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Physio II: Exam 1 > L5: Sensory Pathways > Flashcards

L5: Sensory Pathways Flashcards

1
Q

most ascending pathways are made up of 3 orders of neurons

A

primary sensory neurons

secondary neurons

tertiary neurons

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2
Q

primary sensory neurons

A

originate from peripheral receptors such as merkel’s receptors

enter spinal cord/brain via dorsal roots (cranial nerves)

cell bodies located in dorsal root ganglia

synapse in spinal cord w/ 2ndary neurons

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3
Q

secondary neurons

A

originate in spinal cord gray matter

travel thru spinal cord in myelinated columns

make up tracts in spinal cord and brainstem

decussate (cross over)

synapse in thalamus w/ tertiary neurons

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4
Q

tertiary neurons

A

travel from thalamus to primary sensory cortex

travel thru internal capsule

terminate in somatosensory cortex

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5
Q

internal capsule

A

myelinated pathway between thalamus and some of the basal nuclei

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6
Q

ascending pathways for conscious perception

A

spinothalamic system

  • –lateral spinothalamic tract
  • –ant. spinothalamic tract

medial lemniscal system

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7
Q

ascending pathways for unconscious perception

A

spinocerebellar
spino-olivary
spinotectal
spinoreticular

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8
Q

laternal spinothalamic tract carriers? (LST)

A

pain and temperature

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9
Q

primary fibers – lateral spinothalamic tract

A

ascend or descend 1-2 spinal cord segments before synapsing w/ secondary fibers

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10
Q

secondary fibers – lateral spinothalamic tract

A

decussate thru anterior gray and white commissures

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11
Q

secondary axons – lateral spinothalamic tract

A

make up the lat. spinothalamic tract traveling in the lateral column of the spinal cord

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12
Q

LST secondary fibers are joined in brainstem by ?

A

fibers of the trigeminothalamic tract

pain and temperature from face and teeth

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13
Q

LST secondary fiber collaterals project to ?

A

reticular formation

stimulate wakefulness and consciousness

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14
Q

LST secondary fibers project to VPL of ?

A

ventral postlateral nucleus of thalamus

synapse w/ tertiary fibers in VPL

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15
Q

corticopetal fibers synapse ?

A

(tertiary fibers)
in postcentral gyrus
somatic sensory areas 3, 1, 2

tertiary fibers form part of internal capsule

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16
Q

anterior spinothalamic tract (AST) carriers?

A

light touch - crude touch
pressure
tickle
itch

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17
Q

AST primary neurons

A

may ascend 8-10 spinal cord segments before synapsing w/ 2ndary neurons

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18
Q

AST 2ndary neurons

A

decussate in ant. gray or white commissures

ascend to synapse w/ tertiary fibers in VPL nucleus of thalamus

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19
Q

AST tertiary fibers

A

ascend thru internal capsule to primary sensory cortex

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20
Q

dorsal column-medial lemniscal pathway carriers?

A

also called post. column system (PCS)

2 pt sensation - fine touch
pressure
vibration

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21
Q

2 point discrimination

A

touch that refers to ability to distinguish 2 separate points as close as 2 mm apart

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22
Q

PCS primary fibers

A

ascend entire length of spinal cord

synapse w/ 2ndary neurons in medulla

  • –fasciculus gracilis
  • –fasciculus cuneatus
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23
Q

PCS axons from lower limbs travel in the _____ portions of the 2 _____ _____ .

