Descending Pathways

Question 1

What are the categories of descending tracts?

Answer 1

Pyramidal tracts
Extra-pyramidal tracts

Question 2

Names of pyramidal tracts

Answer 2

Lateral corticospinal
Anterior corticospinal
Corticonuclear

Question 3

Names of extrapyramidal tracts

Answer 3

MEL VERT
Medial reticulospinal
Lateral reticulospinal
Vestibulospinal
Rubrospinal
Tectospinal

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

Question 4

Functions of extrapyramidal tracts

Answer 4

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

Question 5

What is the reticular formation?

Answer 5

Group of neurons in the core of the brain stem

Question 6

Which structures do the reticular formation connect?

Answer 6

Spinal cord and thalamus to the cerebrum

Question 7

Purpose of the reticular formation

Answer 7

Mediates sleep cycle

Question 8

Medial Reticulospinal Tract
Function

Answer 8

Facilitates voluntary movements
Increases muscle tone
Stimulates α and γ neurons

Question 9

Medial Reticulospinal Tract
Location

Answer 9

Anterior Funiculus

Question 10

Medial Reticulospinal Tract
Origin

Answer 10

Pontine Reticular Formation

Question 11

Medial Reticulospinal Tract
Crossed or Uncrossed

Answer 11

Uncrossed

Question 12

Lateral Reticulospinal Tract
Function

Answer 12

Inhibits voluntary movements
Decreases muscle tone
Inhibits α and γ neurons

Question 13

Lateral Reticulospinal Tract
Location

Answer 13

Lateral Funiculus

Question 14

Lateral Reticulospinal Tract
Origin

Answer 14

Medullary Reticular Formation

Question 15

Lateral Reticulospinal Tract
Crossed or Uncrossed

Answer 15

Crossed

Question 16

Vestibulospinal Tract
Function

Answer 16

Control balance and posture by innervating anti-gravity muscles

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

Question 17

Vestibulospinal Tract
Location

Answer 17

Anterior Funiculus

Question 18

Vestibulospinal Tract
Origin

Answer 18

Lateral Vestibular Nucleus (pons)

Question 19

Vestibulospinal Tract
Crossed or Uncrossed

Answer 19

Uncrossed

Question 20

Rubrospinal Tract
Function

Answer 20

Stimulates flexor muscles

Question 21

Rubrospinal Tract
Location

Answer 21

Lateral Funiculus

Question 22

Rubrospinal Tract
Origin

Answer 22

Red Nucleus (midbrain)

Question 23

Rubrospinal Tract
Crossed or Uncrossed

Answer 23

Crossed in midbrain

Question 24

Tectospinal Tract
Function

Answer 24

Coordinates in head movements in relation vision stimuli

Question 25

**Tectospinal Tract** Location

Answer 25

Anterior Funiculus

Question 26

**Tectospinal Tract** Origin

Answer 26

Superior colliculus (midbrain)

Question 27

**Tectospinal Tract** Crossed or Uncrossed

Answer 27

Crossed in midbrain

Question 28

**Lateral Corticospinal Tract** Functions

Answer 28

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

Question 29

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

Answer 29

80%

Question 30

Fill out

Answer 30

Question 31

**Anterior Corticospinal Tract** Functions

Answer 31

Controls gross and postural movements of trunk and proximal musculature

Question 32

**Anterior Corticospinal Tract** Found only in ...

Answer 32

... cervical and thoracic segments

Question 33

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

Answer 33

20%

Question 34

**Anterior Corticospinal Tract** Where does the anterior corticospinal tract cross?

Answer 34

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

Question 35

**Corticobulbar/Nuclear Tract** Origin

Answer 35

Primary Motor Area 4

Question 36

**Corticobulbar/Nuclear Tract** Crossing occurs at ...

Answer 36

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

Question 37

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

Answer 37

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

Question 38

Which motor nuclei of cranial nerves are in the midbrain

Answer 38

3rd and 4th (both pure motor) ## Footnote Both mixed nerves

Question 39

Which motor nuclei of cranial nerves are in the pons?

Answer 39

5th, 7th (mixed) 6th (pure motor) ## Footnote 8th is in the pons but is sensory

Question 40

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

Answer 40

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

Question 41

What are upper motor neuron pathways (UMN)?

Answer 41

From the cortex to their motor nerves

Question 42

What are lower motor neuron pathways (LMN)?

Answer 42

From UMN to effector

Question 43

What occurs when lesions form above the level of decussation?

Answer 43

Contralateral UMNL paralysis (loss of voluntary movements)

Question 44

What occurs when lesions form below the level of decussation

Answer 44

Ipsilateral UMNL paralysis

Question 45

What occurs in LMNL lesions?

Answer 45

Flaccid paralysis Atrophy of muscles Muscular fasciculations

Question 46

What is poliomyelitis?

Answer 46

Viral infection of motor neurons leading to paralysis