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Neuro > Powerpoint 1 > Flashcards

Powerpoint 1 Flashcards

1
Q

What is the neuronal circuit organization in the dorsal column pathway?

A

Divergence at each synaptic stage; stronger stimuli activate more neurons, especially in the central cortical field.

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2
Q

two-point discrimination, fine vs poor

A

Fine discrimination: 1-2 mm on fingertips;

Poorer discrimination: 30-70 mm on the back due to fewer tactile receptors.

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3
Q

What is lateral inhibition?

A

Enhances contrast by blocking lateral spread of excitatory signals.

Occurs at multiple levels: dorsal column nuclei, thalamus, and cortex

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4
Q

How are high frequency vibratory signals detected?

A

High-frequency vibrations (up to 700 cycles/sec) detected by Pacinian corpuscles

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5
Q

What encodes intensity in signal transmission?

A

Intensity is encoded by increased number of activated fibers and higher impulse rate in each fiber.

• Enables sensory systems to handle a wide range of stimulus intensities

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6
Q

What kinds of fibers make up the anterolateral system?

A

Composed of smaller myelinated (Aδ) and unmyelinated (C) fibers

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7
Q

What sensations does the anterolateral system transmit?

A

Transmits pain, temperature, and crude touch sensations.

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8
Q

Velocity of the anterolateral system

A

Slower conduction velocities (up to 40 m/sec)

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9
Q

Where are pain receptors located?

A

Free nerve endings are present in skin, periosteum, arterial walls, joint surfaces, and cranial vault.

Sparse in deep tissues. widespread damage can cause chronic, aching pain

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10
Q

What are the types of painful stimuli?

A

Mechanical, thermal, and chemical stimuli.

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11
Q

What is the role of bradykinin in pain sensitivity?

A

Bradykinin is particularly potent in eliciting pain.

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12
Q

How does pain receptor adaptation occur?

A

Minimal adaptation, often with hyperalgesia (increased sensitivity over time).

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13
Q

What causes pain from ischemia?

A

Pain from anaerobic byproducts like lactic acid.

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14
Q

What characterizes fast pain?

A

Felt within 0.1 seconds of stimulus; Sharp, pricking, acute, or electric pain.

Common stimuli: Needle prick, skin cut, acute burn.

Also limited to superficial tissues

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15
Q

What characterizes slow pain?

A

Begins 1 second or more after stimulus, increasing gradually; Burning, aching, throbbing, or chronic pain.

Associated with tissue destruction

Occurs in both superficial and deep tissues/ organs

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16
Q

What is referred pain?

A

Pain perceived in a location distant from the actual source of pain, often in a superficial area while the source is deep or visceral.

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17
Q

Why is referred pain clinically important?

A

Vital in diagnosing visceral ailments where referred pain may be the only symptom.

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18
Q

What is the mechanism behind referred pain?

A

Visceral pain fibers synapse on the same second-order neurons in the spinal cord that receive pain signals from the skin.

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19
Q

What are the challenges in localizing visceral pain?

A

Lack of direct experience with internal organs leads to poor localization; Dual pain pathways from visceral organs complicate localization.

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20
Q

What is the true visceral pathway?

A

Pain signals travel via autonomic nerves and are referred to surface areas far from the origin, based on embryonic origin.

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21
Q

What is the parietal pathway?

A

Pain signals from parietal peritoneum, pleura, or pericardium travel via local spinal nerves, localized directly over the affected area.

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22
Q

How is appendix pain referred?

A

Visceral pain is referred to the umbilical region (T10-T11) as aching/cramping; Parietal pain is sharp over the right lower quadrant.

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23
Q

Where does lateral inhibition of the dorsal column pathway occur?

A

Occurs at multiple levels: dorsal column nuclei, thalamus, and cortex.

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24
Q

How are lower frequency vibratory signals transmitted?

A

Lower frequencies (below 200 cycles/sec) detected by Meissner’s corpuscles.

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25
Q

How are lower frequency vibratory signals transmitted?

A

Lower frequencies (below 200 cycles/sec) detected by Meissner’s corpuscles.

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26
Q

What is an important test for dorsal column integrity in neuro exams?

A

Vibratory signal transmission

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27
Q

Where do anterolateral system fibers synapse, where do they cross, and how do they ascend?

A

Fibers synapse in the dorsal horns of the spinal cord and cross to the opposite side. Ascend in the anterolateral columns to the brain.

