Central Nervous System and Pain Control
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Questions and Answers

Which structure in the central nervous system is primarily responsible for the secretion of endorphins during stress?

  • Hypothalamus (correct)
  • Raphe magnus nucleus
  • Dorsal horn
  • Preambulation gray matter

    • What is the role of enkephalin in the pain inhibitory complex?

  • To produce pain sensations
  • To block calcium channels in sensory afferent fibers (correct)
  • To increase the transmission of pain impulses
  • To stimulate the release of serotonin

    • Which of the following opioid peptides is secreted by the raphe magnus nucleus?

  • Serotonin (correct)
  • Enkephalin
  • Dynorphin
  • Endorphin

    • What type of pain do Aδ fibers primarily carry?

    <p>Fast, acute pain (B)</p> Signup and view all the answers

    Which system in the CNS is involved in controlling pain at higher levels?

    <p>Limbic system and hypothalamus (A)</p> Signup and view all the answers

    Where is the pain inhibitory complex located in the spinal cord?

    <p>Dorsal horn (A)</p> Signup and view all the answers

    Which type of therapy would likely involve the activation of the analgesia system through emotional stimuli?

    <p>Stress management techniques (B)</p> Signup and view all the answers

    The presence of which receptors is crucial in the pain control mechanisms discussed?

    <p>Opiate receptors (A)</p> Signup and view all the answers

    Which sensory modalities are typically lost in Syringomyelia due to damage to the lateral spinothalamic tracts?

    <p>Pain and temperature (D)</p> Signup and view all the answers

    What is a characteristic gait associated with sensory ataxia due to Tabes Dorsalis?

    <p>Broad base and looking at feet (A)</p> Signup and view all the answers

    In Tabes Dorsalis, which sensory tracts primarily degenerate, leading to loss of fine touch and vibration sense?

    <p>Gracile and Cuneate tracts (D)</p> Signup and view all the answers

    What symptom is associated with loss of proprioceptive sensations in Tabes Dorsalis?

    <p>Sensory ataxia (C)</p> Signup and view all the answers

    Which reflexes are preserved in the early stages of Tabes Dorsalis before significant damage occurs?

    <p>Visceral reflexes (D)</p> Signup and view all the answers

    What pattern of sensory loss characterizes a Syringomyelia lesion located in the lower cervical and upper thoracic segments?

    <p>Jacket distribution loss of pain and temperature (A)</p> Signup and view all the answers

    Which type of fiber is primarily responsible for slow pain perception and remains intact for long periods in Tabes Dorsalis?

    <p>C fibers (A)</p> Signup and view all the answers

    Which of the following is NOT a manifestation of Syringomyelia?

    <p>Increased muscle tone (A)</p> Signup and view all the answers

    What is the main mechanism involved in primary hyperalgesia?

    <p>Sensitization of pain receptors by pain-producing substances (D)</p> Signup and view all the answers

    In the context of pain transmission, what role do A beta fibers play?

    <p>They induce presynaptic inhibition at the spinal cord level (B)</p> Signup and view all the answers

    What is the defining feature of secondary hyperalgesia?

    <p>Pain sensation is prolonged and severe in uninjured areas (B)</p> Signup and view all the answers

    Which of the following accurately describes syringomyelia?

    <p>A slowly progressive disease that chiefly affects middle-aged females (A)</p> Signup and view all the answers

    Which substance is NOT involved in the sensitization of pain receptors in primary hyperalgesia?

    <p>Acetylcholine (B)</p> Signup and view all the answers

    What is a primary mechanism through which A delta fibers inhibit pain transmission?

    <p>Through presynaptic inhibition at small interneurons (B)</p> Signup and view all the answers

    Which statement about cutaneous hyperalgesia is true?

    <p>Pain sensations can be exaggerated due to non-noxious stimuli (B)</p> Signup and view all the answers

    How do impulses from areas of primary and secondary hyperalgesia interact in the spinal cord?

    <p>They converge on the same spinal gate resulting in facilitation (A)</p> Signup and view all the answers

    Flashcards

    Spinothalamic Tract Damage

    Damage to the spinothalamic tracts results in loss of pain, temperature, and crude touch sensation on the affected side of the body.

    Dorsal Column Damage

    Damage to the dorsal columns affects sensations like fine touch, vibration, and proprioception (sense of body position).

