Transcript Slow pain

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‫درد‬
‫و‬
‫قشر های حسی و حرکتی‬
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Types of Pain
• Fast Pain
• Slow Pain
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Pain Perception
• Fast pain: sharp and well localized, transmitted by
myelinated axons
• Slow pain: dull aching sensation, not well localized,
transmitted by unmyelinated axons
• Visceral pain: not as well localized as pain originating
from the skin  pain impulses travel on secondary
axons dedicated to the somatic afferents  referred
pain
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Fast Pain Pathway
Ventrobasal
Nucleus
Lamina
Marginalis
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II
IV
III VI
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VII
Anterolateral
Pathway
Substantia
Gelatinosa
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VIII
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Slow Pain Pathway
Ventrobasal
Nucleus
Lamina
Marginalis
I
II
IV
III VI
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VII
Substantia
Gelatinosa
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Anterolateral
Pathway
VIII
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Types of Neurons
• Afferent (Ascending) – transmit impulses from
the periphery to the brain
– First Order neuron
– Second Order neuron
– Third Order neuron
• Efferent (Descending) – transmit impulses
from the brain to the periphery
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Pain and Temperature
(Anterolateral System )
Cerebral Cortex
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Thalmus
Spinal cord
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Nociceptors = specialized terminal
peripheral branches of sensory nerve fibers
that are sensitive to noxious stimuli
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Pain Mediators
• Result from tissue
damage, inflammation
or ischemic changes in
the tissues provoking
the chemical
stimulation of nerves.
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Theories of Pain
• 1) Specificity Theory
• 2) Pattern Theory
• 3) Gate Control Theory
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Theories/ The Specificity Theory
• - pain is a sensation, like vision or
hearing, conveyed via unique
anatomical structures
• Evidence for specificity theory:
existence of nociceptors
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Theories/ The Pattern Theory
• Pain results from a pattern of
intense activity of neurons that also
can encode subtle sensations such as
warmth or fine touch
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Gate Control Theory
• Melzack & Wall, 1982
• Substantia Gelatinosa (SG) in dorsal horn of spinal
cord acts as a ‘gate’ – only allows one type of
impulses to connect with the SON
• Transmission Cell (T-cell) – distal end of the SON
• If A-beta neurons are stimulated – SG is activated
which closes the gate to A-delta & C neurons
• If A-delta & C neurons are stimulated – SG is blocked
which closes the gate to A-beta neurons
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Gate Control Theory
• Spinal cord areas that receive messages from
pain receptors, also receive input from other skin
receptors and from axons descending from the
brain
• these other inputs sometimes close the “gates”
for the pain mesages.
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Melzack & Wall (1982)
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Gate Control Model (1)
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Gate Control Theory (1)
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PAIN INHIBITORY COMPLEX: Presynaptic
Inhibition
BRAIN STEM.NEURON
ANTEROLATERAL
PATHWAY
INHIBITORY NEURON
PAIN
RECEPTOR
+
DORSAL HORN OF
SPINAL CORD
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PAIN INHIBITORY COMPLEX: Postsynaptic
Inhibition
BRAIN STEM.NEURON
ANTEROLATERAL
PATHWAY
INHIBITORY NEURON
PAIN
RECEPTOR
+
DORSAL HORN OF
SPINAL CORD
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Gate Control Theory (1,2)
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Gate control Model (2)
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Other Considerations
• Drugs can suppress pain sensitivity or block pathway
• Analgesia : No sensation
• Hypalgesia (Analgesia) : Decreased pain (higher
threshold)
• Hyperalgesia : Increased pain (lower threshold)
• Referred pain: one site has pain but felt in another site
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The Analgesia System
• 1) Periaquaductal Gray
• 2a) Lateral Tegmental Nucleus
• 2b) Locus Ceruleus
• 2c) Raphe Magnus Nucleus
• 3) Pain inhibitory complex in dorsal horns
(Substantia Gelatinosa)
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Stress Induced Analgesia
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Hyperalgesia
• Primary Hyperalgesia – due to
injury (sensory receptor level)
• Secondary Hyperalgesia – due to
spreading of chemical mediators
(CNS level-injury of Spinal Cord &
Thalamus)
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Referred Pain
•Dermatomal Theory
•Convergence Theory
•Facilitation Theory
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Referred PAIN (Convergence Theory-1)
• Visceral pain fibers synapse on same
secondary neurons as receive pain fibers from
skin
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Referred pain
(Convergence Theory-2)
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Acupuncture
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Cerebral Cortex
Three kinds of functional areas:
Sensory areas – conscious awareness of sensation
Motor areas – control voluntary movement
Association areas – integrate diverse information,
communicate “associate” with the motor cortex and
sensory association areas to analyze input
‫ناحیه حسی پیکری ‪1‬‬
‫‪ ‬منطبق با نواحی ‪ 1‬و‪ 2‬و ‪ 3‬برودمن‬
‫‪ ‬در خلف شیار مرکزی و در شکنج پس مرکزی‬
‫‪ ‬موقعیت قسمتهای مختلف بدن در این ناحیه بسیاردقیق است‬
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Sensory Homunculus
Areas input
3b&1:information from receptors in the skin
3a&2:proprioceptive information from receptors in muscles
and joints
This information from the skin is further processed within area
1 and then combined with information from muscles and
joints in area 2
A small discrete lesion in area 1 impairs tactile discrimination
Whereas a small lesion in area 2 impairs the ability to recognize
the size and shape of a grasped object.
Inputs & outputs
The cells in areas 3a and 3b project their axons to areas 1 and 2
Most thalamic fibers terminate in areas 3a and 3b
Thalamic neurons send a small projection directly to
Brodmann’s areas 1,2
Primary
Somesthetic
Area
Thalmocortical
connection
(VPLc  S I)
Central region
--- cutaneous (3b, 1)
Peripheral region
--- deep (3a, 2)
Somatic sensory portions of the thalamus and their cortical
targets in postcentral gyrus
Connections within the somatosensory cortex establish
functional hierarchies
‫ضایعات ‪S -1‬‬
‫‪‬اختالل در مکان یابی دقیق حس‬
‫‪‬اختالل در درک میزان فشار‬
‫‪‬اختالل در درک وزن اشیا‬
‫‪‬اختالل در تشخیص قوام اشیا‬
‫‪ ‬گرافستزیا و استرئوگونوزیا‬
‫حس درد و حرارت معموال آسیب نمی بینند‬
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Lesion of Somatosensory Area I