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28
Q

Anterolateral system is important for the perception of ________ and ______

A

Nociceptive signals and thermal stimuli

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29
Q

Anterolateral system provides _______ precise localization compared to the dorsal column system

A

less

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30
Q

Painful stimuli: Mechanical

A

Physical damage or pressure

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31
Q

Painful stimuli: Thermal

A

Heat, especially above 45°C, which also damages tissues

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32
Q

Painful stimuli: Chemical

A

Involves chemicals like bradykinin, serotonin, histamine, and potassium ions

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33
Q

How do potassium ions and proteolytic enzymes affect pain sensitivity?

A

Increase pain by enhancing nerve membrane permeability

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34
Q

What causes pain from muscle spasm?

A

Causes pain through direct stimulation and induced ischemia

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35
Q

“Perceived origin” of referred pain:

A

Pain from internal organs is “referred” to the skin because both signals share common neurons, leading the brain to perceive the sensation as originating from the skin

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36
Q

What are the two pathways for referred pain?

A

• True Visceral Pathway:
• Parietal Pathway:

37
Q

Diagnostic importance of Visceral pain:

A

• Visceral pain is often the only indicator of visceral inflammation, infection, or disease

38
Q

Two key differences of visceral pain from surface pain:

A

• Localized damage to viscera typically does not cause severe pain (e.g., gut incision)
• Diffuse stimulation of pain fibers, such as from ischemia, causes intense pain

39
Q

What are the parietal surfaces?

A

• Include parietal peritoneum, pleura, and pericardium
• Supplied with extensive pain innervation similar to the skin

40
Q

How is fast-sharp pain elicited?

A

Mechanical or thermal stimuli

41
Q

What fibers transmit fast-sharp pain and what is their speed?

A

• Transmitted via type Aδ fibers at 6-30 m/sec

42
Q

How is slow-chronic pain elicited?

A

• Primarily elicited by chemical stimuli (sometimes mechanical/thermal)

43
Q

What fibers transmit slow-chronic pain, and at what speed?

A

• Transmitted via type C fibers at 0.5-2 m/sec

44
Q

What is a cordotomy?

A

Cutting pain-conducting tracts (anterolateral quadrant) in the spinal cord to relieve intractable pain, typically for lower body pain

45
Q

Pain insensitive areas include:

A

Liver parenchyma, lung alveoli

46
Q

Pain sensitive areas include:

A

Liver capsule, bile ducts, bronchi, and parietal pleura

47
Q

What are the four causes of visceral pain?

A

Ischemia, Chemical damage, spasm of smooth muscle, and overdistension

48
Q

How does ischemia cause visceral pain?

A

Reduced blood supply leads to accumulation of acidic metabolic products

49
Q

How does chemical damage cause visceral pain?

A

Leakage of substances (e.g., gastric juice) causing severe peritoneal pain

50
Q

How does spasm of smooth muscle cause visceral pain?

A

Causes intermittent, cramping pain (e.g., in appendicitis, gallbladder disease)

51
Q

How does spasm of smooth muscle cause pain?

A

Causes intermittent, cramping pain (e.g., in appendicitis, gallbladder disease)

52
Q

How does overdistention cause visceral pain?

A

Overfilling of hollow organs may stretch tissues and collapse blood vessels, leading to pain

53
Q

How does overdistention cause visceral pain?

A

Overfilling of hollow organs may stretch tissues and collapse blood vessels, leading to pain

54
Q

Sharp Pain in Visceral Disease:

A

• When disease affects a viscus and spreads to the parietal surfaces, pain is felt more sharply

• Parietal pain is often well-localized over the affected area, unlike diffuse visceral pain

55
Q

What fibers make up the Neospinothalamic Tract?

A

o Composed of Aδ fibers

56
Q

Where do the fibers of the Neospinothalamic Tract synapse?

A

primarily in lamina I of the dorsal horns

57
Q

Where do fibers of Neospinothalamic Tract cross, ascend, and terminate?

A

In dorsal horn, fibers cross to the opposite side and ascend through the anterolateral columns to the thalamus

58
Q

Two functions of the Neospinothalamic Tract

A

o Transmits fast pain sensations (sharp, localized pain)
o Informs about the immediate presence and location of painful stimuli

59
Q

Neospinothalamic Tract velocities are fast or slow?

A

Fast—. 6 or 30 m/sec

Rapid reflexive responses to painful stimuli

60
Q

Transmission of thermal signals: (pathway)

A

• Upon entering the spinal cord, they travel a few segments in Lissauer’s tract and terminate in laminae I, II, and III
• Ascend in the anterolateral tract to the reticular formation and ventrobasal complex of the thalamus
• Some signals reach the somatic sensory cortex, though cortical removal reduces but doesn’t abolish temperature discrimination

61
Q

Thermal receptors likely respond to ____________ changes that affect intracellular chemical reactions

A

temperature-driven metabolic rate changes

• Temperature change rather than direct effect on nerve endings likely causes stimulation

62
Q

What are the two pathways for pain transmission?

