Pain Types, Assessment & Nervous System

• Pain can be acute, chronic, referred, or neuropathic, involving various nerve fibers and receptors
• Omega 3 fatty acids are often taken as NHPs for inflammation treatment and inhibit the arachidonic acid-conversion pathway

Acute Pain

• Acute pain is a normal physiological warning mechanism

Assessing Pain

• LATERSNAPS mnemonic aids in pain assessment: Location, Associated symptoms, Timing (onset, duration)
• Assess the Mechanism via asking how it started
• Severity can be rated on a scale of 0-10 or with faces tool for pediatrics
• Determine if there are Associated symptoms, such as fever
• Ascertain if the pain is Radiating or is 'referred pain'

Nervous System Communication

• The Central Nervous System (CNS) consists of the brain and spinal cord
• The Peripheral Nervous System (PNS) is the nerve tissue outside the CNS and ENS
• Sensory information travels within the afferent division
• Motor commands travel within the efferent division
• The Somatic Nervous System (SNS) and Autonomic Nervous System (ANS) coordinate motor and sensory information
• Special sensory receptors monitor smell, taste, vision, balance, and hearing
• Visceral sensory receptors monitor internal organs, while somatic sensory receptors monitor skeletal muscles, joints, and skin surface

Nerve Endings

• Different nerve endings are involved in sensing pressure, touch, temperature, and pain
• Pressure-sensitive endings include Pacinian corpuscles and Ruffini's endings
• Meissner's corpuscles and Merkel disks are used for fine touch
• Free nerve endings sense temperature and pain

Afferent Pathway

• Sensory information travels from the PNS to the CNS
• Sensory information starts at the sensory receptor in a specific body part
• Sensory information ends in the CNS's Somatosensory Cortex
• A sensory impulse must be strong enough to reach a threshold for action potential initiation

Nociceptors

• Nociceptors, 1st order neurons (PNS), are located in skin, bones, blood vessels, and visceral organs
• Nociceptors include A or C nerve fibers of the PNS, spinal nerve, dorsal root & ganglion, posterior horn synapse ('substance P' neurotransmitter)
• Signals ascend the spinal cord's white matter column via the 'spinothalamic tract' (lateral)
• Signals then travel to the thalamus ('relay station'), synapse with 3rd order neurons => somatosensory cortex in the brain

Sensory Homunculus

• The sensory homunculus corresponds to specific body parts, and creates awareness

Stimuli

• Large stimuli may trigger many or all receptors, leading to high awareness of pain
• Examples of large stimuli may be trauma such as tissue tearing, involving pressure receptors, free nerve endings and temperature changes in blood

Non-Pharmacological Techniques

• Decreasing inflammation & sensation (PNS): Ice
• Alleviate the trigger (PNS): Massage, Physiotherapy
• Distraction/behaviour modulation (CNS): CBT, Activities

Pain Terminology

• Visceral pain is deep pain, organ-related
• Cutaneous pain is superficial, surface-related
• Referred pain is due to body surface innervation by the same spinal nerve/nerve plexus + interneuron communication
• Reflexes: withdrawal reflex
• Chronic pain is persistent
• Neuropathic pain indicates persistent nerve irritation; difficult to treat
  • e.g. allodynia (pain caused by a non-painful stimulus)
  • e.g. hyperalgesia (hypersensitivity to a painful stimulus)
  • e.g. paresthesias ('pins & needles') and can occur with decreased perfusion of a nerve
• Phantom pain indicates neuropathic pain post amputation
  • It is caused by active spinal cord neurons and communicating interneurons despite lack of stimulus
  • Often leads to chronic pain

Dermatomes

• Dermatomes are cutaneous segments serviced by spinal nerves and are clinically useful for determining sensory/motor pathways

Reflexes

• Reflex: flexor 'withdrawal' reflex includes stimulus of sharp pain that causes reflex to withdraw without cerebral control
• There is activation of sensory neuron (afferent), interneuron (at level of stimulus in CNS)
• There is automatic activation of a motor neuron (efferent) - response by the effector and the awareness

Acute pain vs Chronic pain

• Acute pain lasts less than 10 days and is self-limiting
• Acute pain triggers endogenous modulators secretion and SNS responses
• Acute pain utilizes an innate protective mechanism and benefits from appropriate treatment
• Chronic pain lasts more than 6 months and travels along C fibres
• Chronic pain causes neurogenic inflammation
• Chronic pain is triggered by under-treated acute pain or chronic inflammatory disorders
• Chronic pain is not self-limiting, lacks endogenous modulators, and has inactive SNS responses
• It is a destructive mechanism and yields dysfunctions

Endogenous Neurotransmitter Modulators

• Endogenous opioid peptides: endorphins, enkephalins, dynorphins
• Serotonin & norepinephrine are released from the CNS, hypothalamus, limbic system, reticular formation
• DESCENDING (efferent) pathways bind opioid receptors to inhibit substance P
• Substance P is an excitatory CNS neurotransmitter which propagates pain input

Pain Gate Theory

• Pain Gate Theory suggests that pain signals are interrupted in the substantia gelitanosa of the spinal cord

Explore acute and chronic pain, assessment techniques using LATERSNAPS, and nervous system components like CNS and PNS. Understand pain mechanisms, severity scales, and the roles of sensory and motor divisions. Learn about referred pain and nerve communication pathways.