Pain And Temperature - 20 Flashcards
(21 cards)
Define nociception
It is the activation of specialized sensory receptors that provide information about damaged tissue
Define pain
It is the perception of an aversive or unpleasant sensation from a specific region of the body can be categorized as fast or slow
List the four types of nociceptors
Thermal, mechanical, chemical, polymodal
Which nociceptors are thinly myelinated Adelta with rapid conduction speed?
Thermal and mechanical
Describe what thermal nociceptors respond to.
Extreme temperatures of > 45°C or < 5°C
Describe what mechanical nociceptors respond to.
Extreme or intense pressure
Which types of fibers make up polymodal nociceptors?
small diameter unmyelinated C fibers that conduct the signal very slowly (<1m/s)
What do chemical nociceptors respond to?
Chemicals released by damaged cells
What do polymodal nociceptors respond to?
High intensity stimuli of one or more of a variety of thermal, mechanical, or chemical
What descriptors are used for fast pain, from where in the body? And how quickly is it perceived?
Described as being sharp acute or electric associated with sensations in the skin. Perception of this pain occurs quickly within .1 seconds of stimulus onset.
Which receptors are associated with fast pain?
Thermal and mechanical receptors, Adelta
What descriptors are used for slow pain, from where in the body? And how quickly is it perceived?
Slow pain is described as being throbbing or burning and is associated with sensations that occur in deep tissues like organs but also sometimes with skin. Perception of this pain occurs slowly, within one second of stimulus onset.
Which receptors are associated with slow pain?
Polymodal nociceptors, Unmyelinated C fibers
How do nociceptors differ from other receptors? Hint adaptation
Nociceptors, unlike other receptors, are non-adapting. They will continue to fire at the same rate in the presence of a steady continuous stimulus. Some nociceptors actually increase their firing rate to a constant stimulus, this is called hyperalgesia.
Which fibers carry which temperature nociceptors?
Type C fibers carry warm and type Adelta fibers carry cold
Where do the DRG axons for temperature nociception synapse? Then where do these in turn synapse? And where do they ascend?
DRG afferent axons synapse on interneurons in laminae 1, 2 and 3, which in turn synapse on second order neurons in 5. Then the second order neurons ascend in the ALS
Which pain pathways for fast pain? And which fiber
Lateral spinothalamic with A Delta fibers
Explain the fast pain pathway for the body/extremities
DRG axons enter the dorsal horn and ascend 2-3 levels in Lissauer’s tract then synapse on second order neurons in one and five which are nociceptive specific and wide dynamic range neurons. The second order axons then cross the midline in the anterior white commissure and ascend in the ALS to the VPL in thalamus then project to the pain areas of the cortex.
Explain the fast pain pathway for the face
The CN V (Trigeminal) DRG enters the dorsal column in the pons and descends to the trigeminal nucleus in the medulla. The axon then decussates and becomes the trigeminothalamic tract and ascends to the thalamus VPM The axons from the neuron there projects to the face part of the homunculus in the somatosensory cortex.
What happens after a complete transection of the ALS?
Severe loss of pain and temperature sensation contralaterally
What happens with a partial lesion to the ALS?
Can result in severe pain sensation. Central pain syndrome or thalamic syndrome which causes spontaneous burning pain. Dysesthesia