Noiceception

Exteroceptive, such as those that detect light, sound, odour, and tactile stimuli

Interoceptive, that detect events occurring in the interior of the organism.

Proprioceptive, exemplified by taste receptors, receptors in viscera;

Teleceptive (special) senses were excluded from above mentioned (vision, audition, olfaction, taste.

Teleception - special senses

Interoception - deep sensation

Exteroception - cutaneous sensation

Proprioception - visceral sensation

Nociception - pain sensation

Epicritic – determined accurately, precisely; said of cutaneous nerve fibers sensitive to fine variations of touch (related to senses conducted in dorsal columns).

Protopraxic – diffused, not precise, such as pain and sense of warm temperature (conducted through anterolateral system)

Epicritic – diffused, not precise, such as pain and sense of warm temperature (conducted through anterolateral system)

Protopraxic – determined accurately, precisely; said of cutaneous nerve fibers sensitive to fine variations of touch (related to senses conducted in dorsal columns).

Perception of proprioceptive stimuli from skin and internal organs, resultant from physical damages or diseases.

Perception of nociceptive stimuli from skin and internal organs, resultant from physical damages or diseases.

Pain is unpleasant sensory and emotional experience associated with actual and/or potential tissue damage or described in terms of such damage.

Sense of particular significance in biology of animals and humans, released as a warning signal.

Perception of teleceptive stimuli from skin and internal organs, resultant from physical damages or diseases.

Pain cannot be evoked without direct stimuli

Allodynia - Pain produced by stimuli which usually do
not elicit pain

Noxious stimuli present, but no pain felt.

Neuropathic pain - Pain initiated by primary lesion or
dysfunction

Pain isn't a sensory phenomenon

Pain is the product of complex, central, nociception- induced processing, and not a primitive sensation (IASP).

Pain isn't an emotional experience

Pain is a conscious, aversive aspect of somatic awareness,

Adaptation phenomenon is observed

Produces specific emotional state related to fear, it is NOT modified by previous experience.

Produces several responses and reflexes preventing or reducing the influence of harmful, nociceptive factor and effects of its action (withdrawal reflex)

Plays warning function, signaling real or potential damage.

Age - Younger people are more sensitive to pain

Gender - Males are more sensitive to pain

Age - Elder people are more sensitive to pain

Gender - Females are more sensitive to pain

Psychosocial factors

Fatigue – Humans often experience more pain when their body is stressed from lack of sleep.

Weather

Memory – How we have experienced pain in the past

Emotional status and type of personality,

Life experience

Functional status of entire PNS,

Acquired habits and education.

Is elevated by muscular contraction or work

Is lowered by nociceptive action in other regions of the organism.

Is elevated by conc. of one’s attention on non- nociceptive stimuli like touch, visual or auditory sensation.

Is lowered by muscular contraction or work,

Pain can be receptor dependant or independant

Fast pathway (12-30 m/s) built with myelinated Aδ- fibers responsible for „bright”, acute, sharp, easily localised pain – last short.

Slow pathway (12-30 m/s) built with myelinated Aδ- fibers responsible for „bright”, acute, sharp, easily localised pain – last short.

Fast pathway (0.5-2 m/s) built with unmyelinated C- fibers responsible for chronic, dull, intense, diffused, poorly localized and unpleasant filling – last long.

Nociceptive system - System identifies are of damage (or potential damage)

Antinociceptive system - System of sensing, transmitting, recognizing and localizing of the nociceptive stimulus.

Antinociceptive system - modulating sense of pain at level of post. horn of spinal cord (peripheral modulation)

Nociceptive system - modulating sense of pain at various levels of spinothalamic tracts, thalamic nuclei & thalamo-cortical linkages (central modulation)

The closer to the brain the stimulus is applied, the greater the temporal separation of two components.

In the spinothalamic tract there are A-delta fiber types

Anterior horn of spinal cord conveys sensation of simple touch

Lateral side of the spinal cord conveys fast and slow pain (pain and temperature)

Deep pain - is produced by chemical factors released in hypoxic muscles

Deep pain - is poorly localised, nauseating and associated with sweating and change in blood pressure.

Deep pain can be elicited from periosteum, ligaments, joints, fascias and blood vessels

Muscle pain is substernal pain in coronary disease and intermittent claudation

A beta fibers - free nerve endings

A-delta and C - paciniform corpuscles and ruffini terminals

Type 4 (unmyelinated) fibers - free nerve endings

Type 3 (A-delta, myelinated) fibers - free nerve endings and some specialised endings

Visceral pain - Observed in torn ligaments and sore muscles

Visceral pain -released by chemical, mechanical and osmotic stimuli.

Visceral pain - Pain is poorly localised, but doesn't radiate.

Visceral pain - poorly localised, nauseating, associated with sweating, changes in blood pressure (hypotension)

Visceral pain - deep somatic pain initiates reflex contraction of nearby skeletal muscles.

Visceral pain - goes through the ventral root ganglia to brain

Sensory neurons of the post. horn are not only converged by somatosensory protoneurons of skin sensation. They're converged by nociception originated from viscera.

