According to the International Association for the Study of Pain, pain is an unpleasant, subjective sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
Pain Theories
Specific Theory
1. Proposes that body’s neurons & pathways for pain transmission are specific, similar to other senses like taste
2. Free nerve endings in the skin act as pain receptors, accept input & transmit impulses along highly specific nerve fibers
3. Does not account for differences in pain perception or psychologic variables among individuals.
Pattern Theory
1. Identifies 2 major types of pain fibers; rapidly & slowly conducting
2. Stimulation of these fibers forms a pattern; impulses ascend to the brain to be interpreted as painful
3. Does not account for differences in pain perception or psychologic variables among individuals.
Gate Control Theory
1. Pain impulses can be modulated by a transmission blocking action within the CNS.
2. Large-diameter cutaneous pain fibers can be stimulated (e.g. rubbing or scratching an area) and may inhibit smaller diameter fibers to prevent transmission of the impulse (“close the gate”).
Current Developments in Pain Theory
Indicate that pain mechanisms & responses are far more complex than believed to be in the past.
Pain may modulate at different points in the nervous system.
First-order neurons at the tissue level
Second-order neurons in the spinal cord that process nociceptor information
Third-order tracts & pathways in the spinal cord & brain that relay/process this information
The role of the pain experience in the development of new nociceptors and/or reducing the threshold of current nociceptor is also being investigate
Types of Pain
Acute Pain
1. Usually temporary, sudden in onset, localized, lasts for 6 months; results from tissue injury associated with trauma, surgery, or inflammation.
Types of Acute Pain
· Somatic: arises from nerve receptors in the skin or close to body’s surface; may be sharp & well-localized or dull & diffuse; often accompanied by nausea & vomiting
· Visceral: arises from body’s organs; dull & poorly localized because of minimal noriceptors; accompanied by nausea & vomiting, hypotension & restlessness
· Referred pain: pain that is perceived in an area distant from the site of stimuli (e.g. pain in a shoulder following abdominal laparoscopic procedure).
2. Acute pain initiates the “fight-or-flight” response of the Autonomic Nervous System and is characterized by the following symptoms:
