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MOHD2: Exam 3 > Neuro: Somatosensory Pathways > Flashcards

Neuro: Somatosensory Pathways Flashcards

1
Q

Lesions to the spinothalamic tract cause loss of pain and temperature on the ______ side of the body at the level of the lesion or below.

A

contralateral

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1
Q

Where is the sensory nucleus of CN V located? What structure is near it?

A

In the pons, lateral and adjacent to the motor nucleus of V

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2
Q

The ______ reflex involves an Aδ neuron crossing multiple spinal segments and is followed by a crossed extension reflex of the opposite limb.

A

withdrawal

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2
Q

Pain, temperature and crude touch 1st order neurons end where?

A

pain/temp in laminae I; crude touch in laminae I and V.

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2
Q

Fibers from the cuneocerebellar tract ascend to the medulla in the cuneate fasciculus for upper limb afferents, and synapse in the ______ ______ ______.

A

accessory cuneate nucleus

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3
Q

Because Aδ and C fibers ascend the spinal cord in _____ _____ before entering the dorsal horn, anaesthesia typically begins 1-2 segments below the level of a lesion.

A

Lissauer’s tract

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3
Q

Where are the emotional aspects of pain transmitted once the spinothalamic signal reaches the postcentral gyrus?

A

insula

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4
Q

Bilateral segment loss of pain and temperature, 1-2 segments below the site of lesion, results from a lesion where?

A

ventral white commissure

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4
Q

Ia and Ib afferents from muscle spindles and golgi tendon organs synapse on what nucleus before making their way to the cerebellum?

A

Clarke’s nucleus (nucleus dorsalis)

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5
Q

Exaggerated deep tendon reflexes (DTRs) indicate a lesion or disease that affects what pathway?

A

corticospinal (UMN) pathway

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6
Q

The ____ _____ reflex controls muscle tension by causing relaxation via interneuron inhibition of lower motor neurons (alpha motor neurons)

A

golgi tendon reflex

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6
Q

The sensory nucleus and tract that processes nonconscious proprioceptive information from the face and head, primarily the muscles of mastication, and also the facial/tongue muscles and periodontal ligament (bite force control)

A

mesencephalic nucleus of CN V (meV)

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7
Q

Where does pain from the teeth end in the trigeminal nucleus?

A

In the interpolar (middle) and rostral (oral) parts

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8
Q

The dorsal column system (DCML) transmits what kind of information to the thalamus?

A

tactile sensations, conscious proprioception (ie joint position, limb and trunk position) and kinesthesia

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8
Q

Crossed VTT and uncrossed DTT fibers form the ____ _______, which terminates in the VPM of the thalamus

A

trigeminal lemniscus

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9
Q

Lesion of the ____ ____ results in ipsilateral loss of 2-point discrimination, vibration sense, conscious proprioception and kinesthesia in body segments below the level of the lesion.

A

dorsal column

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11
Q

The ______ reflex controls muscle length by causing contraction via a type Ia afferent neuron and a lower motor neuron.

A

myotatic or stretch

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13
Q

Golgi tendon organ nociceptors send sensory information to the cerebellum via what type of nerve fiber?

A

Type Ib

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15
Q

The medial bundle of the spinal cord contains heavy myelinated ______ root fibers carrying what kind of sensations?

A

type I and II dorsal root fibers; carrying touch, pressure, muscle spindle, and tendon sensation

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16
Q

In the dorsal column system, ascending sacral fibers cable together more _____ while cervical fibers cable together more ______.

A

medially; laterally

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17
Q

Axons of neurons that curve ventromedially to cross the midline (sensory decussation) and ascend as the medial lemniscus are known as what

A

internal arcuate fibers

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18
Q

Positive Romberg’s sign suggests damage to the _____ ____.

A

dorsal column

19
Q

Pacinian and Meissner’s corpuscles are mechanoreceptors that send signal impulses via what type of nerve fiber?

A

Aβ

20
Q

The medial lemniscus ascends the spinal cord, decussates in the medulla, and ends in the ____ nucleus of the ______.

A

VPL; thalamus

21
Q

Two types of finely myelinated or non-myelinated fibers are _____ and ______.

A

Aδ and C fibers

21
Q

Most reflex pathways involve a small inhibitory or excitatory neuron called a(n) ________.

A

interneuron

23
Q

The lateral bundle of the spinal cord contains non-myelinated _______ root fibers carrying what kind of sensations?