Impulses conducted in visceral reflex arcs increase excitibility of neurons transmitting impulses from exteroceptors. They start to send nociceptive impulses

Divided into; Cervical, thoracic and lumbar

VRP areas of heart include left chest and left arm on medial side

VRP area of liver include right shoulder and clavicular area, as well as an area below the scapula

VRP of the stomach involves the lower back

No specialised receptor cells and they are slowly adapting receptors

Specialised receptor cells and they are slowly adapting receptors

No specialised receptor cells and they are rapidly adapting receptors

Free nerve endings sensitive to pain distributed in all the body organs (except for brain tissue and pulmonary parenchyma).

Unimodal receptors located on Aδ-fibers - Thermoreceptors responding to high temperature.

Polymodal receptors located on C-fibers - Naked nerve endings responding to mechanical stimuli

Silent nociceptors - Stimulated by temperatures > 42?C , low pH, capsaicin and other chemicals.

RPV1 receptors (capsaicin receptor) - Respond to nocicceptive stimuli only when inflammatory substances are present.

Hyperxemia (high O2 in tissues)

Physical trauma (mechanical, electrical or thermal damage)

Intrinsic chemicals (H+, K+, lactate, histamine, Ach, bradikinin, proteolytic enzymes, prostaglandins), capsaicin and extrinsic agents.

Inflammatory processes and neoplams

Facilitates pain - Bradykinin and leukotriens

Produces pain - Prostaglandins and cytokines (IL-1 & TNF-alpha)

Facilitates pain - SP and ATP

Produces pain - K+ and H+

Histamine is only facilitating pain, while serotonin only stimulates pain

Substance P (SP)

Neurokinin A (NKA)

Calcitonin gene related peptide (CGRP)

Dopamine

Glycine - suppresses the transmission of pain signals in the dorsal root ganglion.

Substance P - peptide (11 amino acids) released by C fibers; associated with intense, chronic persistent ("bad") pain.

Glutamate- suppresses the transmission of pain signals in the dorsal root ganglion.

Glycine - dominant neurotransmitter when the threshold to pain is first crossed; associated with acute ("good") pain.

Enter anterolateral system (lateral spinothalamic tract)

Enter anteromedial system (medial spinothalamic tract)

Enter posterolateral portion of the cord

Enter posteromedial portion of the cord

Ascend to specific sensory relay nuclei of thalamus, to areas S1, S2 and cingulate gyrus

Ascend to Hypothalamus

Ascend to Cerebellum

Ascend to reticular nuclei of brain stem, tectal area of mesencephalon and periaqueductal gray.

Ascend to the midline and intralaminar nonspecific nuclei of the thalamus and cortex

Spinal nerves - through VPM of thalamus to somatosensory cortex (3, 1, 2 Brodman’s area)

Trigeminal (cranial input) nerves - through VPL of thalamus to somatosensory cortex (3, 1, 2 Brodman’s area)

Trigeminal (cranial input) - nerves through VPM of thalamus to somatosensory cortex (3, 1, 2 Brodman’s area)

Spinal nerves - through VPL of thalamus to somatosensory cortex (3, 1, 2 Brodman’s area)

Lamina 1, 4 & 5 are origin of Lateral STT and Spinoreticulartract

Spino-reticular tract follows the somatotopic organisation

Lateral STT has bilateral body representation

Only Spinoreticular tract synapse in reticular formation

Spino-reticular tract has sub-cortical targets in autonomic centres, limbic system and hypothalamus

Lateral STT goes to VPL of the thalamic nuclei

Lateral STT has cortical location in parietal lobe (S1)

Spinoreticular tract goes to intralaminar and other midline nuclei of the thalamic nuclei

Spinoreticular tract has cortical location in parietal lobe (S1)

Role of Spinoreticular tract is dicriminative pain (quality, intensity & location)

Direct (fast) - Lateral STT

Direct (fast) - BIlateral

Indirect (slow) - Subcortical regions are Autonomic centres, limbic system, hypothalamus

Direct (fast) - perceives temperature and simple touch

Indirect (slow) - Thalamic nuclei is VPL

Afferent stimulation from sensory protoneurons reduces the pain in mechanism of presynaptic inhibition, preventing of excessive release of SP.

Efferent stimulation from sensory protoneurons reduces the pain in mechanism of presynaptic inhibition, preventing of excessive release of SP.

Afferent stimulation from antinociceptive centres in nucleus reticularis paragigantocellularis and nucleus raphe magnus.

Efferent stimulation from antinociceptive centres in nucleus reticularis paragigantocellularis and nucleus raphe magnus.

Antinociceptive system converging on dorsal horn are periaqueductal grey matter-nucleus raphe magnus - 5HT

Antinociceptive system converging on dorsal horn are Periaqueductal grey matter - ENK

Antinociceptive system converging on ventral horn are locus ceruleus - NE

Antinociceptive system converging on ventral horn are Periaqueductal grey matter - ENK

Met-enkephalin(Tyr-Gly-Gly-Phe-Met) is a natural ligand

Leu-enkephalin (Tyr-Gly-Gly-Phe-Leu) is NOT a natural ligand

There are two natural ligands

Opioids bind to receptors on interneurons of the pain pathways in the CNS

Enkephalins hyperpolarize the presynaptic membrane thus inhibiting it from transmitting these pain signals.

The enkephalin synapse with a dendrite or cell body.

Enkephalins are released at synapses of neurons involved in transmitting pain signals to the brain.

Enkephalins depolarise the presynaptic membrane thus inhibiting it from transmitting these pain signals.