The person is unable to localize discretely the different sensations in the
different parts of the body. However, he or she can localize these sensations
crudely
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It is clear that the brain stem, thalamus, or parts of the cerebral cortex not
normally considered to be concerned with somatic sensations can perform
some degree of localization
The person is unable to judge critical degrees of pressure against the body.

The person is unable to judge the weights of objects.
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The person is unable to judge shapes or forms of objects. This is called
astereognosis
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The person is unable to judge texture of materials
‫ناحیه حسی پیکری ‪2‬‬
‫‪ ‬در دیواره فوقانی شیار سیلویوس قرار دارد‬
‫‪‬سیگنالهایی از ساقه مغز‪ ،S1 ،‬نواحی بینایی و شنوایی وارد‬
‫این ناحیه می شوند‬
‫‪‬نمایش بخشهای مختلف بدن در ‪ S2‬همانند ‪ S1‬کامل نیست‬
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secondary Somatosensory Cortex (SII)
- SII is hidden in the upper bank of the lateral sulcus in the parietal
operculum and responds bilaterally to nonpainful and painful
somatosensory stimuli
- Perform higher order functions including sensorimotor
integration, integration of information from the two body halves,
attention, learning and memory
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Lesion of somatosensory area 2
o lesions in area 2 alter the ability to differentiate the
size and shape of objects
o Removal of SII causes severe impairment in the
discrimination of both shape and texture and
prevents to learning new tactile that based on shape
‫مناطق ارتباطی حسی پیکری‬
‫‪ ‬نواحی ‪ 5‬و ‪ 7‬برودمن هستند‬
‫‪ ‬ورودی هایی از ‪ S1‬و قشر بینایی و قشر شنوایی و هسته قاعده ای‬
‫شکمی تاالموس دریافت می کنند‬
‫‪ ‬ترکیب و کشف رمز اطالعات رسیده به منطقه حسی پیکری را بر‬
‫عهده دارد‬
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‫اختالل در ناحیه ارتباطی‬
‫حذف یک طرفه‪:‬‬
‫‪‬از بین رفتن توانایی تشخیص اشیا و اشکال پیچیده در سمت‬
‫مقابل بدن‬
‫‪‬بی توجه شدن نسبت به نیمه مقابل بدن )‪(Neglect‬‬
‫‪‬آمورفوسنتز )‪(AMORPHOSENTHESIS‬‬
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Lesion of somatosensory association area
Unilateral visual neglect
Layers of Neocortex
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I.
Molecular Layer
II.
External Granular Layer
III.
External Pyramidal Layer
IV.
Internal Granular Layer
V.
Internal Pyramidal Layer
Giant pyramidal cell of Betz
VI.
Golgi
Weigert
Nissl
Polymorphic Layer
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Input & output
Input & output
Motor Areas
primary Motor Area (M I)
Premotor Area (PM)
Supplementary Motor Area (SMA)
Frontal Eye Field
Motor Cortices
(1) The Primary Motor Cortex (Area 4)
(2) the Premotor Area (Area 6)
(3) the Supplementary Motor Area (Area 6)
(4) Frontal Eye Field or Orbitofrontal Area (Area 8)
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‫قشر حرکتی اولیه‬
‫‪ ‬دراولین چین خوردگی‬
‫لوب فرونتال در جلوی‬
‫شیار مرکزی‬
‫‪ ‬ناحیه ‪ 4‬برودمن‬
‫‪ ‬با حداقل شدت تحریکات‬
‫الکتریکی باعث ایجاد‬
‫حرکت می شود‬
‫‪ ‬دارای نقشه توپوگرافیک‬
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Motor Homunculus
‫سازماندهی سوماتوتوپیک‬
‫قشر حرکتی اولیه آدمک‬
‫حرکتی نامیده می شود‬
‫نیمی از قشر اولیه به کنترل‬
‫عضالت دست و تکلم‬
‫اختصاص دارد‬
‫استفاده یا عدم استفاده از‬
‫یک قسمت بدن اندازه آن را‬
‫در نقشه تحت تاثیر قرار‬
‫می دهد‬
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‫ناحیه حرکتی مکمل‬
‫‪ ‬در قسمت قدامی‬
‫قشر حرکتی و‬
‫بر روی سطح‬
‫میانی مغز(در‬
‫داخل شیار‬
‫طولی)‬
‫‪ ‬درناحیه ‪6‬‬
‫برودمن‬
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