A

Aδ and C dorsal root fibers; carrying pain, temperature and crude touch sensations

24
Q

The jaw-jerk reflex is difficult to elicit in healthy individuals but is exaggerated in lesions of what pathway? Specifically, what inputs are affected?

A

corticobulbar (UMN) pathway, specifically, inputs to the motor nucleus of V

25
Q

What is the only structure in the CNS that contains primary afferent cell bodies?

A

mesencephalic nucleus

26
Q

Ascending 1st order neurons in the DCML pathway synapse on 2nd order neurons in gracile nucleus for fibers arising from what spinal level?

A

T6 or below

27
Q

System that relays pain, temperature, and crude touch

A

spinothalamic system

28
Q

How does the somtaotopic organization of the spinothalamic system differ from that of the DCML?

A

spinothalamic - sacral levels are more lateral and cervical levels are more medial DCML - sacral levels are more medial and cervical levels are more lateral

28
Q

This pathway transmits nonconcious proprioception from Ib afferents of the lower limb to the ipsilateral cerebellum.

A

VSCT

29
Q

The mesencephalic nucleus sends some axons to the _____-______ _____, which transmits conscious proprioception about what?

A

supra-trigeminal nucleus; jaw and tongue position

31
Q

Lesions arising from within the spinal cord affect what fibers last? What is this phenomenon known as?

A

sacral fibers; “sacral sparing”

32
Q

Information coming from the ascending medial lemniscus is somatotopically organized by the ____ and transmitted to the primary somatosensory cortex in the _______ ____

A

thalamus; postcentral gyrus

33
Q

Most axons of neurons in the spinal nucleus decussate, then ascend in the _____, which projects to the thalamus in the VPM.

A

VTTT

34
Q

Spinothalamic tract neurons are mostly found in which laminae? Where do all their axons cross?

A

I, IV, V and VI; ventral white commissure

36
Q

What are the 3 options (termination patterns) for branches of DRG fibers?

A

1) ascend to the gracile or cuneate nuclei in the caudal medulla 2) contact second order neurons in the dorsal horn 3) end in the intermediate or ventral zones to participate in reflexes (ie, synapse with lower motor neurons)

38
Q

Lesion of the ____ ____ results in contralateral loss of 2-point discrimination, vibration sense, conscious proprioception and kinesthesia in body segments below the level of the lesion.

A

medial lemniscus

39
Q

Tract that relays information about muscle stretch and tension from the upper limb to the ipsilateral cerebellum.

A

cuneocerebellar tract

40
Q

What is the afferent neuron pathway of C fibers carrying aching and burning pain sensation?

A

substantia gelatinosa (lamina II) –> interneuron –> nucleus proprius

40
Q

It is very unusual to lose all sensations on one side of the face, since some discriminative touch axons from the main sensory nucleus remain uncrossed and ascend as the_____.

A

DTTT

42
Q

In the spinothalamic system, second order neurons are mostly crossed where?

A

in the spinal cord

43
Q

Where does the trigeminal nerve enter the brainstem?

A

At the pons, via the middle cerebellar peduncle

44
Q

Second-order neurons in gracile/cuneate nuclei decussate in the _______ to form the _____ ______, which travels to the thalamus.

A

medulla; medial lemniscus

46
Q

Muscle spindle nociceptors send sensory information to the cerebellum via what type of fiber?

A

Type Ia

47
Q

All conscious trigeminal pathways converge on the ________ in the _______

A

VPM nucleus; thalamus

48
Q

The ______ _______ conveys pain, temp and crude touch from the face, head, nasal, and oral cavities. It is composed of 1st order Aδ and C fibers running downward to terminate on 2nd order neurons in the ______ ________.

A

Spinal tract; spinal nucleus

49
Q

Tract that arises from Clarke’s nucleus and relays information about muscle stretch and tension from the lower limbs and trunk to the ipsilateral cerebellum.

A

DSCT

51
Q

Pain, temperature, discriminative touch and proprioception signals from the head/face are relayed via what system?

A

Trigeminal sensory complex

52
Q

The sensory nucleus of CN V receives all 1st order discriminative touch sensations with which exception?

A

Does not receive proprioception sensation information

53
Q

What is the major output target of the mesencephalic nucleus?

A

motor nucleus of CN V (moV)

54
Q

Where do spinothalamic tract nerve fibers end?

A

in the VPL, as well as other thalamic nuclei

MOHD2: Exam 3 (10 decks)

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