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UM - Neuro Conditions > Ascending and Descending Tracts > Flashcards

Ascending and Descending Tracts Flashcards

1
Q

Define tract

A

A bundle of axons with the same origin and termination

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2
Q

What are the two types of pathways that bring afferent sensory info to the brain

A

Conscious Relay Pathways

Divergent Pathways

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3
Q

What is a conscious relay pathway

A

An afferent pathway that brings info about location and type of stimulus to the cerebral cortex
Discriminative touch & proprioception IPSI
Discrimitive pain & temp CL

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4
Q

What is a divergent pathway

A

An afferent sensory pathway that transmits sensory info to many locations in the BS and cortex - both conscious and unconscious
Ie - aching pain

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5
Q

What are unconscious relay pathways

A

Bring afferent unconscious proprioception and other movement related information to the cerebellum

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6
Q

What does the DCML transmit?

A

Discriminative
Proprioception
Vibration
Light moving touch

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7
Q

What do the anterolateral tracts transmit?

A 
Course/crude touch
Pain
Temperature
Sharp/dull
Tickle and itch
Sexual sensations
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8
Q

Receptors & pathway:

Discriminative touch

A

PCML

A delta, myelinated

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9
Q

Receptors & pathway:

Proprioception

A

PCML

Ia, Ib, II

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10
Q

Receptors & pathway:

Vibration

A

DCML

Pacinian corpuscles, Ia, Ib, II

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11
Q

Receptors & pathway:

Light moving tough

A

PCML

superficial mechanoreceptors

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12
Q

Receptors & pathway:

Course/crude touch

A

Anterolateral

C-fiber, unmyelinated

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13
Q

Receptors & pathway:

Pain

A

Anterolateral
Fast - A delta
Slow - C-fiber

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14
Q

Receptors & pathway:

Temperature

A

Anterolateral
Free nerve endings
myelinated and unmyelinated axons

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15
Q

Receptors & pathway:

Sharp/dull

A

Anterolateral

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16
Q

Receptors & pathway:

Tickle and itch

A

Superficial mechanoreceptors

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17
Q

Receptors & pathway:

Sexual sensations

A

Superficial mechanoreceptors

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18
Q

Lateral to medial organization of the lateral spinothalamic tract

A

Sacral
Lumbar
Thoracic
Cervical

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19
Q

Lateral to medial organization of the Lateral corticospinal tract

A

Sacral
Lumbar
Thoracic
Cervical

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20
Q

Lateral to medial organization of the DCML/PCML

A 
Cuneate fasciculus (Cervical)
Gracile fasciculus (Thoracic, Lumbar, Sacral)
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21
Q

What tracts comprise the ALS system?

A

Spinothalamic tract
Spinoreticular tract
Spinomesencephalic tract

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22
Q

PCML/DCML pathway - 1st order neurons

A

1st order neurons: (Receptors Ia phasic & tonics, Ibs) ascend IPSI and terminate at the nucleus gracile and cuneate of the lower medulla

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23
Q

PCML/DCML pathway - 2nd order neurons

A

2nd order neurons: Begin in caudal medulla - nucleus gracile and cuneate, decussate forming the ML, which ascends to the CL BS to project to the VPL nucleus of the thalamus

24
Q

PCML/DCML pathway - 3rd order neurons

A

Begin in the Ventral Posterolateral nucleus of the thalamus to then send axons through the posterior limb of the internal capsule to the somatosensory cortex - broadman areas 3,1,2

25
Q

Spinothalamic pathway - 1st order neurons

A

A delta & C fibers synapse on 2nd order neurons in the substantia gelatinosa or nucleus proprius

26
Q

What are “tract cells”

A

Travel 1-2 vertetbrae levels higher than the point of entry at the Lissauer’s tract - the substantia gelatinosa or nucleus proprius are examples

27
Q

Spinothalamic pathway - 2nd order neurons

A

Begin at the substantia gelatinosa or nucleus proprius and decussate in the anterior commisure, then ascend contralaterally in the anterolateral spinal cord to the rostral venterolateral medulla

28
Q

Spinothalamic pathway - Lateral spinothalamic tract

A

Ascends through the medulla and joins w/anterior spinothalamic tract to form the spinal lemniscus > midbrain ? thalamic nuclei (VPL, VPM, & medial doral)

29
Q

Spinothalamic pathway - 3rdorder neurons

A

Pass through the posterior limb of the internal capsule > corona radiate ? primary sensory cortex (Broadmann areas 3, 1, 2)

30
Q

Which broadman areas are associated with….

a) DCML
b) ALS

A

a) Broadman area 3

b) Broadman areas 1,2

31
Q

List the conscious pathways to the cerebral cortex

A

PCML

ALS (spinothalamic tract, Spinoreticular tract, Spinomesencephalic tract)

