1) Pain is an unpleasant sensory and emotional experience caused by actual or potential tissue damage. It is the fifth vital sign due to its clinical significance. 2) Pain can be classified based on duration, location, intensity, and etiology. The general pain pathway involves nociceptors, spinal cord transmission to the brain, and response. 3) The spinothalamic tract involves first, second, and third order neurons transmitting nociceptive signals from receptors to the thalamus and cortex. The spino-reticular tract is also involved in emotional and behavioral responses to pain.

1. Mechanism of pain
Presented by;Sumaira
Roll no;29

2. Learning objectives
• Defination
• Pain as the 5th vital sign
• Signs and symptoms of pain
• Classification of pain
• General pathway (spinothalmic tract)
• Spino reticular tract

3. Define pain;
• An unpleasant sensory and emotional experience associated with
actual or potential tissue damage, or described in terms of such
damage.”

4. Pain as the fifth vital sign
• The American Pain SocietyCoined the phrase "Pain”The5th vital sign to emphasise
its significance and to Increase awareness among the health care professionals.
Documentation of pain assessment is now as prominent as the documentation of
traditional vital signs
• Highly subjective in nature
• Most common reason client seek medical advice
• Protective mechanism or warning to prevent further damage
• Most medical surgical problems are associated with pain, resulting either from;
• The disease process
• Treatment modalities
• Undergoing surgery
• Performed surgery

5. Signs and symptoms of pain
• Physiological manifestation
• Increased respiration,heart rate and bp
• Diaphoresis
• Dilated pupils
• Pallor
• Moaning
• Restlessness
• Irritability
• Facial expressions
• Verbal statements

6. Types of pain
• Pain can be classified in two major types
• 1.fast pain
• 2.slow pain
• Fast pain; is also described as sharp pain, pricking
pain,Acute pain, electric pain. it is elicited by mechanical and
thermal type of stimuli.
• Slow pain; is also called as
burning,aching,throbbing,chronic pain
• Elicited by thermal mechanical and chemical stimuli.

7. Based on duration
• Acute pain;
• Sudden onset
• Commonly associated with specific injury or damage
• Lasts from seconds to 6 months
• Temporary and disappears once stimulus is removed
• Can progress to chronic pain
• Chronic pain;
• Lasts longer then 6months
• Constant and recurring with mild to severe intensity
• Does not always have an identifiable cause
• Symptoms; fatigue,insomnia,anorexia, weight loss,anger

8. • Chronic non Cancer pain; eg:Low back pain, Osteoartitis,
headache etc.
• Chronic cancer pain;pain caused by Tumor progression
and related process, involves procedure , toxicities of
treatment& physical limitations.
• Chronic episodic pain; pain that occur sporadically over an
extended period of time
• Lasts for few hours,days or week
• E.g;Migräne headeach

9. Based on location
• Non referred pain;based on site at which pain is located eg;
headache,stomach pain etc
• Referred pain; is felt in areas other than irregular disease
part. It may occur when stimulation is not perceived in the
primary area e.g;pain of MI

10. Based on intensity

11. Based on Etiology
• 1.Nociceptive pain;when an intact properly functioning
nervous system sends signals that tissues are damaged and
requires care. Once stabilised pain goes away
• A) somatic pain;pain originated from skin,muscle,bone or
connective tissue e.g sharp cut,ankle sprain
• B)visceral pain;pain results from activation of nociceptors of
viscera (organs) like thoracic pelvic or abdominal viscera
• Pain can be cramping,throbbing, aching etc
• E.g;Angina pectoris

12. • 2.neuropathic pain; associated with damaged or
malfunctioning nerves due to illness injury or undetermined
reason
• using Chronic,burning,tingling,dull,aching and tends to be
difficult to trust
• A)peripheral NP; due to damage to PNS
• e.g; phantom limb pain
• B)central NP;damage to nerves in the CNS
• e.g; spinal cord injury pain

13. General pain pathway
(spinothalamic tract)
• Pain receptors (nociceptors);free nerve endings of first
order neuron (sensory neuron)
• present in skin,superficial tissues,muscles,bones, tendons,
ligaments,blood vessels,organs (except brain)
• A delta (myelinated); fast pain,well localised, sharp pain
(0.1sec)
• C (non-myelinated); Slow pain, poorly localised throbbing
and burning pain (after 0.1sec)

14. • Damaged tissue secrete;
• prostaglandins,histamin,cytokines,ATP,bradykini
n, serotonin ➡️stimulate nociceptors
• Noxious stimuli➡️stimulate sensory neurons ➡️
spinal cord ➡️brain (sense pain) ➡️through motor
neurons ➡️spinal cord ➡️to the body part for
reaction

15. 1st 2nd and 3rd order neurons
• 1st order neuron;from receptor to the spinal
cord(cell bodies are located in thedorsal root
ganglion)
• 2nd order neuron;from spinal cord to
thalamus
• 3rd order neuron; fromthalamus to sensory
cerebralcortex - terminate in thecerebral
cortex

16. Process of pain physiology
• Transduction;pain stimuli is converted to electrical signal. This
stimuli sends an impulse across a peripheral nerve fiver
(nociceptors) (first order neuron)
• Transmission; a delta fibers (myelinated) send sharp,localized &
distinct sensations ."(fibers unmylinated)relay impulses which are
poorly localised, burninh and persistent pain. First Order neuron
transmit informationVia neurotransmitter s to 2nd order neuron.
• Perception;person is aware of pain somatosensory cortex
indentifies the location and intensity of pain. Person unfolds a
complex reaction.
• Physiological and behavioural response is perceived (from
thalamus to somatosensory cortex)
• Modulation; inhibitory neurotransmitters like endogenous opioids
(endorphins and enkephalins via descending neurons

17. Spino reticular tract
• 2nd order neuron ascends to reticule formation of brain stem
➡️thalamus➡️hypothalamus ➡️cortex
• memory of pain,emotional and behavioural response to pain
• Face; 1st order neuron via trigerminal nerve in brain stem ➡️
2nd order neuron from thalamus ➡️somatosensory cortex
• From viscera;pain sensation from thoracic and abdominal
viscera ➡️sympathetic (thoracolumhar)nerves
• Eosophagus trachea and pharynx ➡️vagus and
glossipharyngeal nerves, pelvic region ➡️sacral
parasympathetic nerves

18. References
• https://youtu.be/GLAihrYlVdA
• https://youtu.be/MzTwWNqGcaY