What are the 4 major steps involved in the nociceptive pathway?
- Transduction
- Transmission
- Modulation
- Perception
Wha is transduction?
Transduction is the process of converting a mechanical, chemical, or thermal stimulus and turning it into an action potential
What is Transmission?
Projection of the action potential from the periphery through the dorsal horn propagating to the CNS
What is pain Modulation?
Pain modulation is the facilitation (amplify) or inhibition of action potential occuring at any point during the transmission process.
- Primary afferent nociceptor (PAN) releases Substance P (SP) and Glutamine (Glu) on synaptic cleft
- Stimulation of exitatory neurotransmitters and projection cells which amplify/ inhibit PAN signal
- Pain signal if strong enough continues to the brain.
What is pain perception?
The interpretation of the pain stimuli by the brain.
- Thalamus and sensory cortex: perceive, describe and localize pain
- Thalamus, brainstem (BS) and reticular formation: identiffy dull (long lasting), Diffuse pain
- Reticular formation and limbic system: control emotional and affective response to pain.
- Hypothalamus: conected to Cortex, BS, thalamus, perception of pain causes autonomic response
What is the aetiology of nociceptive pain?
The activation of primary afferent nerves with peripheral terminals that respond to noxious stimuli.
- Nocicepation may or may not be perceived as pain depending of interactions with nociceptive pathways
What are the types of tissue involved with nociception?
Somatic:
- skin
- muscle
- bone
Visceral
- Thoracoabdominal
- Pelvic organs
What is neuropathic pain?
- Unreleived noxious stimuli
- damage to nerve tissue
- etiology of neuropathic pain
What are the types of stimuli for nociceptive pain?
Pressure
temperature
chemical
In a nociceptive chemical stimuli what substances activate PAN?
Causes AP and secondary Hyperalgesia
- K+
- H+
- serotonin
- Bradykinin
- Histamine
In a nociceptive chemical stimuli what substances sensitize PAN?
Cause allodynia, primary hyperalgesia
- leukotines
- prostaglandins
- Substance P
In a neuropathic chemical stimuli, what substances activate PAN?
Cause Secondary hyperalgesia
- Norepinephrine
In a neuropathic chemical stimuli, what substances sensitize PAN?
Causes allodinya and primary hyperalgesia
- Prostaglandins
- Substance P
What substances Facilitate transduction?
- Prostaglandins
- Leukotines
- Histamine
- Seratonin
- Substance P
- Norepinephrine
What substances Inhibit transduction?
- NSAID
- steroids
- antihistamines
- capsacin
- anxiolytics
- non pharma theraphy
What are the pheripheal nerve fibres that transmit the action potential?
- ADelta fast highly myelinated
- C slow, no myelination
What are the 3 types of neurons in the dorsal horn?
Excitatory interneurons
inhibitory interneurons
projection cells
What is a possible expalnationn for refered pain?
Both visceral and nociceptive neurons decasate at lamina 2 in the dorsal horn, thus the body cant identify specifically where the pain signal is comming from and sends efferent neurons to the skin.
What are the pain inhibitors at the dorsal horn?
Chemicals
- GABA receptors
- calcitonin
- somatostanin
- Alpha 2
- NMDA receptor
Behaviour
- Massage
- Counterstrain
- TENS
Descending tracts
- Serotonin & norephinephrine (antidepresants)
- opoids
What are the pain facilitators at the dorsal horn?
chemical
- A delta and C fiber input
- Substance P
- NON- NMDA receptors
Where does the brain receive the signals from the ascending tracts (Spinothalamic)
- Cortex
- Thalamus
- Reticular activating system
What is the descending endogenous pain control mechanism?
- Periacueductal Gray (PAG)
- Opioids
What are the sensory pain elements in pain perception?`
Pattern
area
intensity
Nature of stimuli
What type of fibres enervate muscles
Afferent groups II, III, IV
WHat type of stimulus activates a joint
mechanical by stretching joint to end range
what type of stimulus activates a muscle
ischamia and pressure
what type of nociceptor fibres innervate the viscera
A-delta and C fibres
polymodal
respond to mechanical heat and chemical stimuli
How do silent nociceptors get activated?
fter tissue injury, they become activated and respond to noxious stimuli.
substances released as a result of the injury may sensitize the nociceptors, allowing them to fire to lower-intensity stimuli
What is neurogenic inflamation?
Neurogenic inflammation is a term used to describe the role of the nervous system in the development and maintenance of peripheral inflammation.
What are neuropeptides?
Neuropeptides such as substance P and calcitonin gene-related peptide (CGRP) are contained in small-diameter afferents (Groups III and IV).