A

medial portions
2 dorsal columns

each area of dorsal column called = fasciculus gracilis

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24
Q

fibers of fasciculus gracilis

A

synapse in nucleus gracilis and convey sensations from below midthoracic level

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25
PCS axons from upper limbs travel in ____ portion of the 2 ____ ____.
lateral portion 2 dorsal columns each area of dorsal column called = fasciculus cuneatus
26
fibers of fasciculus cuneatus
synapse in nucleus cuneatus convey sensations from above midthoracic level also convey proprioceptive sensation from arms to cerebellum
27
PCS 2ndary fibers
decussate | ascend to synapse in VPL of thalamus
28
PCS tertiary fibers
ascend thru internal capsule to primary sensory cortex
29
which neurons/fibers decussate? primary 2ndary tertiary
2ndary
30
Brodmann's area 1,2,3
primary somatosensory area
31
Brodmann's area 5,7
somatosensory association
32
somatosensory area I
located posterior central sulcus
33
widespread bilateral excision of somatosensory area I
1. loss of ability to localize sensations to dif. body parts 2. cannot judge critical degrees of pressure 3. cannot judge weights of objects 4. cannot judge shapes or forms 5. cannot judge texture of materials pain and temp. senses are still preserved but poorly localized
34
somatosensory area II receives signals from ?
brain stem -- transmitted upward from both sides of bodies secondarily from area I other sensory areas of body - including visual and auditory
35
projections from somatosensory area ____ are required for function of somatosensory area ____.
I II
36
removal of somatosensory area II ?
has no apparent effect on the response of neurons in somatosensory area I
37
number of layers of somatosensory cortex
six layers 1-2 superficial 5-6 deepest
38
layers 1-2 of somatosensory cortex
receive input signals from lower brain centers
39
layers 2-3 and 4 of somatosensory cortex
2-3 send info thru corpus callosum to other hemisphere 4 receives incoming sensory signals
40
layers 5-6 of somatosensory cortex
large neurons in 5 project to distant areas such as basal nuclei, brain stem and spinal cord axons from 6 project to thalamus
41
describe lateral inhibition
important in blocking the lateral spread of excitatory signals thereby increasing the degree of contrast in the cerebral cortex
42
lateral inhibition occurs ?
at each synaptic level 1. dorsal column nuclei 2. ventrobasal nuclei of thalamus 3. somatosensory cortex
43
pain receptors
nociceptors | free nerve endings
44
characteristics of fast pain
1. felt in 0.1 sec 2. not felt in deep tissues 3. generally elicited by mechanical and thermal stimuli 4. carried by Adelta pain fibers
45
termination of fast pain
pain fibers typically end in lamina I of dorsal horns of spinal cord
46
characteristics of slow pain
1. post 1 sec and increases 2. aching, slow burning, throbbing, nausea, chronic 3. elicited by mechanical, thermal, chemical stimuli
47
slow chronic pain is carried by ?
C type fibers | which usually terminated in layers 2-3 of dorsal horns of spinal cord
48
lamina I
lamina marginalis of dorsal horns of spinal cord
49
layers 2-3 of dorsal horns of spinal cord
substantia gelatinosa
50
pain travels thru ______ tracts
anterolateral
51
primary pain fibers synapse?
in dorsal horns of spinal cord w/ 2ndary fibers layers 1, 2, or 3
52
secondary pain fibers ?
immediately decussate make up the anterolateral pathways
53
neospinothalamic tracts
fast pain fibers make up this synapse and terminate in ventrobasal nuclei of thalamus
54
tertiary pain fibers
ascend to somatosensory cortex
55
paleospinothalamic tracts
made up of slow pain fibers most 2ndary fibers terminate thru out brainstem some pass to thalamus
56
the Adelta of fast pain use ____ as their NT.
glutamate
57
type C fibers of slow pain use what NT?
release glutamate and substance P g - instantaneous sub. p - slow
58
when does brown-Sequard syndrome occur?
a hemisection of the spinal cord partial slice thru
59
brown-Sequard syndrome results
1. all motor function blocked below section 2. spinothalamic path lost on opposite side of body in dermatomes below level 3. kinesthetic and position sensation, vibration, 2pt - lost on side of section in all dermatomes below
60
analgesia system
consists of 3 major components 1. periaqueductal gray and periventricular regions of brainstem and 3rd ventricle 2. raphe magnus nucleus and reticular nuclei in medulla 3. pain inhibitory complex in dorsal horns of spinal cord
61
thermal sensations
3 types of receptors -- cold, warmth, pain
62
what does analgesia mean?
stopping pain
63
warmth nerve endings
free nerve endings | mainly transmitted over C-type fibers
64
cold receptors
3-10x as numerous as warm small type Adelta myelinated endings
65
cold and warmth receptors are thought to be stimulated by ?
their change in metabolic rates
66
thermal signals are transmitted in ?
pathways parallel to those for pain signals
67
what is referred pain?
occurs when visceral pain fibers are stimulated and stimulate some of the pain fibers that conduct pain from the skin
68
when does severe pain result?
when there is diffuse stimulation of pain nerve endings thru out the viscera (ex. ischemia) as opposed to highly localized types of damage to viscera
69
all visceral pain from thorax and abdominal cavities travels?
via type C pain fibers
70
headaches are the result of ?
pain referred to the surface of the head from deep head structures
71
the brain and pain
the brain itself is almost completely insensitive to pain
72
visceral pain is only ?
chronic-aching-suffering type of pain

Physio II: Exam 1 (9 decks)

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