precisely.
- Referred pain occurs when pain is felt in a location different from its source, due to shared nerve pathways (e.g., heart attack pain felt in the left arm).
Types of Pain: Acute vs. Chronic
- Acute pain is sharp, fast, and well-localized, conducted by myelinated neurons.
- Chronic pain is dull, slow, and hard to localize, conducted by unmyelinated neurons.
- Chronic pain resists relief and can severely impact quality of life.
Factors Affecting the Pain Experience
- Individual pain tolerance varies due to receptor density, past experience, physiology, and culture.
- Women generally have higher pain tolerance due to childbirth.
- Cultural expectations influence pain expression (e.g., "real men don't cry").
Phantom Pain
- Phantom pain occurs after limb amputation due to nerve trauma, causing sensation in the missing limb.
Pain Modulation and Management
- Body releases natural painkillers: endorphins and enkephalins (neurotransmitters that block pain).
- Serotonin enhances release of natural painkillers and is linked to positive mood.
- Pain management methods include analgesics (Tylenol, Advil), physical therapy, massage, heat/ice, liniments, acupuncture, opioids, antihistamines, electric stimulation, nerve blocks, and antidepressants.
Key Terms & Definitions
- Nociceptor — nerve ending that detects pain.
- Visceral pain — pain originating from internal organs.
- Referred pain — pain perceived at a location other than the site of origin.
- Acute pain — sharp, fast, localized pain.
- Chronic pain — slow, dull, diffuse pain.
- Endorphins/Enkephalins — neurotransmitters that naturally inhibit pain.
- Phantom pain — sensation of pain in an amputated limb.
Action Items / Next Steps
- Review and highlight definitions of key terms, especially referred pain.
- Read the next lecture section or slide on pain pathways if provided.
- Study diagrams on referred pain locations for different organs.