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Physiology II E1 > L5 T1 Sensory pathways > Flashcards

L5 T1 Sensory pathways Flashcards

1
Q

Ascending pathways are made up of what three orders of neurons?

A

Primary sensory, secondary, and tertiary.

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2
Q

Where do primary sensory neurons enter the spinal cord?

A

Dorsal roots of spinal (cranial) nerves

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3
Q

Where are the cell bodies of primary sensory neurons located?

A

dorsal root ganglia

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4
Q

With what do the primary sensory neurons synapse in the spinal cord?

A

Secondary neurons

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5
Q

Where do the primary sensory neurons originated from?

A

peripheral receptors such as Merkel’s discs.

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6
Q

Where do secondary neurons originate?

A

Spinal cord gray matter

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7
Q

Secondary neurons make up ______ in spinal cord and brainstem.

A

tracts

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8
Q

Do secondary neurons travel through the spinal cord in myelinated or unmyelinated columns?

A

myelinated

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9
Q

True/False: Secondary neurons do not decussate.

A

False. Secondary neurons DO decussate.

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10
Q

Where, and with what do secondary neurons synapse

A

thalamus; tertiary neurons

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11
Q

Tertiary neurons travel from thalamus, through what, to what?

A

Through the internal capsule to the primary sensory cortex.

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12
Q

What location to the tertiary neurons terminate?

A

Somatosensory cortex

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13
Q

What is the internal capsule in which tertiary neurons travel?

A

Myelinated pathway between thalamus and some of the basal nuclei

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14
Q

What two ascending pathways are used for conscious perception?

A

Spinothalamic system (divided into lateral spinothalamic tract and anterior spinothalamic tract), and medial lemniscal system.

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15
Q

What are the four ascending pathways for unconscious perception?

A

Spinocerebellar, spino-olivary, spinotectal, and spinoreticular

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16
Q

Where do all of the ascending pathways for unconscious perception originate?

A

Spinal cord, and go to different parts of the brainstem

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17
Q

What does the lateral spinothalamic tract carry?

A

Pain and temperature

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18
Q

Primary fibers ascend or descend how many spinal cord segments before synapsing with secondary fibers in the lateral tract?

A

1-2

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19
Q

What type of axons make up the lateral spinothalamic tract traveling in the lateral column of the spinal cord?

A

secondary axons

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20
Q

Secondary fibers that are joined in the brainstem by fibers of trigeminothalamic tract carry what?

A

pain and temperature from the face and teeth

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21
Q

What is the function of secondary collaterals projecting to the reticular formation?

A

Stimulate wakefulness and consciousness

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22
Q

Where do tertiary fibers synapse?

A

postcentral gyrus

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23
Q

From what do the tertiary fibers form?

A

part of the internal capsule

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24
Q

Anterior spinothalamic tract neurons carry what sensation?

A

Crude/light touch, pressure, tickle, and itch

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25
Q

Primary neurons of the anterior spinothalamic tract ascend how many spinal cord segments before they synapse with secondary neurons?

A

8-10

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26
Q

In reference to anterior spinothalamic tract secondary fibers, where do they decussate?

A

anterior gray or white commissures

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27
Q

The dorsal column-medial lemniscal pathway systems carries sensations for what?

A

two-point sensation (fine touch), pressure and vibration.

28
Q

What is two point discrimination?

A

refers to the ability to distinguish two separate points as close as two millimeters apart.

29
Q

Lemniscal primary fibers ascend…..and synapse with…..

A

ascend the entire length of the spinal cord; synapse with the secondary neurons in medulla.

30
Q

Where do fibers of the fasciculus gracilis synapse? what to they carry?

A

they synapse in the nucleus gracilis and convey sensations from below midthoracic level.

31
Q

Where do fibers of the fasciculus cutaneous synapse? what to they carry?

A

they synapse in the nucleus cutaneous and convey sensations from above the midthoracic level.

32
Q

What neurons decussate?

A

Secondary

33
Q

The primary somatosensory area is made up of which Brodmann’s areas?

A

1, 2, and 3

34
Q

The somatosensory association area is made up of which Brodmann’s areas?

A

5 and 7

35
Q

Somatosensory area II receives signals from:

A
  • brainstem, transmitted upward from both sides of the body
  • secondarily from somatosensory area I
  • other sensory areas of the body, including visual and auditory
36
Q

True/False: Projections from somatosensory area I are required for function of somatosensory area II.

