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Neuroanatomy > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

What are the three main mechanisms to keep cerebral blood flow constant?

A
  1. autoregulation: vessels are stretch sensitive, so they constrict when pressure drops, and dilates when pressure increases
  2. Collaboration of brain and vessels, response to increased brain activity (glutamate sensing)
  3. cerebral vascular autonomics (may be more important at extremes of auto regulatory range)
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2
Q

What type of receptors detect mechanical, chemical, or thermal changes.

A

somatosensory receptors

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3
Q

All somatosensory receptors are ___ neurons with a cell body in DRG or cranial nerve ganglion, a CNS process, and a peripheral process with an ending in skin, muscle, or a joint.

A

pseudounipolar neurons

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4
Q

The skin is richly innervated with a variety of endings broadly divided into encapsulated and non encapsulated receptors known as ___.

A

cutaneous receptors

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5
Q

What are the three encapsulated cutaneous receptors?

A
  1. pancinian corpuscle: rapid (vibrations)
  2. meissner corpuscle: rapid (touch)
  3. ruffini ending: slow (pressure)
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6
Q

What are the three non encapsulated types of cutaneous receptors?

A
  1. endings around hairs: rapid (touch)
  2. merkel endings: slow (touch)
  3. free nerve endings: varies (pain, temp, itch, touch)
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7
Q

Receptor endings wrap around hairs. Their nerve ending is found at a ___ in the basal layer of the skin.

A

merkel cell

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8
Q

What are the type of receptors in glabrous (hairless skin)?

A
  • meissner corpuscle
  • merkel cells
  • pancinian corpuscle
  • ruffini ending
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9
Q

___ are responsible for discriminative touch (two point discrimination) which is concentrated in the finger tips. They use A-beta fibers which are fast conducting.

A

Meissner corpuscle

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10
Q

___ are also used to sense discriminative touch (two point discrimination) but they are responsible for fine touch detail. They sense edges of objects and texture.

A

Merkel nerve ending (also A-beta fiber which are fast conducting)

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11
Q

Where is the pathway for discriminative touch found?

A

posterior column- medial lemniscal pathway

  • two point discrimination
  • conscious proprioception
  • vibratory sense
    • A-beta fiber
    • collateral to lamina II
  • decussates in the medulla
  • relays in lateral thalamus
    • ventral posterolateral nucleus (VPL)
  • terminates in postcentral gyrus
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12
Q

The ___ of stimulus correlates with the number of cutaneous receptors

A

spatial resolution

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13
Q

There are more ___ and ___/cm^2 in the finger tip than in the hand so two point discrimination is more sensitive in the finger tip.

A

meissner corpuscles and merkel endings

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14
Q

___ detect vibration and are concentrated in the fingers and in the palm. They use A-beta fibers so they are fast conducting

A

pancinian corpuscle

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15
Q

___ are responsible for the sensation of pain, crude touch, and temperature.

A

free nerve endings (nociceptors, thermoreceptors, and some mechanoreceptors)

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16
Q

___ can be myelinated or unmyelinated fibers

A

free nerve endings

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17
Q

Temp sensitivity is due to ___ that open with a specific range of temperatures.

A

channels

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18
Q

What are the two phases of pain and briefly describe them.

A
  1. sharp prick, well-localized, short duration- carried by rapidly conducting myelinated fibers called fast or delta pain.
  2. slow, poorly localized, aching pain that may follow- carried by unmyelinated fibers, called slow pain.
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19
Q

The ___ and ___ pathways have well defined locations in spinal cord white matter

A

ascending and descending

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20
Q

Describe the three general types of ascending and descending pathways

A
  1. long, ascending fibers going to the thalamus, cerebellum, or various brainstem nuclei
  2. long, descending fibers going from cerebral cortex or various brainstem nuclei to spinal cord gray matter
  3. short, propriospinal fibers interconnecting different spinal cord levels (these fibers help coordinate flexor reflexes)
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21
Q

Descending tracts are primarily located in ___ and ___ in the spinal cord.