32
Q

Purpose of spinoreticular tract

A

Brings sensory info to the reticular formation - Arousal, attention, and sleep/waking cycles

33
Q

Spinoreticular tract

A

Enters the SC similar to spinothalamic tract & projects to the reticular formation

Reticular formation axons project to midline and to the intralainar nuclei of the thalamus

Then to many areas of the brain

34
Q

Purpose of the spinomesencephalic tract

A

Carries pain or nocicpetive sensory info to two areas in the brain and activates descending tracts to help control the pain

35
Q

Spinomesencephalic tract

A

Enters the SC similar to spinothalamic tract, projects to the superior colliculi (to turn eyes and head towards stimulus) and projects to periqeuductral gray matter around the cerebral aqueduct (activate descending tracts)

36
Q

List the Unconscious pathways to the Cerebellum

A

High fidelity tracts: Posterior spinocerebellar tract & Cuneocerebellar tract

Internal feedbacck tracts:
Anterior spinocerebellar tract & Rostrospinocerebellar tract

37
Q

What does the unconscious pathways to the cerebellum do?

A

Carry sensory afferent info to the cerebellum so we can quickly assign to perkinje cells of the cerebellum

38
Q

List the Descending spinal cord tracts

A 
Lateral corticospinal tract (CST)
Anterior CST
Rubrospinal tract
Reticulospinal tract (RST)
Medial and lateral vestibular spinal tracts (VST)
Tectospinal tracts
39
Q

What does the lateral CST do?

A

Controls voluntary movement, primarily of the distal hands and feet, but also all parts of the body

40
Q

Lateral CST

A

Begins in primary motor cortex > internal capsule > cerebral peduncles > anterior pons > pyramids of the medulla > lateral SC > alpha and gamma motor neurons

41
Q

What percentage of Lateral CST neurons cross?

A

88-90% cross in the lower medulla

42
Q

What does the anterior/medial CST do?

A

Controls voluntary movement, primarily of the head, neck & trunk, proximal joints (pelvis and scapula)

43
Q

What happens to the CST neurons that do not cross?

A

The 10-12% stay ipsilateral and descend in the ventral funiculus and then project to the alpha and gamma motor neurons of the ipsilateral, contralateral, and bilateral spinal cord

44
Q

T or F: The Rubrospinal tract is the same in cats and humans

A

False -
Cats: projects to UE and LE
Humans: UEs only

45
Q

Rubrospinal tract

A

Projects from frontal lobe and cerebellum, originatting in red nucleus > bentral horn alpha and gamma motor neurons & interneurons of cervical SC

46
Q

What does the rubrospinal neurons project to?

A

Shoulder, elbow & wrist mm (NOT DISTAL INTRINSIC HAND MM)

47
Q

Purpose of Reticulospinal tract (RST)

A

Facilitate bilateral LMN innervating postrual and gross motor movement throughout the entire body

48
Q

Medial Reticulospinal tract (RST)

A

Begins in reticular formation (pons and medulla)
Travoes length of SC to multiple neural segments bilaterally
Proximal axial & limb mm & to commissural interneurons for both sides of body

49
Q

Lateral Reticulospinal tract (RST)

A

Begins in reticular formation (pons and medulla)

More limited than Medial RST, travel at only a few neural levels on the IPSI side

50
Q

What is thought to be responsible for flexor withdrawl and crossed extension responses

A

Medial Reticulospinal tract (RST)

51
Q

What is thought to be responsible for CPG for locomtion

A

Lateral Reticulospinal tract (RST)

52
Q

What does the Medial Vestibulospinal tract project to?

A

Bilaterally project in the cervical and upper thoracic spinal segments & then to the proximal head and neck mm

53
Q

Medial vestibulospinal tract (inputs & origin)

A

Originates in medial vestibular nucleus and gets inputs from the emdial vestibular nucleus to the semicircular canals, utricle, and saccule

54
Q

What does the Lateral Vestibulospinal tract project to?

A

The alpha and gamma motor neurons throughout the length of the SC so influences mm throughout the body, facilitating the extensor mm and inhibiting the flexor mm

55
Q

Medial vestibulospinal tract (inputs & origin)

A

Originates in the lateral vestibular nucleus with inputs projecting mainly the utricle and saccule

56
Q

What is the tectospinal tract

A

A descending tract that coordinates head and eye movements

57
Q

Tectospinal tract pathway

A

Crude visual info projects to the superior colliculus and auditory to the inferior colliculus > CL and IPSI alpha motor neurons of the head/neck mm, oculomotor & throchlear nuclei & abducens nucleus

UM - Neuro Conditions (12 decks)

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