Day 2 lecture: Pain Flashcards
The spinothalamic tract also sends collaterals to ____ (3)
- Reticular formation 2. Hypothalamus 3. Other Limbic structures (emotions) (associated more with c fibers)
True or False: Area of referred pain is supplied by the SAME spinal segment as actual site of pain.
True
Where can you find the cell body of the first order neuron?
Dorsal Root ganglia
FYI: A primary order neuron is a nerve and is part of the PNS. 2nd and 3rd order neurons are NEVER part of the nerve. (CNS)
So, in the test, he will name some crazy nerve name and will ask what kind of neuron it is. Answer is: Primary order neuron.
What lamina is involved in both WDR and NS
Lamina 1,2,5
Name 7 chemicals released by tissues that stimulate nocireceptors. (Pain mediators)
Bradykinin Serotonin K ions Prostaglandin (PGE-2, PGI-2) Substance P Histamine ACh
Pain Pathway Propagation of impulses along spinothalamic pathway then relayed by thalamus to the primary sensory cortex.
Transmission
Layers within the dorsal horn.
Lamina
Which lamina do C-fibers synapse with the second order neurons?
Lamina 1,2
True or False: Opioid analgesic and stimulation produced analgesia are produced via the same descending inhibitory system.
TRUE
These (3) substances are thought to be involved in endogenous analgesic pathway.
Norepinephrine, serotonin, opioids
Type of Pain: Pain is experienced at a point distant to its point of origin.
Referred pain
PAG receives impulses from many brain regions including ____ (3).
- hypothalamus 2. Thalamus 3. Cortex
The gate control theory is based on ______ of pain information produced by mechanical stimulation, and provides the basic rationale for the TENS.
presynaptic inhibition
Conduction speed of C Fibers
0.5 - 2 meters /sec (Slow and second pain)
Transduction is accomplished by what neuron?
First order neuron
Axons from the rap he nuclei, locus coeruleus and VTA project to the spinal cord dorsal horn by way of the ____ to terminate in Lamina 1,2,4,7.
dorsal longitudinal fasciculus. (DLF)
Pain Pathway: Affective/ motivational aspect.
Perception
Nociceptors are terminal endings of ______.
primary afferent fibers.
Neurotransmitters released by A-delta and C fibers are ____ (3)
Calcitonin gene-related peptide Glutamate Substance P
Opioid peptides acts on the presynaptic terminals of nociceptor fibers to prevent the release of ____ (2)
Substance P and glutamate
Starting point of descending inhibitory pathway
PAG in the caudal midbrain (PAG –> NRM –> spinal cord level)
True or False: The axon terminus of Secondary Neuron contains opioid receptors.
true
Area stimulated to produce SPA (stimulation produced analgesia)
- PAG: Periaqueductal gray 2. NRM: Nucleus Raphe Magnus 3. CN: Caudate Nucleus 4. SN: Septal Nucleus
Type of nocireceptor: Responds to more than one type of stimulus.
Polymodal
What substance (Opiate antagonist) blocks the effects of endorphin/ enkephalins?
Naloxone
Pain receptors
Nociceptors (Noci = harmful)
2 theories on Modulation of Pain
- Gate Control theory 2. Endogenous analgesic pathway
Type of Pain: Pain result from direct injury to nerves in the PERIPHERAL NERVOUS SYSTEM.
Neuropathic pain.
Difference between A-Delta Fibers and C- fibers
refer to slide 8
It forms the spinothalamic tract.
axons from the large cells
3 Primary afferent fibers (1st order neurons)
A-Delta and C fibers: for pain A-Beta: for general sensation
What type of cells are found in Lamina II
Both inhibitory and excitatory cells
The electrical stimulation of PAG and NRM inhibits _______ in laminae ____ (3).
spinal thalamic cells (2nd order neurons)…. laminae 1,2,5
The route from the PAG to the spinal cord is not direct. It appears to involve a link with ____ (3).