A

anterior funiculi and lateral funiculi

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22
Q

Ascending tracts are found in ___.

A

all three funiculi (AF, LF, PF)

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23
Q

___ fibers surround the spinal cord gray matter

A

propriospinal fibers

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24
Q

In the posterior column of the spinal cord, the ___ conveys touch and limb position information.

A

medial lemniscus

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25
Q

The ___ are mostly ascending large myelinated primary afferents from various mechanoreceptors.

A

posterior columns (main way info from cutaneous, joint, and muscle receptors reach the cortex)

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26
Q

Spinal ___ have their cell bodies in ipsilateral DRGs

A

afferents

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27
Q

As DRG rootlets enter cord, fibers divide into two divisions ___ and ___. Describe each. (medial lemniscus system)

A
  • Medial: heavily myelinated, larger diameter fibers; enter posterior column and ascend to the brainstem
  • Lateral: finely myelinated and unmyelinated, small diameter fibers
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28
Q

Rostral to T6 there are a few fibers added to ___ and ___ starts to form. (medial lemniscus system)

A

fasiculus gracilis

fasiculus cuneatus

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29
Q

Fibers entering the posterior columns of the medial lemniscus system are added ___ to those already present, so a pattern of lamination develops

A

laterally

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30
Q

The fibers of the medial lemniscus system are most medial at ___ levels and most lateral at ___ levels

A

sacral

cervical

31
Q

___ organization is typical of sensory and motor pathways in the posterior column medial lemniscus system.

A

somatotopic

32
Q

Fibers from the posterior column medial lemniscus system reach the brainstem and synapse in the ___ and ___.

A

nucleus gracilis and cuneatus (posterior column nuclei)

33
Q

Second order fibers cross the midline in the ___ and form the medial lemniscus

A

caudal medulla

34
Q

Third order fibers originate in the ___ ascend through the internal capsule and synapse in primary somatosensory cortex in ___.

A

thalamus (ventral posterolateral nucleus)

postcentral gyrus

35
Q

The medial lemniscus system maintains information related to ___ and ___ of a stimulus.

A

location and nature

36
Q

The ___ carries info important for conscious appreciation of touch, pressure, vibration, joint position/movement

A

medial lemniscus system

37
Q

Injury of the medial lemniscus leads to impaired ____ and discriminative tactile functions, especially complex tactile discrimination.

A

proprioception

38
Q

The ___ is tested clinically by placing a vibrating tuning fork on body surface or have patient identify a pattern drawn on their skin

A

medial lemniscus system

39
Q

___ can be lost completely after posterior column injury, can result in ___; uncoordinated movements as brain is unable to direct motor activity without feedback from the body.

A
  • proprioception

- ataxia

40
Q

Sensory info reaches the brain in multiple pathways, so the damage to a single pathway rarely leads to total loss in function, however the ability to discriminate ___ of an object or ___ or ___ of the stimulus moving across the skin will likely remain impaired

A

complex shape (stereognosis)
direction
speed

41
Q

Describe the spinothalamic tract

A
  • one of multiple pathways that convey pain and temperature info.
  • involved in awareness and localization of painful stimuli
  • ultimately ends in VPL of thalamus and some nearby thalamic nuclei
42
Q

Describe the anterolateral pathway

A

Other pain pathways end in reticular formation or limbic system to mediate other pain responses, these tracts and the spinothalamic tract together are known as the anterolateral pathway.

43
Q

where is the anterolateral pathway located?

A

anterior half of lateral funiculus

44
Q

Pain, temp, and some mechanoreceptor fibers enter the cord via the lateral division of ___, project branches to ___ horn, and may synapse in ___. (anterolateral pathway)

A

dorsal root
posterior
substantia gelatinosa

45
Q

Neurons in other laminae form 2nd order neurons and cross the midline with ___ inclination, collect and form the ___.

