Understanding and Managing Pain

Insensitivity to pain = many injuries

Somatosensory System

• Moves info. From body to brain

Neurons

• Afferent (sensory) neurons

• Interneurons - Connect sensory neurons to motor neurons

• Efferent (motor) neurons

Somatosensory cortex

Brain Scans

• PET

• fMRI

Pain

Definition of pain

• Sensation + emotional reaction to sensation

Types of pain• Acute

– Occurs when injured - cut, burn, childbirth, surgery– Adaptive– Warns of further injury

• Chronic– Lasts months or years– Not adaptive– No biological benefit– Reinforced by environmental factors

• Sympathy

– It is still real pain

The experience of pain

• Anzio beachhead– Carrying severed arm– People not realizing they were shot

Expression of pain

• Cultural background & social context – E.g. Childbirth– Rites of

passage

Theories of pain

Specificity theory of pain• Pain = amount of tissue damaged

– Pain largely uninfluenced by psychological forces

• Problems– No specific skin receptors devoted to relaying pain– Phantom limb pain– Injury without pain

• E.g. in war

Gate control theory of pain

• Sensory input is not the only factor in pain perception– Changes in the spinal column and brain

control the flow of neural impulses– Parts of spinal column can either

• increase (open the gate) or • decrease (close the gate)

Measurement of pain• 1. Self-report

– Rating scales (e.g. 0-10)– MMPI

• 2. Behavioral assessments– Observing a patient’s behavior

• 3. Physiological measures– Electromyography (EMG)

• Muscle tension• Not a very good method (Poor validity)

Phantom limb pain

• Common following amputation

• Decreases with time

Managing pain with medicine

• Self-paced administration of narcotics– E.g. morphine pump

• Limits are programmed in

– Avoids undermedication– Patients use less medication– Higher satisfaction

Managing pain with behavior

• Relaxation training– Reduces

• Headaches• Rheumatoid arthritis• Low back pain

• Behavior modification– Based on operant conditioning– Positive reinforcers for pain - e.g. sympathy

• Increase pain

– Reinforcing desirable (non pain) behavior• Reduces pain

Managing pain with behavior

• Cognitive behavioral therapy (CBT)– Changing your thinking patterns– E.g. “Reframing” - “Pain is weakness

leaving the body” - Used in the military