Other
Sensational Neuroscience
- Institution
- The University Of Nottingham (UON)
First-class notes summarising all the important aspects of sensational neuroscience to a high level of detail.
[Show more]
1 review
By: marie-rosecadeus • 1 year ago
Content preview
Sensational Neuroscience NotesLecture Series One
Lecture One: Introduction to Pain
Allodynia: - The perception of a painful stimulus in the absence of a painful stimulus.
• Or in the presence of an anxious stimulus e.g. a feather stroked across the skin.
This can activate mechanoreceptors in the skin. These then translate this
information in the form of a neural code. Representation A. There is processing of
an external stimulus by primary afferent neurons this is translated into a neural
code
• Noxious stimuli e.g. a fire, stimulus B is represented within the primary afferent
neurons with a different code. Representation B
• The brain needs to process the two different neural codes so that it can perceive
the two different types of pain
• Stimulus A’s neural code is sent to the first gate within the pain pathway. This
gate is represented within the spinal cord.
• So the primary afferent neurons in the skin send afferent projections to the dorsal
root of the spinal cord, the neural code is then transformed from A to a and now
the neural code is represented as ‘a’ in the spinal cord
• Primary neurons within the spinal code then send the new representation/neural
code to centres higher up in the thalamus
• Representation ‘a’ is then transformed into representation ‘α’
• The original stimulus, feather, has been changed a couple of times.
• ‘α’ representation is then sent to the somatosensory cortex, this then perceives
this stimulus as percept α
• Stimulus B activates a different cohort of primary afferent neurones
• This stimulus will activate nociceptive pathways
• Stimulus B is encoded within the primary afferent neurones as representation B
• A different subset of primary afferent neurones including c-fibres and noceptive
fibres transform the neural code from B to b
• This is sent to the thalamus
• Then it is transformed from b to β
• The thalamus then sends this information to the somatosensory cortex and is
perceived as percept β
• This allows the brain to perceive a noxious stimulus
1
,What happens in the spinal code when Representation A is not properly encoded by neurones within
the substantia gelatinosa within the dorsal horn of the spinal cord?
• This can cause maladaptive plasticity
• People with allodynia spinal cords translate representation A to representation A prime
• A prime looks more like representation B than representation A.
• The spinal cord will then send representation β to the thalamus
Neural Encoding
• There have been many theories about how peripheral afferent neurons that innervate the
skin encode both noxious and innocuous stimuli
• Intensity Theory: - Sufficiently strong activation of unspecialized neurons result in pain
- So it proposes that peripheral afferent neurones are largely
unspecialized and that if it is activated enough a painful stimulus will
occur but activating only a few results in an innocuous stimulus
- It is known now that this theory is incorrect as there is specialization
within the neurons
• Specificity Theory: - According to this theory high-threshold neurons respond to noxious
stimuli and it is their activation that causes pain
- AKA labelled line theory
• Combinatorial coding Theory: - According to this theory noxious stimuli activate high-
threshold
• Neurons and their activation are involved in evoking pain
- But the stimulus can also activate other PANs e.g. low-
Threshold neurons
- Because the central pathways carrying these signals interact,
Pain will depend on jointly on the HThN and LThN activation
Levels
- The nature of that joint dependence can take many forms
Diverse ways to produce pain
• A hot stimulus activates a primary afferent neuron
- The activation of nociceptors activates a second order neuron, within
the spinal cord causing the neuron in the spinothalamic tract to
synapse on a thalamocortical neuron
- This sends the information to the somatosensory cortex to the brain as
a painful stimulus
• When a cold stimulus activates primary afferent neurons
- The cold stimulus strongly activates cold responsive primary afferent
neurons
2
, - (2 is strong activation)
- It also activates another set subset of primary afferent neurons which
respond to cool temperature, Innocuous
- Both stimuli are processed within the spinal cord and activate the
respective second order neurons
- The second order neurons of the spinothalamic tract are synapsed
within the thalamus
- When the cold stimulus gets to the thalamus, the strongly activated
cold responsive neurons are inhibited by the cool responsive primary
afferent neurons
- So instead of getting a cold stimulus, there is only a modest activation
of the thalamic neurons
- However, because 2-1=1 there is still a cold painful stimulus in the
brain
• When there is an innocuous cold stimulus
- The cool stimulus can weakly activate cold responsive neurons
- It also activates cool responsive neurons
- These send their signals to the second order neurons
- These then project to the thalamus
- Because the neurons were only weakly activated, there is a
cancellation effect
- The cool responsive neurons inhibit the cold responsive neurons, then
there is no signal going to the brain
- It is not perceived as pain
3
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller akusika1. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £7.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
53022 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now