A

• Neospinothalamic Tract: Transmits fast-sharp pain signals

• Paleospinothalamic Tract: Transmits slow-chronic pain signals

63
Q

Where do slow pain signals terminate?

A

• Slow pain signals terminate in the reticular areas of the brain stem and intralaminar nuclei of the thalamus

64
Q

Pain signals have a _______ effect

A

• Strong arousal effect, keeping the brain alert – explains difficulty sleeping during severe pain

65
Q

Lower brain centers (brain stem and thalamus) are essential for__________

A

Conscious pain perception

66
Q

The cortex helps in ________ pain quality

A

interpreting

67
Q

Paleospinothalamic Tract is made of what kind of fibers?

A

C fibers

68
Q

Where does the Paleospinothalamic Tract synapse?

A

lamina II and III of the dorsal horns

69
Q

Where do the Paleospinothalamic Tract fibers cross, ascend, and terminate?

A

synapse in lamina II and III of the dorsal horns

o Fibers cross to the opposite side and ascend through the anterolateral columns to the various brain areas, primarily the brainstem

70
Q

Two functions of the Paleospinothalamic Tract

A

o Transmits slow pain sensations (dull, aching pain)

o Contributes to emotional and autonomic responses to pain

71
Q

Is Paleospinothalamic Tract slow or fast?

A

o Slower conduction velocities (0.5-2 m/sec)

72
Q

Paleospinothalamic Tract localization/ pain perception

A

o Less precise localization, contributing to diffuse pain perception

73
Q

Cold receptors fiber type and velocity

A

• Type Aδ fibers, thinly myelinated, transmit signals at 20 m/sec
• Some type C fibers may also function as cold receptors, suggesting a role for free nerve endings

74
Q

Warmth receptors fiber type and velocity

A

• Likely free nerve endings, transmit signals via unmyelinated type C fibers at 0.4 to 2 m/sec

75
Q

Pain receptors re. temperature?

A

• Activated by extreme cold and heat

76
Q

• Thermal Receptor Adaptation:

A

• Cold receptors adapt significantly but not fully, responding more strongly to temperature changes than to constant exposure

77
Q

Double Pain Sensation:

A

• Immediate fast-sharp pain via Aδ fibers prompts quick reaction
• Delayed slow pain via C fibers grows over time, reinforcing need for relief

78
Q

• Pain Signal Processing in the Spinal Cord: Where does it enter?

A

• Entry: Pain fibers enter the spinal cord via dorsal spinal roots

79
Q

• Dual Processing Systems:

A

• Fast-sharp and slow-chronic pain signals are processed separately, with relay neurons in the dorsal horns

80
Q

• Analgesia System Components:

A

• Periaqueductal gray and periventricular areas in the mesencephalon and pons
• Raphe magnus nucleus and nucleus reticularis paragigantocellularis in the medulla
• Dorsal horn inhibitory complex in the spinal cord

81
Q

• Analgesia System Components:

A

• Periaqueductal gray and periventricular areas in the mesencephalon and pons
• Raphe magnus nucleus and nucleus reticularis paragigantocellularis in the medulla
• Dorsal horn inhibitory complex in the spinal cord

82
Q

Pain inhibition pathway

A

• Signals from periaqueductal gray → raphe magnus nucleus → dorsal horns of spinal cord

83
Q

Pain inhibition pathway

A

• Signals from periaqueductal gray → raphe magnus nucleus → dorsal horns of spinal cord

84
Q

RE. the pain inhibition pathway: Release of _____ in the spinal cord stimulates secretion of ________, which inhibits pain signals

A

• Serotonin release in the spinal cord stimulates enkephalin secretion, inhibiting pain signals

85
Q

The two key neurotransmitters for pain suppression

A

• Enkephalin and Serotonin

86
Q

• Natural opiate-like substances

A

β-endorphin, met-enkephalin, leu-enkephalin, and dynorphin

87
Q

• Peripheral Tactile Stimulation

A

Rubbing skin near painful areas activates Aβ fibers, providing pain relief through lateral inhibition

88
Q

• Electrical Stimulation Techniques

A

Electrodes on the skin, spinal cord, or brain regions (e.g., thalamus, periventricular, periaqueductal areas) for pain control

89
Q

• Thermal Sensations: gradations

A

• Gradations: Freezing cold, cold, cool, indifferent, warm, hot, burning hot

• Extreme temperatures can stimulate pain receptors, creating sensations of freezing cold or burning hot

Neuro (4 decks)

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