- 5HT-rich rap he nuclei 2. Norepinephrine from locus coeruleus (LC) 3. Dopamine from the ventral tegmental area (VTA)
Nociceptors can be classes into (2) ___. They are the two pain primary afferent neurons
- Myelinated A-Delta 2. Unmyelinated C fibers
It will release inhibitory neurotransmitters that will hyperpolarize the axon terminals. Therefore makes it less able to release neurotransmitters into the synapse. It will make it harder for action potential to occur in the secondary neuron.
Inhibitory interneuron at Lamina 1.
These are collection of cell bodies in the PNS
Ganglia
What lamina is involved with Low threshold stimuli?
Lamina 3,4
Type of Pain: Sudden onset, temporary (disappears once stimulus is removed), may be associated with ANXIETY.
Acute pain
Type of Pain: Stimulation pof receptors in internal organs, abd and skeleton. It is often poorly localized; it can be referred pain.
Visceral pain.
This theory states that non-painful afferent impulses entering the cord inhibit painful input (ascending pathway). Touch receptors vs pain receptors.
Gate control theory
These interneurons can exert an inhibitory effect on synapses between primary and secondary neurons.
Interneurons in the substantia gelatinosa
Conduction speed of A-Delta fibers
5 - 35 meters /sec (Fast and first pain)
Two actions of PAG
- Activation of the descending pathway from NRM 2. Activation of ascending connections acting on higher subcortical levels of the CNS
Stimulation produced analgesia elicits release of ____ (3), which modulates pain transmission by inhibiting incoming sensory activity.
Endorphin and enkephalins Serotonin
Type of Pain: It is caused by stimulation of receptors in muscles, joints and tendons.
Deep Somatic Pain
The spinothalamic tract collateral pathway mediates arousal and emotional reactions. It is also responsible for _____.
somatic and autonomic motor reflexes.
This lamina is the most dorsal (“back”) and is a thin layer of large cells, together with small INHIBITORY INTERNEURONS.
Lamina 1
Type of Pain: It is a pain which there is no physical cause. It is not however imaginary pain and can be as intense as somatic pain.
Psychogenic
Type of Pain: Pain results from activation of pain receptors (nociceptors).
Nociceptive pains
Type of Pain: It is a pain originating from an actual physical cause e.g. tissue trauma, ischemia, etc…
Somatogenic
Perception of pain is dependent upon (5)
- Cellular damage 2. Conscious awareness of stimulation of pain 3. Ascending neural pathways 4. Receptor stimulation 5. Sensory cortex arousal
Enkephalins inhibit nociceptor release. Where is the site of enkenphalin release?
Dorsal horn interneuron synapses.
Type of nocireceptor: Responds to only one type of stimulus
Unimodal
Free nerve endings of sensory neurons found in all tissues and organs except ____.
the brain
Pain pathway: Transmission is modified.
Modulation
The modulation of pain by electrical brain stimulation results from the activation of descending inhibitory fibers, which modulate the input and output of laminae _____ (4) .
1,2,5,7
Primary fibers (A delta and C fibers) enter the spinal cord via the ____.
Dorsal root
This theory states that there are substances involved in brainstem descending inhibitory pathways that modulate pain in the spinal cord.
Endogenous analgesic pathway.
Both A-Delta and C fibers synpase in the ____.
Dorsal horn of the spinal cord.
True or False: A-Delta and C fibers have HIGH threshold for stimuli.
True
Receptors at the pre-synaptic terminals (2)
Mu and Kappa receptors.
Other name for Lamina 2
Substantia gelatinosa
The C fiber pain transmission goes through the _____ before reaching the thalamus.
Brain stem reticular formation
These are collection of synapses in the CNS
Nucleus (like thalamus, cortex)
In Gate Control Theory, it is thought that ______ stimulate endorphin releasing interneurons in dorsal horn, thereby closing the “gate”.
A Beta fibers
Dorsal horn is divided into how many layers (lamina)?
5 or 6
Chronic pain is persistent, usually lasting more than ___ months.
6 months
True or False: Knowledge of different types of referred pain is important in clinical diagnosis because in many visceral ailments the only clinical signs is referred pain.