A

True

37
Q

True/False: Removal of somatosensory II has no apparent effect on the response of neurons in somatosensory area I.

A

True

38
Q

What is the function of layers I and II (the superficial layers) of the somatosensory cortex?

A

receive input signals from lower brain centers

39
Q

What is the function of layers II and III of the somatosensory cortex?

A

Send information through the corpus callosum to opposite hemisphere.

40
Q

What is the function of layers V and VI (deepest layers) of the somatosensory cortex?

A
  • large neurons in layer V project to distant areas such as basal nuclei, brainstem, and spinal cord.
  • axons from layer VI project to thalamus
41
Q

What is the function of layer IV of the somatosensory cortex?

A

receives incoming sensory signals

42
Q

What is lateral inhibition?

A

It is important in blocking the lateral spread of excitatory signals, thereby increasing the degree of contrast in the cerebral cortex. It helps to sharpen the incoming signal.

43
Q

Where does lateral inhibition occur?

A

at each synaptic level

  • dorsal column nuclei
  • ventrobasal nuclei of thalamus
  • somatosensory cortex
44
Q

Pain receptors are made of what?

A

free nerve endings

45
Q

What are the characteristics of fast pain?

A
  • felt quickly (0.1 seconds) after stimuli
  • not felt in most deeper tissues
  • generally elicited by mechanical and thermal stimuli
  • typically carried by Adelta fibers
46
Q

Where do pain fibers typically terminate?

A

in the lamina I of the dorsal horns of the spinal cord.

47
Q

What are the characteristics of slow pain?

A
  • begins approx. 1 second after stimulus is applied and increases over several seconds
  • described as aching, slow burning, throbbing, nauseous, and chronic
  • can be elicited by mechanical, thermal, and chemical stimuli.
48
Q

Fast pain is typically carried by what?

A

by A-delta fibers

49
Q

Slow pain is typically carried by what?

A

by C type fibers

50
Q

Where do slow pain fibers typically terminate?

A

in layers II and III of the dorsal horns of the spinal cord.

51
Q

What tract does pain travel through?

A

anterolateral tracts

52
Q

Primary pain fibers synapse where with secondary fibers?

A

in the dorsal horns of the spinal cord

53
Q

Once the primary pain fibers synapse with the secondary fibers, the secondary fibers immediately ________ and make their way up the ___________ pathways.

A

decussate; anterolateral

54
Q

Fast pain fibers make up what tract and synapse and terminate in the ventrobasal nuclei of the thalamus?

A

neospinothalamic

55
Q

Slow pain fibers make up what tract?

A

paleospinthalamic

56
Q

The A-delta fibers of the fast-pain path use which neurotransmitter?

A

glutamate

57
Q

Type C pain fibers use what two neurotransmitters?

A

glutamate - acts instantaneously

Substance P - released more slowly

58
Q

Pain travels through what tract?

A

anterolateral

59
Q

What are the components of the analgesia system?

A
  • periaquaductal gray and periventricular regions of brainstem and third ventricle
  • raphe magnus nucleus and reticular nuclei in medulla
  • pain inhibitory complex in dorsal horns of spinal cord
60
Q

What are the three receptors that discriminate thermal gradations?

A

cold, warmth, pain

61
Q

Warmth nerve endings are mainly transmitted by what type of fiber?

A

C type fibers

62
Q

Cold receptors are 3-10 times as numerous as warm nerve receptors and are what type of fiber?

A

small type A-delta myelinated endings

63
Q

True/False: Thermal signals are not transmitted in pathways parallel to those for pain signals.

A

False; thermal signals ARE transmitted in pathways parallel to those for pain signals

64
Q

When does referred pain occur?

A

occurs when visceral pain fibers are stimulated and stimulate some of the pain fibers that conduct pain signals from the skin.

65
Q

When does severe referred pain occur?

A

Severe pain results when there is diffuse stimulation of pain nerve endings throughout the viscera (as opposed to highly localized types of damage to the viscera).

66
Q

All visceral pain from the thoracic and abdominal cavities is transmitted via what type of pain fiber?

A

type C pain fibers

67
Q

__________ are the result of pain referred to the surface of the head from deep head structures.

A

Headaches

Physiology II E1 (9 decks)

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