    Sensory Ataxia

    A condition characterized by uncoordinated movements due to loss of proprioceptive sensation (body position sense).

    Tabes Dorsalis

    A nervous disease caused by syphilis that gradually compresses dorsal roots, leading to sensory loss.

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    Romberg's Sign

    Positive Romberg's sign indicates a tendency to fall when eyes are closed, a symptom of sensory ataxia.

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    Gracile and Cuneate Tracts

    Tracts in the dorsal column that carry information about fine touch, vibration, and proprioception (sense of body position).

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    Pain and Temperature Loss

    Loss of pain and temperature sensation occurs due to damage of the lateral spinothalamic tract, usually at the lower cervical and upper thoracic segments.

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    Sensory Loss in Tabes Dorsalis

    Early sensory loss in Tabes Dorsalis primarily affects light touch, vibration, and position sense due to damage of the dorsal columns, while pain and temperature loss are typically later symptoms.

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    Spinal Gate Control

    A mechanism in the spinal cord that modulates pain signals. It involves the inhibition of pain signals by other neural pathways.

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    Primary Hyperalgesia

    Pain exaggerated in the area of an injury (including the surrounding area). Pain is produced by non-noxious stimuli.

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    Secondary Hyperalgesia

    Pain exaggerated outside the injured area and occurring longer. Painful reaction outside of the damaged tissue area. It is facilitated by pain impulses from the primary site.

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    Beta Fibers

    Afferent nerve fibers responsible for carrying sensory information other than sharp/pricking pain. They close the spinal gate affecting pain transmission.

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    Delta Fibers

    Afferent nerve fibers that carry sensations of sharp/pricking pain. They transmit impulses to the spinal gate for inhibition.

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    Presynaptic Inhibition

    A method by which pain signals are reduced in the spinal cord. The strength of a signal coming into a neuron is reduced by acting on the synapse before the nerve impulse reaches the next neuron.

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    Pain Threshold

    The point at which a stimulus is perceived as painful.

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    Syringomyelia

    A progressive neurological disorder affecting the spinal cord, often congenital.

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    Stress Analgesia

    The body's ability to suppress pain during extreme stress, like in battle, due to the release of endorphins.

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    Hypothalamus Role in Pain Control

    The hypothalamus releases endorphins in response to severe stress and emotional stimuli, activating the pain control system.

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    Prequeductal Gray Matter (PAG)

    A region in the midbrain that contains opioid receptors and releases enkephalin, a pain-suppressing neurotransmitter.

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    Raphe Magnus Nucleus

    A nucleus in the brainstem releasing serotonin, which stimulates the pain inhibitory complex to block pain transmission.

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    Pain Inhibitory Complex (PIC)

    A group of inhibitory neurons in the spinal cord's dorsal horn that block pain signals by releasing enkephalin.

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    Enkephalin's Role

    Enkephalin, a neurotransmitter released in the PAG and PIC, blocks calcium channels in sensory nerve fibers, preventing pain signals from transmission.

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    Pain Control System Locations

    The pain control system operates at different levels of the CNS, including the hypothalamus, preaqueductal gray matter, raphe magnus nucleus, and the pain inhibitory complex in the spinal cord.

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    Study Notes

    Central Nervous System

    • The central nervous system (CNS) is the complex network responsible for controlling the body's functions.

    Pain Control (Analgesia) System

    • Pain reactions vary significantly between individuals.
    • This difference is partially due to the brain's ability to suppress pain impulses via a pain control or analgesia system.
    • This system includes pain control at both higher central levels and spinal cord levels.

    Pain Control at Higher Central Level

    • The CNS has different levels where pain suppression occurs.
    • Each level contains opiate receptors, secreting opioid peptides (morphine-like action).
    • This mechanism, known as stress analgesia, helps soldiers endure battle pain until afterwards.
    • The hypothalamus and limbic system, reacting to severe stress and emotional stimuli, secrete the opioid peptide endorphin.
    • The preaqueductal gray matter, located in the midbrain and upper pons, contains opioid receptors stimulated by endorphin from the hypothalamus.
    • This structure also secretes the opioid peptide enkephalin.
    • The raphe magnus nucleus, situated in the lower pons and upper medulla, has opioid receptors stimulated by enkephalin from the preaqueductal gray matter.
    • It also secretes the opioid peptide serotonin.