A

rostral

anterolateral pathway

46
Q

new fibers join the anterolateral pathway at the ___.

A

anteromedial edge

47
Q

Describe the somatotopic organization of the anterolateral pathway

A
  • caudal body parts in posterolateral portion

- rostral body parts in anteromedial portion

48
Q

In the anterolateral pathway, the spinothalamic fibers start in ___ an ___, project to the ventral posterolateral nucleus of the thalamus (VPL)

A

laminae I and laminae V

49
Q

The ___ is responsible for conscious awareness of pain and temperature; nature (burn, sting, etc) and location

A

anterolateral pathway

50
Q

polysynaptic projections to brainstem reticular formation are known as ___.

A

spinoreticular fibers (likely important for changes in the level of attention of pain response)

51
Q

___ fibers (also from laminae I and V) are important in pain control mechanisms

A

spinomesencephalic fibers

52
Q

___ fibers mediate autonomic response to pain

A

spinohypothalamic

53
Q

Damage to the ___ causes loss of pain, temp, itch, and tickle sensations

A

anterolateral pathway

54
Q

Bowel, bladder pressure, and sexual sensations ascend ___ so ___ injury does not leave a deficit

A

bilaterally

unilateral

55
Q

The motor cortex is located on the ___

A

precentral gyrus

56
Q

The somatic sensory cortex is located on the ___

A

postcentral gyrus

57
Q

___ is a procedure that destroys spinothalamic tract to produce contralateral analgesia in patients with intractable pain.

A

cordotomy

58
Q

Describe where to cut during a cordotomy.

A

cut lateral funiculus from dentate ligament to ventral root rostral to highest dermatomal pain level

59
Q

Information from the spinal cord is used by the ___ to coordinate movement

A

cerebellum

60
Q

The modes of transport from the spinal cord to the cerebellum can be ___ or ___.

A

direct: spinocerebellar tracts (3 are well characterized) or indirect: via brainstem relay nuclei

61
Q

The posterior spinocerebellar tract conveys ___ info.

A

proprioceptive

62
Q

In the PSCT, collaterals from the posterior columns convey tactile, pressure, and proprioceptive info (spindles and GTO). They synapse in ____.

A

Clarkes nucleus

63
Q

Axons ascend ipsilateral (same side) ___ forming the PSCT on the cord surface.

A

lateral funiculus

64
Q

Fibers of the PSCT enter the cerebellum (vermis and adjacent hemispheres) via ___.

A

inferior cerebellar peduncle

65
Q

___ does not exist caudal to about L2, so neither does the PSCT

A

Clarke’s

66
Q

___ from levels caudal to L2 ascend to L2 via the fascicles gracilis and synapse on Clarke’s nucleus

A

afferents

67
Q

Most spinocerebellar-like fibers that enter in cervical and upper thoracic segments do not project to ___.

A

clarke’s nucleus

68
Q

Arm afferents ascend in fascicles cuneatus to ___ in the medulla.

A

lateral cuneate nucleus

69
Q

Axons from lateral cuneate nucleus collect and form ___, which enters inferior cerebellar peduncle to synapse in vermis and nearby cerebellar hemispheres

A

cuneocerebellar tract

70
Q

The ___ conveys more complex information to the cerebellum and has its origins in the lateral surface of anterior horn at lumbar levels

A

anterior spinocerebellar tract

71
Q

The ___ activity is more related to attempted movement than simple sensory signals

A

anterior spincerebellar tract

72
Q

The ASCT crosses the midline twice, so the fibers end up ___ to their source.

A

ipsilateral

73
Q

All of the major spinocerebellar tracts enter the cerebellum through the inferior peduncle except ___.

A

ascending spinocerebellar tract

74
Q

The only spincerebellar tract to cross the midline is the ___.

A

ascending spinocerebellar tract

Neuroanatomy (6 decks)

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