Lecture 20 Flashcards
Congenital Insensitivity to Pain
A condition that inhibits the ability to perceive physical pain
HSAN2
Is congenital (present at birth) or occurs very early on in life. There is universal absence of pain in most, and reduced ability to feel anything from touch (tactile sensation) in many, resulting in burns, mutilation of finger tips, painless fractures and painless arthritis with joint destruction
Limbic Touch
AKA ‘‘pleasant touch’’
-Associated with C-fibers
-Preserved in G.L.
Dorsal Horn of the Spinal Cord
1st Relay
2 Types of Spinal Projection Neurons
- Specific to Nociception
- Wide Dynamic Range
Specific to Nociception
Neuron only responds to noxious range
Wide Dynamic Range
Gradually increase its firing even in non-noxious range
Gate Control Theory
A mechanism, in the spinal cord, in which pain signals can be sent up to the brain to be processed to accentuate the possible perceived pain, or attenuate it at the spinal cord itself. The ‘gate’ is the mechanism where pain signals can be let through or restricted
-Inhibitory interneuron in substancia gelatinosa
-0 type of neuron
-rather pattern accross a region of neurons
Only C fibers are activated
-The T neuron is activated
-At baseline, the SG neuron always inhibit the T neuron
-But because it is inhibited by C fibers, it won’t inhibit the T neuron (inhibition removed = T activated 1+)
Only A fibers are activated
-The T transmission neuron is activated
-At baseline, the SG neuron always inhibits the T neuron
-But because the SG neuron is activated by A fibers, it increases the inhibition coming from the SG neuron (SG+)
C fibers than by tactile A fibers
In the Gate Control Theory, the T transmisson neuron is more activated by nociceptive…
Fibers C and A are activated at the same time
-C and A fibers are activate the T transmission neuron
-But the SG inhibitory interneuron is both activated and deactivated by A and C fibers. It remains ‘‘at baseline’’
-At baseline, the SG neuron always inhibits the T neuron
-The T transmission neuron does not benefit from the release of inhibition that takes place when only the C fibers are activated. Therefor, the T transmission neuron is less activated when the A and C fibers are activate at the same time vs. just the C fibers
-The T transmission neuron also does not benefit from extra inhibition that takes place when only A fibers are activated. Therefor, the T transmission neuron is more activated when the A and C fibers are active at the same time vs. just the A fibers
Transcutaneous Electrical Nerve Stimulation (TENS)
Uses low-voltage electrical currents to relieve pain
-Small device that delivers the current at or near your nerves to block or change your perception of pain
Opioids
They activate an area of nerve cells in the brain and body called opioid receptors that block pain signals between the brain and the body
Pre-synaptic Neuron
Activation of mu opioid receptors results in the entry of calcium into the synaptic terminal, which reduces the release of neurotransmitters into the synaptic cleft
Postsynaptic Neuron
Activation of mu opioid receptors results in the entry of potassium into the neuron, which hyperpolarizes the membrane and makes it more difficult to depolarize. As a result, the nociceptive signal is blocked in the spinal cord
Placebo Analgesia
Occurs when the administration of placebos leads to pain relief. Because placebos by definition lack active ingredients, the effect of this is considered to result from the patient’s belief that they are receiving an analgesic drug or other medical intervention
Naloxone
A medicine that rapidly reverses an opioid overdose. It is an opioid antagonist. This means that it attaches to opioid receptors and reverses and blocks the effects of other opioids
Referred Pain
When you have an injury in one area of your body but feel pain somewhere else. This happens because all the nerves in your body are part of a huge, connected network.
-Also enter spinal cord and coincide with information coming from skin
-Brain fooled that pain is coming from another place
-E.g. heart attack: patients feel pain spreading to arm
Brown-Séquard Syndrome
A rare neurological condition characterized by a lesion in the spinal cord which results in weakness or paralysis (loss of tactile discrimination, vibratory and proprioceptive sensations spastic paralysis) on one side of the body and a loss of sensation on the opposite side (loss of pain-temperature sensations) but remains on the opposite side
Descending Pain Modulation
-Not a 1-way phenomenon
-2 way road
-Brainstem important for modulating nociception in spinal cord
Conditioned Pain Modulation
Consist of the evaluation of a painful test stimulus followed by a second evaluation either at the same time as a distant, painful conditioning stimulus (parallel paradigm) or in series after the painful conditioning stimulus has been withdrawn (sequential paradigm)
-Descending controls activated by whole arm
Fibromyalgia
A chronic pain disorder characterized primarily by widespread musculoskeletal pain, accompanied by symptoms such as fatigue, cognitive disturbances (‘‘fibro fog’’), and sleep disruptions. The condition involves increased sensitivity to pain, odten described as widespread tenderness and heightened responsiveness of the nervous system. Although the precise cause remains unknown, this is thought to result from abnormal pain processing within the central nervous system
-When you look for injury –> none
-Pain in many body parts
Nociceptive Flexion Reflex (NFR)
AKA the withdrawal reflex, is an involuntary spinal reflex triggered by potentially harmful (nociceptive) stimuli, such as heat or mechanical pressure. It involves rapid contraction of flexor muscles to withdraw the affected limb from the source of pain, while simultaneously causing extension of muscles in the contralateral limb to maintain balance and stability (crossed-extension reflex). The NFR is widely used in pain research is an objective measure of spinal nociceptive processing and pain sensitivity
-Spinally mediated reflex
Effects of Emotions on Pain
Can cause physical symptoms, such as muscle tension or pain. When these symptoms are persistent, it may feel as though emotions are trapped in the body
-Unpleasant pictures cause a bigger reaction
-More of an effect
Spinal Modulation of Nociceptive by Music
-Stimulating + unpleasant music = higher arousal
