UNIT VII: PAIN

Objectives: By the end of this lecture the students will be able to: • Review the concept of somatosensory pathway.• Describe the function of Nociceptors in response to pain

information.• Describe the function of endogenous analgesic

mechanism as they relate to transmission of pain information.

• Describe the proposed mechanism of pain relief associated with the use of heat, cold & TENS i.e. Transcutaneous electrical nerve stimulation

Somatosensory Pathway

• Sensory pathways consist of the chain of neurons,

from receptor organ to cerebral cortex, that are

responsible for the perception of sensations.

Nociceptor

• A nociceptor is a sensory neuron that responds to potentially damaging stimuli by sending signals to the spinal cord and brain.

• This process called nociception, usually causes the perception of pain.

• It is the afferent activity. 

Pain • An unpleasant sensation associated with actual or potential tissue damage.• Pain is an unpleasant or emotional experience Pain is an unpleasant or emotional experience originating in real or potential damaged tissueoriginating in real or potential damaged tissue

• Unpleasant sensations (Sensory and emotional) associated with either potential or actual tissue damage.

Pain

Acute pain

• Acute pain is a protective mechanism that alerts the individual to a condition or experience that is immediately harmful to the body.

• Sudden onset, short duration, severe • It lasts less than 6 months • It often results from injury, surgery• It is presenting symptoms of some infections i.e.

pharyngitis, appendicitis, otitis media etc.

Chronic Pain • Continuous, long term processContinuous, long term process

• Lasts more than 6 months.Lasts more than 6 months.

• Examples: Back pain, cancer pain, arthritis Examples: Back pain, cancer pain, arthritis

Conti

Cutaneous pain Cutaneous pain • It is superficial coming from the skin or close to the It is superficial coming from the skin or close to the

surface of the body.surface of the body.• It is sharp pain It is sharp pain

Deep somatic pain • Deep somatic pain originates from deep structures Deep somatic pain originates from deep structures • i.e. muscles, joints, blood vessels etc.i.e. muscles, joints, blood vessels etc.

Conti

Visceral pain Visceral pain •Visceral pain refers to pain in internal organs, the Visceral pain refers to pain in internal organs, the abdomen, abdomen, oorr chest chest..•i.e. renal pain, peptic ulcer pain, pain in cholecystitis i.e. renal pain, peptic ulcer pain, pain in cholecystitis etcetc

Referred painReferred pain• Referred pain is pain that is present in an area distant Referred pain is pain that is present in an area distant from its point of origin. The area of referred pain is from its point of origin. The area of referred pain is supplied by the nerves from the same spinal segment supplied by the nerves from the same spinal segment as the actual site of pain . i.e. MI pain etc.as the actual site of pain . i.e. MI pain etc.

Naturopathic Pain • It is caused due to peripheral nerves damage .i.e.

Trigeminal neuralgia.

Neuralgia • It is characterized by severe, brief, often repetitive

attacks of throbbing pain.

Endogenous Analgesia System

Endogenous capability of the brain itself to suppress the input of

pain signals to the nervous system by activating a pain control system,

called an analgesia system.

Endorphin and enkephalin

• Endorphin and enkephalin are the body's natural painkillers. When a person is injured, pain impulses travel up the spinal cord to the brain.

• The brain then releases endorphins and enkephalins.

• Enkephalins block pain signals in the spinal cord.

• Endorphins are thought to block pain principally at the brain stem.

• TENS is the method of applying minute amounts

of electrical stimulation to a large diameter

nerve fibers via electrodes placed on the skin.

TENS (Transcutaneous electrical Nerve stimulation)

Cont…

• Presynaptic inhibition in the dorsal

horn of the spinal cord

• Endogenous pain control (via

endorphins, enkephalins) 

• Direct inhibition of an abnormally

excited nerve

• Restoration of afferent input

Cold therapy

• Cold slows down blood flow to an injury, thereby reducing pain and swelling. Cold therapy slows circulation, reducing inflammation, muscle spasm, and pain. It should be used if the area is swollen or bruised.

Heat therapy

• Heat opens up blood vessels, which increases blood flow and supplies oxygen and nutrients to reduce pain.

•  The warmth also decreases muscle spasms and can increase range of motion. 

References

• Porth, MC. (6th ED). Pathophysiology. (2002). Philadelphia. USA. Lippincott Willams& Willkins, A Wolters Kluwer Company

• McPhee, J. S., & Papadakis, A. M. (2011). Current Medical Diagnosis and Treatment. (50th ED). Chicago. USA: Mc Graw Hill