PSYC30020 Lecture Notes - Lecture 17: Alpha Wave, Myelin, Aron Ralston
10 May 2018
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Lecture 17
- Pain definition: unpleasant sensory and emotional experience associated with actual
or potential tissue damage; lots of types/descriptions: aching, burning, throbbing,
electric shock like, dull, sore, nagging, piercing etc.; associated with crying,
sympathetic activation, behavioural changes
- Why have pain? → directs your attention to a danger and holds your attention
- Patients with congenital analgesia (cannot feel physical pain, 1 in a million, touch
receptors etc are unaffected) have reduced life span; such patients can bite off
significant proportions of their tongue while teething, develop bone infections in
undetected fractures, do dangerous things as kids because there is no reason why
not to
- Fixed factors influencing pain: genetics, age (older → more pain), sex (women →
more pain), hair colour (red heads have higher sensitivity to thermal pain, lower
sensitivity to chemical/electrical pain and need more anaesthetic)
- Modifiable factors influencing pain: context; prior life stressors/events; obesity;
anxiety/depression; attention; sleep
- Gate theory of pain: 1965
- There is a feedback loop in the spinal cord that determines which stimuli reach the
brain; chronic stress opens gate; adrenaline closes gate; explains how pain can be
ignored on battlefield but intensified when upset; rubbing sore limb/TENS may “close
gate”
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- Receptors:
- Nociceptors - sensory receptor capable of transducing noxious [unpleasant] stimuli;
free nerve ending; several classes which respond to different stimuli
- Stimuli - mechanical, temperature (extreme), electrical, chemical (Capsaicin [active
ingredient of chilli]: respond to heat/chilli/jalapenos)
- Inflammation (mechanical and increased nociceptor sensitivity)
- No pain receptors in brains and lungs
- A lot of pain receptors in skin, scalp etc
find more resources at oneclass.com
find more resources at oneclass.com
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- Pain nerves:
- Aδ fibres: some myelin, faster for sharp pain [myelin aids in faster signal
transmission]
- C fibres: no myelin, slower, dull aching pain.
- Synapse in the substantia gelatinosa in the dorsal horn of the spinal cord and use
glutamate (and substance P [ sensory function of substance P is thought to be
related to the transmission of pain information into the central nervous system]).
- Pain signal reach brain faster than touch signal because only two synapses between
parts of body and brain: one in spinal cord, one in medulla
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find more resources at oneclass.com
-
- Two sense pathways
- Pain signal crosses over contralateral side of spinal cord
- Touch sensation on ipsilateral side
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Pain definition: unpleasant sensory and emotional experience associated with actual or potential tissue damage; lots of types/descriptions: aching, burning, throbbing, electric shock like, dull, sore, nagging, piercing etc. ; associated with crying, sympathetic activation, behavioural changes. Directs your attention to a danger and holds your attention. Fixed factors influencing pain: genetics, age (older more pain), sex (women more pain), hair colour (red heads have higher sensitivity to thermal pain, lower sensitivity to chemical/electrical pain and need more anaesthetic) Modifiable factors influencing pain: context; prior life stressors/events; obesity; anxiety/depression; attention; sleep. Nociceptors - sensory receptor capable of transducing noxious [unpleasant] stimuli; free nerve ending; several classes which respond to different stimuli. Stimuli - mechanical, temperature (extreme), electrical, chemical (capsaicin [active ingredient of chilli]: respond to heat/chilli/jalapenos) No pain receptors in brains and lungs. A lot of pain receptors in skin, scalp etc. A fibres: some myelin, faster for sharp pain [myelin aids in faster signal transmission]
