Sensory Systems Flashcards
Explain how signal transduction of sensory information works
Sensory receptors transducer their stimulus into a depolarisation = generator potential
Generator potential evokes firing of action potentials for long distance transmission
Receptive field encodes location of stimulus
How is the intensity of the stimulus determined
Size of the generator potential (amplitude) and subsequent frequency of action potentials of encodes intensity
Where does sensory information terminate
Somatosensory cortex of the post central gyrus
What are the 2 types of pain
Sharp stabbing or diffuse throbbing
What fibres carry the fast (initial) pain
a-delta fibres
What fibres carry the slow (delayed) pain
C-fibres
What is referred pain
Pain felt in one part of body is actually caused by pain or injury in another
Nociceptors from different locations (e.g. chest, skin, heart) all converge onto the same second order neuron
E.g. injured pancreas could be causing pain in back
What is the route of the pain (nociceptive) pathway
Nociceptor fibres (a-delta and C-fibres) enter spinal cord via dorsal root
Once in dorsal horn the synapse onto their second order neuron
2nd order neuron decussates (crosses midlin) and projects up the spinothalamic tracts
What kind of drugs inhibit the nociceptive processing pathways
Analgesiacs
How does segmental control of nociceptive pathways work
Gate control theory: activity of receptive fibres (A-beta fibres) synapse onto inhibitory interneurons
These release inhibitory neurotransmitter (e.g. opioid) which inhibits release of neurotransmitter at synapse —> less transmission of nociceptive signals
How do Non-steroidal anti-inflammatory drugs (NSAIDs) work
Inhibit cycle-oxygenate which converts arachidonic acid to prostaglandins
Therefore less prostaglandins —> less sensation of bradykinin receptors —> fewer action potentials = less pain
How do descending pathways control pain
Also involves controlling the synapse
Cells in periaqueductal grey matter project down onto cells in raphe Magnus, these project down and synapse onto the inhibitory interneurons therefore inhibiting release of the nociceptor signals
