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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
Q

PCS axons from upper limbs travel in ____ portion of the 2 ____ ____.

A

lateral portion
2 dorsal columns

each area of dorsal column called = fasciculus cuneatus

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26
Q

fibers of fasciculus cuneatus

A

synapse in nucleus cuneatus

convey sensations from above midthoracic level

also convey proprioceptive sensation from arms to cerebellum

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27
Q

PCS 2ndary fibers

A

decussate

ascend to synapse in VPL of thalamus

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28
Q

PCS tertiary fibers

A

ascend thru internal capsule to primary sensory cortex

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29
Q

which neurons/fibers decussate?
primary
2ndary
tertiary

A

2ndary

30
Q

Brodmann’s area 1,2,3

A

primary somatosensory area

31
Q

Brodmann’s area 5,7

A

somatosensory association

32
Q

somatosensory area I

A

located posterior central sulcus

33
Q

widespread bilateral excision of somatosensory area I

A
  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
Q

somatosensory area II receives signals from ?

A

brain stem – transmitted upward from both sides of bodies

secondarily from area I

other sensory areas of body - including visual and auditory

35
Q

projections from somatosensory area ____ are required for function of somatosensory area ____.

A

I

II

36
Q

removal of somatosensory area II ?

A

has no apparent effect on the response of neurons in somatosensory area I

37
Q

number of layers of somatosensory cortex

A

six layers
1-2 superficial
5-6 deepest

38
Q

layers 1-2 of somatosensory cortex

A

receive input signals from lower brain centers

39
Q

layers 2-3 and 4 of somatosensory cortex

A

2-3
send info thru corpus callosum to other hemisphere

4
receives incoming sensory signals

40
Q

layers 5-6 of somatosensory cortex

A

large neurons in 5
project to distant areas such as basal nuclei, brain stem and spinal cord

axons from 6 project to thalamus

41
Q

describe lateral inhibition

A

important in blocking the lateral spread of excitatory signals

thereby increasing the degree of contrast in the cerebral cortex

42
Q

lateral inhibition occurs ?

A

at each synaptic level

  1. dorsal column nuclei
  2. ventrobasal nuclei of thalamus
  3. somatosensory cortex
43
Q

pain receptors

A

nociceptors

free nerve endings

44
Q

characteristics of fast pain

A
  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
Q

termination of fast pain

A

pain fibers typically end in lamina I of dorsal horns of spinal cord

46
Q

characteristics of slow pain

A
  1. post 1 sec and increases
  2. aching, slow burning, throbbing, nausea, chronic
  3. elicited by mechanical, thermal, chemical stimuli
47
Q

slow chronic pain is carried by ?

A

C type fibers

which usually terminated in layers 2-3 of dorsal horns of spinal cord

48
Q

lamina I

A

lamina marginalis of dorsal horns of spinal cord

49
Q

layers 2-3 of dorsal horns of spinal cord

A

substantia gelatinosa

50
Q

pain travels thru ______ tracts

A

anterolateral

51
Q

primary pain fibers synapse?

A

in dorsal horns of spinal cord w/ 2ndary fibers

layers 1, 2, or 3

52
Q

secondary pain fibers ?

A

immediately decussate

make up the anterolateral pathways

53
Q

neospinothalamic tracts

A

fast pain fibers make up this

synapse and terminate in ventrobasal nuclei of thalamus

54
Q

tertiary pain fibers

A

ascend to somatosensory cortex

55
Q

paleospinothalamic tracts

A

made up of slow pain fibers

most 2ndary fibers terminate thru out brainstem
some pass to thalamus

56
Q

the Adelta of fast pain use ____ as their NT.

A

glutamate

57
Q

type C fibers of slow pain use what NT?

A

release glutamate and substance P

g - instantaneous
sub. p - slow

58
Q

when does brown-Sequard syndrome occur?

A

a hemisection of the spinal cord

partial slice thru

59
Q

brown-Sequard syndrome results

A
  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
Q

analgesia system

A

consists of 3 major components
1. periaqueductal gray and periventricular regions of brainstem and 3rd ventricle

  1. raphe magnus nucleus and reticular nuclei in medulla
  2. pain inhibitory complex in dorsal horns of spinal cord
61
Q

thermal sensations

A

3 types of receptors – cold, warmth, pain

62
Q

what does analgesia mean?

A

stopping pain

63
Q

warmth nerve endings

A

free nerve endings

mainly transmitted over C-type fibers

64
Q

cold receptors

A

3-10x as numerous as warm

small type Adelta myelinated endings

65
Q

cold and warmth receptors are thought to be stimulated by ?

A

their change in metabolic rates

66
Q

thermal signals are transmitted in ?

A

pathways parallel to those for pain signals

67
Q

what is referred pain?

A

occurs when visceral pain fibers are stimulated

and stimulate some of the pain fibers that conduct pain from the skin

68
Q

when does severe pain result?

A

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
Q

all visceral pain from thorax and abdominal cavities travels?

A

via type C pain fibers

70
Q

headaches are the result of ?

A

pain referred to the surface of the head from deep head structures

71
Q

the brain and pain

A

the brain itself is almost completely insensitive to pain

72
Q

visceral pain is only ?

A

chronic-aching-suffering type of pain

Physio II: Exam 1 (9 decks)

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