Spinal cords: descending tracts

Question 1

What lobe of the brain are the motor areas a part of?

Answer 1

Frontal

Question 2

Where does the primary motor cortex sit?

Answer 2

Pre-central gyrus

Broadmann Area 4

Question 3

What input does the primary motor cortex receive?

Answer 3

Pre-motor cortex and supplementary motor area (Broadmann Area 6)
Cerebellum (via the ventrolateral nucleus of the thalamus)
Somatosensory cortex

Question 4

What is the output of the primary motor cortex?

Answer 4

Origin of 80-90% of upper motor neurons of the corticospinal tract

Question 5

What would injury to the primary motor cortex result in?

Answer 5

Contralateral paralysis and paresis (weakness)

Question 6

Where does the supplementary motor area receive input from?

Answer 6

Basal ganglia

Pre-frontal cortex

Question 7

What is the function of the supplementary motor area?

Answer 7

Planning motor tasks

Activated by internally generated movement intention from the pre-frontal cortex

Question 8

What would injury to the supplementary motor area result in?

Answer 8

Unilateral akinesia on the contralateral side of the body

Question 9

What is a motor unit?

Answer 9

A lower motor neuron + the extrafusal muscle fibres it innervates

Question 10

What is the difference in number of motor units between unrefined powerful muscles and muscles with fine control?

Answer 10

Large number of muscle fibres per motor unit in unrefined powerful muscles (1000+)
Few muscle fibres per motor unit in muscles with fine control (~10)

Question 11

What is a myotome?

Answer 11

Muscle fibres innervated by a single spinal nerve

Question 12

What do alpha lower motor neurons innervate?

Answer 12

Motor units of extrafusal fibres
Initiates contraction of muscle
[Large myelinated axons]

Question 13

What do gamma motor neurons innervate?

Answer 13

Intrafusal fibres of muscle spindles

[Smaller diameter axons]

Question 14

Where are intrafusal fibres found and and what do they do?

Answer 14

Inside a connective tissue capsule in muscle spindles

Keep muscle spindle under load during muscle contraction and detects change in muscle length

Question 15

What is monoplegia?

Answer 15

Paralysis of one limb

Question 16

What is hemiplegia?

Answer 16

Paralysis of arm and leg on ipsilateral side of body

Question 17

What is diplegia?

Answer 17

Paralysis of both arms

Question 18

What is paraplegia?

Answer 18

Paralysis of both legs

Question 19

What is quadraplegia?

Answer 19

Paralysis of all limbs

Question 20

What part of the spinal cord do the posterior spinal arteries supply?

Answer 20

Posterior 1/3 of spinal cord

Question 21

What is Amytrophic Lateral Sclerosis (Lou Gehrig Disease)?

Answer 21

Degeneration of the corticospinal tracts and ventral horn of the spinal cord

Question 22

What symptoms can be seen in patients with ALS?

Answer 22

Fasciculations 
Spasticity/ cramps 
Weakness
Dysarthria 
Dysphagia 
Dyspnoea 
[LMN and UMN lesion symptoms seen - often starting in limbs before spreading elsewhere]

Question 23

What do the corticospinal tracts control?

Answer 23

Speed, direction and agility of movements

Rapid, skilled, fine movement

Question 24

Which corticospinal tract contains the majority of neurons?

Answer 24

Lateral CST = 80-90%

Ventral CST = 10-20%

Question 25

Where do UMNs in the corticospinal tracts synapse with LMNs?

Answer 25

Ventral grey horn at level of exit from the spinal cord

Question 26

Where can upper motor lesions occur?

Answer 26

Cortex
Internal capsule 
Corona radiata 
Descending tracts 
Brainstem 
Spinal cord

Question 27

Where can lower motor lesions occur?

Answer 27

Spinal cord
Spinal nerve
Cauda equina
Peripheral nerve damage

Question 28

What are the symptoms of an upper motor neuron lesions?

Answer 28

Hyper-reflexia
Extensor Plantar reflex (Babinski sign)
No muscle wasting
Spastic paralysis

Question 29

What are the symptoms of a lower motor neuron lesion?

Answer 29

Fasciculations
Muscle wasting
Flaccid paralysis
Hypo-reflexia

Question 30

What is Brown-Sequard syndrome?

Answer 30

Hemisection of the spinal cord resulting in ipsilateral hemiplegia and contralateral hemianaesthesia

Question 31

What is the major motor pathway to the face?

Answer 31

Cortciobulbar tract

Question 32

What does the vestibulospinal tract control?

Answer 32

Extensor muscle tone (anti-gravity muscles)