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Questions and Answers
What type of pain sensations do A delta fibres primarily transmit?
What type of pain sensations do A delta fibres primarily transmit?
- Deep, internal pain sensations
- Localized, sharp, and tingling pain sensations (correct)
- Episodic, emotional pain sensations
- Dull, generalized throbbing pain sensations
Which neuron type first transmits pain signals from peripheral areas to the spinal cord?
Which neuron type first transmits pain signals from peripheral areas to the spinal cord?
- Third order neuron
- Second order neuron
- Peripheral neuron (first order) (correct)
- Inhibitory interneuron
How do A beta fibres modulate pain signals from C fibres?
How do A beta fibres modulate pain signals from C fibres?
- By directly increasing the activity of C fibres
- By transmitting action potentials more slowly than C fibres
- By inhibiting the second projection neuron via action potential transmission (correct)
- By synapsing with the third order neuron directly
What role does the inhibitory interneuron play in pain transmission?
What role does the inhibitory interneuron play in pain transmission?
Which fibres are primarily responsible for transmitting sharp pain signals?
Which fibres are primarily responsible for transmitting sharp pain signals?
Flashcards
A delta fibres
A delta fibres
Myelinated nerve fibres transmitting sharp, localized pain sensations.
C fibres
C fibres
Unmyelinated fibres transmitting dull, throbbing pain sensations.
Three order neuron pathway
Three order neuron pathway
Pathway involving peripheral neuron, spinal projection neuron, and thalamic neuron for pain transmission.
A beta fibres
A beta fibres
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Inhibitory interneuron
Inhibitory interneuron
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Study Notes
Gate Control Theory of Pain Modulation
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Stimuli: Mechanical (sharp objects), thermal (extreme heat/cold), and chemical (tissue damage) stimuli trigger pain signals.
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Pain Fibers:
- A delta fibers: Myelinated, transmit sharp, localized pain sensations.
- C fibers: Unmyelinated, transmit dull, throbbing, generalized pain sensations.
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Pain Signal Transmission: Pain signals travel via a three-neuron pathway:
- First-order neuron: Peripheral, synapses with a second-order neuron in the spinal cord.
- Second-order neuron: Within the spinal cord, projects to a third-order neuron in the thalamus.
- Third-order neuron: In the thalamus, projects to the primary somatosensory area of the cortex for perception.
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Modulation by A beta fibers:
- A beta fibers: Myelinated fibers that carry touch sensations from mechanoreceptors.
- Faster Transmission: Myelinated fibers transmit action potentials (APs) faster than unmyelinated fibers.
- Inhibitory Interneuron: In the spinal cord, an inhibitory interneuron forms a synapse with the second-order neuron.
- Pain Inhibition: When A beta fibers are stimulated (e.g., by touching or rubbing an injured area), their faster APs reach the inhibitory interneuron before C fiber APs. This inhibits the second-order neuron, reducing the transmission of pain signals, thus reducing rather than stopping pain. This mechanism explains why applying pressure can alleviate pain.
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