Sensory: pain and temp Flashcards
Nociception (sensing pain) can be subdivided into thermosensation, chemosensation and mechanosensation. What are the molecular differences? Give some examples for ion channels belonging to each of the three categories. Explain their membrane topology, channel subunit composition, ion selectivity and gating mechanism.
Thermosensation: gated temperature changes, TRPV1 (sensing capsaicin and > 42 C) - micromovements in any direction
Chemosensation: gated by a chemical ligand TRPM8 (sensing methol), GPCR
Mechanosensation: mechanically gated by either forces from lipids, or forces from filaments: SWELL1 (osmoregulation in vertebrates)
What structures are responsible for sensing pain and temperature?
Free nerve endings
Are the nocireceptors and thermonreceptors in the free nerve endings in the skin low treshold or high treshold receptors?
High treshold
Describe the general route in the PNS for afferent noci-, mechano and proprioceptors.
The primary afferent neuron go through the dorsal root ganglion (cell body) –> dorsal horn (Lissauer’s tract) innervating secondary afferent CNS neurons –> CNS neurons go through the spino-thalamic tract –> spine –> thalamus
What types of fibers are involved in nociception?
A-delta: thin myelin sheath neurons
C: thin, slow conducting fibers (longer lasting pain like headache), unmyelinated
What NT are the pain fibers using?
Glutamate + neuropeptides to amplify the signal
Where are capsaicin binding?
Intracellularly
What kinds of inputs does the 1st layer in the dorsal horn receive?
Sharp pain, burning pain, warmth, cold, itch and sensual touch
What kinds of inputs does the 5th layer in the dorsal horn receive?
Receive input from both touch and pain, wide dynamic range neurons
What pathway does the pain and temp sensing secondary fibers take in the spinal cord?
The anterolateral root
What pathway does the mechanosensory sensing secondary fibers take in the spinal cord?
The dorsal column root
Which side of the body will a lesion in the left side of the spinalcord effect on pain/temp and on mechanoception?
Pain/temp: the opposite side
Mechano: same side
Describe the central pathway of visceral pain.
–> dorsal root ganglion –> gracile nucleus in the medulla –> medial lemniscus pathway to the thalamus –> insular cortex
Describe the sensory-discriminative (1st pain) route.
Anterolateral system –> ventral posterior lateral nucleus in the thalamus –> somatosensory cortex (SI, SII)
Describe the affective-motivational (2nd pain) pathway.
Example: anterolateral system –> parabrachial nucleus –> hypothalamus –> amygdala –> anterior cingulate cortex and insula