True
The dorsal horn regulatory circuits involve ____ (3)
- primary afferents 2. spinal interneurons 3. descending fibers.
Pain Pathway: Noxious stimuli is translated into electrical activity at sensory nerve endings.
Transduction
Interneurons in the substantia gelationsa release opioid peptides, namely (3)
- enkephalins 2. Beta-endorphins 3. dynorphins
This is the intrinsic analgesia pathway.
Stimulation produced analgesia (SPA) or Behavioral analgesia
Other name for Lamina 1
marginal zone
It responds to noxious stimuli and convert energy at the site of the stimulus into neural impulses.
Nociceptor
3 types of stimuli
- Thermal: Heat or cold 2. Mechanical: tearing, crushing, stretching 3. Chemical: Inflammatory mediators, lactic acid, ischemia
This region is believed to control the “connectivity: of other laminae in the dorsal horn.
Lamina 2 (substantia gelatinosa)
An example of a mu opioid analgesic.
Morphine
When the threshold level of the stimulus is reached, then _____ occurs along these fibers in the form of action potentials.
depolarization
This means a decrease in the pain threshold.
hyperalgesia
What neuron is responsible for the propagation of impulses along the spinothalamic pathway?
2nd order neuron
Components of brainstem (3)
- Medulla 2. Pons 3. Midbrain
It has a role in analgesia and is rich in opioid receptors.
PAG in the midbrain
Examples of treatment modalities that supports gate control theory.
Acupuncture, TENS, psychogenic excitation of central analgesia system.
What type of neurons are found at the sensory pathway/ tracts?
2nd order neurons
Type of Pain: It is caused by stimulation of receptors in skin.
Superficial Somatic Pain
The psychological response of chronic pain may include ____.
DEPRESSION
What neuron is responsible for relaying the impulses by the thalamus to primary sensory cortex?
3rd order neuron
Pain inhibitory pathway can be activated by ____(3).
- Brain stimulation 2. Intracerebral microinjection of morphine 3. Peripheral nerve stimulation.
The main neuronal pathway activated by PAG stimulation extends first to ________ and then to _____.
NRM in the medulla …….. dorsal horn interneurons.
This laminae receive input from cutaneous A-Beta non-nociceptive afferents and contain cells with low-threshold receptive fields that respond to innocuous sensations.
Lamina 3,4,5,6
The primary neurons synapses with secondary neurons in the ____.
grey matter of the dorsal horn.
Receptor found in voltage dependent calcium channels.
Delta receptors
The dorsal root ganglia is found in the CNS or PNS?
PNS
Modulation of Pain by the action of opioids are achieved in two ways, namely:
- Inhibit neurotransmitter release by activation of K channels on pre-synpatic terminal (mu and kappa receptors). It hyperpolarizes cell 2. Inhibit neurotransmitter release by inhibiting voltage-dependent calcium channels (Delta receptors)
____, ____, _____ interact to create subjective emotional experience of pain (PERCEPTION).
transduction, transmission, modulation
In electrical stimulation, noxious information from nocireceptors are modulated at the _____.
spinal cord level
It is an unpleasant sensory or emotional experience associated with actual or potential tissue damage.
Pain (it is subjective)
These enhance receptor response to noxious stimuli.
Pain mediators
The modulation of pain involves which pathway? (Ascending or descending)
descending inhibitory pathway.
These are also known as the superficial dorsal horn.
Lamina 1 and 2
Which lamina do A-Delta fibers synapse with the second order neurons?
Lamina 1,2,5
Type of Pain Persistent, cause may be due to neural stimulate or decrease in endorphins.
Chronic Pain
In dorsal horn, interneurons in the _____ can regulate the conduction of ascending afferent input.
substantia gelatinosa (Lamina 2)
It has an important role in modulating pain transmission through spinal and supraspinal mechanisms.
Dorsal Horn
FYI: The secondary order neuron crosses to the other side of the cord. If it came in from the right dorsal root, it will end up ascending on the LEFT side of the cord.
;)
FYI: You can block neurotransmitter transmission by blocking calcium influx.
;)
