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MD2S3: Anatomy 203 > Descending Pathways > Flashcards

Descending Pathways Flashcards

1
Q

What are the categories of descending tracts?

A

Pyramidal tracts
Extra-pyramidal tracts

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2
Q

Names of pyramidal tracts

A

Lateral corticospinal
Anterior corticospinal
Corticonuclear

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3
Q

Names of extrapyramidal tracts

A

MEL VERT
Medial reticulospinal
Lateral reticulospinal
Vestibulospinal
Rubrospinal
Tectospinal

First three affect the alpha and gamma neurons in the anterior horn

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4
Q

Functions of extrapyramidal tracts

A

Autonomic control of musculature (muscle tone, balance, posture and locomotion)
Carry out gross voluntary movement to some extent in case of pyramidal tract damage

If gross voluntary movement is left under control of extrapyramidal tracts, muscle rigidity increases

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5
Q

What is the reticular formation?

A

Group of neurons in the core of the brain stem

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6
Q

Which structures do the reticular formation connect?

A

Spinal cord and thalamus to the cerebrum

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7
Q

Purpose of the reticular formation

A

Mediates sleep cycle

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8
Q

Medial Reticulospinal Tract
Function

A

Facilitates voluntary movements
Increases muscle tone
Stimulates α and γ neurons

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9
Q

Medial Reticulospinal Tract
Location

A

Anterior Funiculus

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10
Q

Medial Reticulospinal Tract
Origin

A

Pontine Reticular Formation

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11
Q

Medial Reticulospinal Tract
Crossed or Uncrossed

A

Uncrossed

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12
Q

Lateral Reticulospinal Tract
Function

A

Inhibits voluntary movements
Decreases muscle tone
Inhibits α and γ neurons

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13
Q

Lateral Reticulospinal Tract
Location

A

Lateral Funiculus

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14
Q

Lateral Reticulospinal Tract
Origin

A

Medullary Reticular Formation

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15
Q

Lateral Reticulospinal Tract
Crossed or Uncrossed

A

Crossed

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16
Q

Vestibulospinal Tract
Function

A

Control balance and posture by innervating anti-gravity muscles

Anti-gravity muscles include flexors of arm and extensors of the leg

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17
Q

Vestibulospinal Tract
Location

A

Anterior Funiculus

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18
Q

Vestibulospinal Tract
Origin

A

Lateral Vestibular Nucleus (pons)

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19
Q

Vestibulospinal Tract
Crossed or Uncrossed

A

Uncrossed

20
Q

Rubrospinal Tract
Function

A

Stimulates flexor muscles

21
Q

Rubrospinal Tract
Location

A

Lateral Funiculus

22
Q

Rubrospinal Tract
Origin

A

Red Nucleus (midbrain)

23
Q

Rubrospinal Tract
Crossed or Uncrossed

A

Crossed in midbrain

24
Q

Tectospinal Tract
Function

A

Coordinates in head movements in relation vision stimuli

25
Q

Tectospinal Tract
Location

A

Anterior Funiculus

26
Q

Tectospinal Tract
Origin

A

Superior colliculus (midbrain)

27
Q

Tectospinal Tract
Crossed or Uncrossed

A

Crossed in midbrain

28
Q

Lateral Corticospinal Tract
Functions

A

Skillful voluntary muscle movement of distal part of upper and lower limbs
Control voluntary movements of opposite half of body through anterior horn cells

29
Q

Lateral Corticospinal Tract
What percentage of fibers in pyramidal tract are formed from lateral corticospinal tract

A

80%

30
Q

Fill out

A
31
Q

Anterior Corticospinal Tract
Functions

A

Controls gross and postural movements of trunk and proximal musculature

32
Q

Anterior Corticospinal Tract
Found only in …

A

… cervical and thoracic segments

33
Q

Anterior Corticospinal Tract
What percentage of fibers in pyramidal tract are formed from anterior corticospinal tract

A

20%

34
Q

Anterior Corticospinal Tract
Where does the anterior corticospinal tract cross?

A

Does not cross at pyramid
Cross in spinal cord where they terminate

35
Q

Corticobulbar/Nuclear Tract
Origin

A

Primary Motor Area 4

36
Q

Corticobulbar/Nuclear Tract
Crossing occurs at …

A

… the brain stem at the level of motor nuclei of the cranial nerves

37
Q

Corticobulbar Tract
All the motor nuclei from the corticobulbar tract receive bilateral input except …

A

… cranial nerve 12 and upper part of 7th which have contralateral input

38
Q

Which motor nuclei of cranial nerves are in the midbrain

A

3rd and 4th (both pure motor)

Both mixed nerves

39
Q

Which motor nuclei of cranial nerves are in the pons?

A

5th, 7th (mixed)
6th (pure motor)

8th is in the pons but is sensory

40
Q

Which motor nuclei of the cranial nerves are in the medulla?

A

9th and 10th (mixed)
11th and 12th (pure motor)

41
Q

What are upper motor neuron pathways (UMN)?

A

From the cortex to their motor nerves

42
Q

What are lower motor neuron pathways (LMN)?

A

From UMN to effector

43
Q

What occurs when lesions form above the level of decussation?

A

Contralateral UMNL paralysis (loss of voluntary movements)

44
Q

What occurs when lesions form below the level of decussation

A

Ipsilateral UMNL paralysis

45
Q

What occurs in LMNL lesions?

A

Flaccid paralysis
Atrophy of muscles
Muscular fasciculations

46
Q

What is poliomyelitis?

A

Viral infection of motor neurons leading to paralysis

MD2S3: Anatomy 203 (31 decks)

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