Neurophysiology of Nociception Flashcards
(35 cards)
Define pain according to the international association of pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage
What language did the word ‘nociception’ come from and what does it mean?
Latin word ‘nocere’ = to injure
What is nociception?
Mechanisms that provide notice of potential noxious substances or stimuli or injury
What is ganglion?
An encapsulated neural structure containing a collection of cell bodies of neurones
What is an afferent nerve?
A sensory nerve passing impulses from receptors to the central nervous system
What is an efferent nerve?
A motor nerve conveying information from the CNS to the muscles or glands
What is a nociceptor?
A receptor on a neurone (nerve fibre) which detect the actual or potential noxious stimuli
Pain in the orofacial region is transmitted mainly by the cranial nerve _, also known as the _______ ______. Exception angle of the jaw which is supplied by the ______ __________ _______.
V. Trigeminal nerve. Upper cervical nerves.
What are the three branches (+/- divisions) of the trigeminal nerve?
Ophthalmic (V1)
Maxillary (V2)
Mandibular (V3) + anterior (mainly motor exception long buccal) and posterior (mainly sensory exception nerve to mylohyloid) divisions
The _________ processes and relays sensory information to the varying parts of the brain. It plays a major role in ______ systems.
a) Thalamus, sensory
b) Thalamus, motor
c) Hypothalamus, sensory
d) Hypothalamus, motor
b) Thalamus, motor.
The _______ ______ is responsible for memory, language skills and consciousness. It governs voluntary motor control.
a) Pituitary gland
b) Medulla oblongata
c) Cerebral cortex
d) Spinal cord
c) Cerebral cortex
Algogenic substances are substances that are associated with signalling pain by activating or sensitising the nociceptors. What are the two algogenic substances that can be inhibited by analgesia?
a) Histamine, prostaglandins
b) Substance P, prostaglandins
c) Leukotrienes, prostaglandins
d) Bradykinin, prostaglandins
b) Substance P, prostaglandins
Nociceptive path:
1. Tissue damage
2. Release of _______ substances (via _________ on either an A-delta fibre or a C fibre in the trigeminal afferents)
3. Trigeminal (Gasserian) ganglion
4. Via the sensory root joining the __________ at the level of the pons
5. TNC in the brainstem: motor nuclei and sensory nuclei (mesencephalic, principal, spinal)
6. Thalamus
7. Interpreted by the brain and individual feels pain
8. Descending (motor) response
Algogenic
Nociceptors
Brainstem
Two types of nociceptive axons (fibres):
1) __-_______ (1st/fast) - fast, myelinated, respond to noxious high intensity mechanical stimuli
2) __-________ (2nd/slow) - slower, unmyelinated, respond to mechanical, thermal and chemical stimuli
A-delta
C-polymodal
Which statement is true:
1) There is very little cross-over within the trigeminal ganglion. Therefore the topography of the impulses (the relationship between the site that generated the impulse and the impulse) largely stays the same going into the brainstem
2) There is a lot of cross-over within the trigeminal ganglion. Therefore the topography of the impulses (the relationship between the site that generated the impulse and the impulse) largely varies going into the brainstem.
1) Very little cross-over within the trigeminal ganglion. Topography of the impulses largely stays the same going into the brainstem.
Within the brainstem, there is a sensory tract called the ________ ________ ________ (TNC). The primary afferents in the sensory root of the trigeminal nerve go into the sensory nuclei of the TNC which is composed of:
1. ___________ nucleus - responsible for proprioception from the periodontal ligaments and muscle fibres in the jaw close reflex
2. ___________ nucleus - responsible for proprioception for all orofacial behavious except for the jaw close reflex (eg kissing, smiling, talking)
3. ____________ (spinal tract or dosal nedullary horn) nucleus - receives the majority of the nociception from the primary afferents of the trigeminal nerve
Trigeminal Nucleus Caudalis
Mesencephalic
Principal
Spinal
Second order neurones take the information from the synapses, made with primary afferents in the ________ nuclei, up the brainstem, and feedback to the ________ nuclei as they ascend which can be used to help modulate pain.
a) Mesencephalic
b) Principal
c) Spinal
c) Spinal
Second order neurones travel to the __________ where they synapse with the third order neurones. These go to the higher centres in the brain which allow the individual to experience and interpret pain.
a) hypothalamus
b) thalamus
c) brainstem
d) cerebral cortex
b) thalamus
A ________ (motor) response is sent out by the brain once it has interpreted the signals presented to it from the periphery.
Descending
Other than altering stimulus or pharmacological alteration/interruption of nociception eg analgesia and anaesthesia, what are the two MAIN mechanisms of modulation?
- Descending impulses
- Sensitisation
Descending impulses mechanism of nociception modulation:
Descending impulses, which are endogenous chemical messenger eg endogenous ___________, from the brain via 1 route: ___________ ______ ________ (mid brain) -> __________ (Nucleus Raphe Magnus) -> ____________ ________, affect the transmission of impulses from primary afferents
Opioids
Periaqueductal gray matter
Medulla
Trigeminal nucleus
How descending impulses from the brain are generated is by gate control. This involves: as ____ signal becomes higher (very fast proprioception), it can inhibit the interpretation of the ______ or ____ fibre’s signals by the secondary neurones, therefore closing the gate, which brings further stimulus centrally.
a) Aβ, Aδ, C
b) Aδ, Aβ, C
a) Aβ, Aδ, C
What does hyperalgesia mean?
Increase in painful signal
What is allodynia?
Something that would normally not be interpreted as painful is very painful