    Pain Inhibitory Complex (PIC)

    • The PIC exists within the dorsal horn of the spinal cord.

    • It's a network of small inhibitory interneurons connecting with afferent Aδ fibers (fast pain) and C fibers (slow pain).

    • Opioid receptors within the PIC are stimulated by serotonin from the raphe magnus nucleus.

    • The PIC secretes enkephalin, which blocks calcium channels in afferent sensory fibers.

    • This presynaptic inhibition prevents pain-producing substances from being released from sensory afferents.

    • The PIC blocks pain impulse transmission at the initial entry point in the dorsal horn of the spinal cord (spinal gate).

    • Enkephalin prevents pain-producing substances from being released.

    • The PIC blocks pain impulses at the initial entry point in the dorsal horn of the spinal cord (spinal gate).

    Pain Control at Spinal Cord Level

    • Aβ fibers of the gracile and cuneate tracts, sending collaterals to inhibitory neurons in the PIC, lead to stimulation that inhibits and closes the spinal gate and obstructs pain transmission. This is demonstrated by the relief of pain when rubbing skin surrounding the painful area.
    • Aδ fibers, carrying pricking pain, also send collaterals to inhibitory interneurons within the PIC, triggering presynaptic inhibition and blocking pain transmission. This is a mechanism behind the pain relief offered by acupuncture and counterirritant treatments.

    Some Clinical Abnormalities of Somatic Sensations

    • Cutaneous hyperalgesia is a pathological condition where pain sensation from the skin is abnormally exaggerated.
      • Primary hyperalgesia: A pathological skin condition where pain arises from a non-noxious stimulus. This affects the area of the injury and the surrounding area of redness. Its mechanism involves pain receptor sensitization due to substances like histamine, substance P, and prostaglandins.
      • Secondary hyperalgesia: A pathological condition of the skin where a noxious stimulus causes prolonged and exaggerated pain, exceeding normal levels. This occurs in the healthy skin area around primary hyperalgesia. Pain threshold may be normal or elevated; however, the pain sensation extends and persists. It results from a convergence of impulses stemming from primary hyperalgesia areas merging and being enhanced at the same sensory gate.

    Syringomyelia

    • Syringomyelia is a progressive, congenital disease, typically affecting middle-aged females.
    • It's characterized by a cavity forming in the spinal cord's gray matter surrounding the central canal, leading to pressure and disruption of spinothalamic sensation (pain, temperature, crude touch) on both sides of the body.
    • Lesions are usually found in the lower cervical and upper thoracic segments.
    • Manifestations:
      • Loss of pain and temperature from affected segments.
      • Sensation transmitted through the dorsal columns (e.g., fine touch, vibration, proprioception) is unaffected since these tracts do not cross.
      • Crude touch is decreased but not lost, because some information is carried by dorsal column tracts.

    Tabes Dorsalis

    • This nervous condition is caused by syphilis.

    • It causes gradual compression of dorsal roots and dorsal root ganglia, leading to degeneration of the gracile and cuneate tracts.

    • The thoracic and lumbosacral regions are most commonly affected.

    • Manifestations

      • Severe pain attacks due to irritation of pain afferent fibers.
      • Loss of fine touch, proprioception, and vibration sensations, stemming from damage to the gracile and cuneate tracts (thick Aβ fibers are susceptible to compression). Loss of proprioception leads to sensory ataxia.

    • Sensory ataxia involves uncoordinated voluntary movement caused by a loss of position and movement sensations. Symptoms include positive Romberg's sign (falling when eyes are closed), a stamping gait, and looking at feet while walking.

    • The late manifestations include

      • Loss of pain and temperature in affected areas
      • Slow, persisting pain
      • Loss of superficial and deep somatic reflexes
      • Loss of visceral reflexes (e.g., micturition, defecation) as a result of bilateral sacral nerve root injury.

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    Central Nervous System Pain Control PDF

    Description

    Explore the intricacies of the central nervous system (CNS) and its role in pain control mechanisms. This quiz covers the processes involved in pain suppression at various levels of the CNS, including the influence of opioid peptides. Understand how emotional stimuli and stress impact pain perception.

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