Voluntary Motor Pathways

Question 1

Which motor pathways are involved in skilled movement?

Answer 1

Corticospinal

Corticobulbar

Question 2

Explain flexibility of strategy.

Answer 2

For knee jerk you are stimulating the same ligament every time causing the same contraction of the same muscle. For voluntary movement you can execute the movement using a variety of different limbs or muscles or sequence.

Question 3

Neurons from cortical areas make _________ (monosynaptic/ disynaptic/ polysynaptic) connections with the alpha and gamma motor neurons.

Answer 3

monosynaptic

Question 4

It is through __________neurons that signals will go to the spinal cord and brainstem motor nuclei

Answer 4

upper motor

Question 5

The LMN are something called the ___________ pathways because no matter where the signal comes from all of that info has to go to LMN and the information has to converge on this final common pathw

Answer 5

final common

Question 6

Damage of the spinal cord & lesion of motor pathways below the origin of the brachial plexus (C5-T1) and above S4 results in __________.

Answer 6

paraplegia.

Question 7

Damage of the spinal cord at the origin of the brachial plexus results in ________.

Answer 7

quadreplegia.

Question 8

Damage of the spinal cord at the origin of the _________ or above results in asphyxiation and death (without medical intervention).

Answer 8

phrenic nerve

Question 9

This area is th emost important in initiating skilled, controlled motor movements

Answer 9

Primary motor cortex

Question 10

What are the two components of the premotor region?

Answer 10

• Premotor cortex
• Supplementary cortex

Question 11

The supplementary motor cortex is motor area _______

Answer 11

2

*this is apart of Broadman area 6

Question 12

•When we talk about area 4 and 6 (motor cortex), it lacks layer ______, which is the inner granular layer

Answer 12

4

*Or this layer is extremely small

Question 13

Because the primary cortex is interested in movement and not analyzing sensory information it lacks a well defined inner granular cortex, so it is referred to sometimes as __________.

Answer 13

agranular cortex

Question 14

What areas 4 and 6 do have is a well defined layer______, which has lots of pyramidal cells; these are projection neurons and area 4 in particular has giant pyramidal cells.

Answer 14

5

Question 15

The cell bodies of the corticospinal tract are found in layer __.

Answer 15

5

Question 16

In the primary motor cortex there are very large pyramidal cells called ________cells and they contribute 30,000 of the 1 million axons

Answer 16

betz

Question 17

There are pyramidal cells in layers 5 and 6 of the cortex. However, the pyramidal cells are different in layer 6. In what way(s)?

Answer 17

• They do NOT form the corticospinal tract
• They have a single apical dendrite that ascends up to the cortical surface and synaptic input from the upper 4 layers make synaptic contact with this apical dendrite and then a single axon descends the spinal cord to terminate on motor neurons and interneurons.

Question 18

What are the contributions to the corticospinal tract?

Answer 18

• 1/2 from primary motor cortex
• Most of the other contributions are from the supplementary motor cortex
• Some contributions are from the parietal cortex and the somatosensory cortex

Question 19

What is the evidence that the precentral gyrus is the

‘Primary Motor Cortex?’

Answer 19

When you shock the precentral gyrus you can produce a single twitch of a single muscle, particularly in the hands; sometimes you will get contractions of other smaller muscles in the hand but often times you can isolate the direct connection between the cortex and muscles of the hand and forearm and other parts of the body. This can’t be done in any other parts of the brain

Question 20

What are the characteristics of movements induced by electrical stimulation to the motor cortex?

Answer 20

1. an individual (or a few) muscle
2. the lowest threshold
3. short latency

*When you measure the amount of electricity it takes to stimulate a muscle, the threshold for stimulating the motor cortex is the lowest

Question 21

The more synapses in a pathway, the ________ (longer/shorter) the latency is between stimulus and response

Answer 21

longer

Question 22

When they study the motor cortex, they have developed the motor map which is called the _________; specific areas of the motor cortex control specific parts of the body.

Answer 22

homunculus

Question 23

The ________________artery supplies the cortical region supplying the lower limb.

Answer 23

anterior cerebral

Question 24

The ____________artery supplies the region of the hand and face.

Answer 24

middle cerebral

Question 25

Lesion of which artery can cause **monoplegia\>**

Answer 25

Anterior cerebral artery Middle cerebral artery

Question 26

Is there spike activity in the extensors when the corticospinal tract is stimulated?

Answer 26

No. \*Just during flexion. there is also spike activity prior to the contraction when flexing.

Question 27

What happened when area 6 was stimulated with activity? Do you get movement?

Answer 27

* You stimulate Brodmann’s area 6 you can get movements but it takes more electricity than area 4 * If you stimulate supplementary motor area, instead of getting discrete movements you get **complex movement** like opening and closing the hands, usually bilateral, and postural movements **NOTE:** If you lesion area 6 you get apraxia and the patient will have difficulty carrying out complex , purposeful movements

Question 28

What is ideomotor apraxia?

Answer 28

If you ask the patient to mimic/pretend they are combing the hair or touch the nose they can’t do it, BUT if the nose itches they can do it or if they need to push the hair back out of the face they can do that without thinking about it

Question 29

Is the primary motor cortex involved in "rehearsing" activity?

Answer 29

No, only the supplementary motor cortex

Question 30

What is the function of the supplementary motor cortex?

Answer 30

* Plans a strategy for movement requiring sequences of muscles contractions or a planned strategy * Important in programming motor sequences and in coordinating bilateral movements and postural responses

Question 31

The supplementary motor cortex controls which muscles?

Answer 31

a**. postural muscles** through the corticospinal tract. b. **distal muscles** (such as in the hand) through area 4

Question 32

Lateral premotor cortex controls \_\_\_\_\_\_\_\_\_\_\_\_.

Answer 32

proximal limb movements that project or orient the arm to targets

Question 33

What is the function of the lateral premotor cortex?

Answer 33

* Plays a role in interjoint coordination * Controls **proximal** limb movements that project or orient the arm to targets Ex: If you want to paint something in space the first thing you have to do is get the arm in right position; this is largely controlled by the lateral premotor cortex.

Question 34

What are the three complex movements required for voluntary movement? What parts are the cortex are involved in each movement?

Answer 34

1. **Identification of target** - posterior parietal cortex (5 & 7) 2. **Plan movement** – supplementary motor cortex (6) 3. **Execute movement** – primary motor cortex (4)

Question 35

When looking at complex movements the areas of the \_\_\_\_\_\_\_\_\_\_are involved in visually guided behavior; it is important in identifying a target that we want to move toward.

Answer 35

parietal cortex

Question 36

The plan of the movement will be done mostly by __________ cortex.

Answer 36

supplementary motor

Question 37

The execution of the fine movement done by the hands or feet is done by the \_\_\_\_\_\_\_\_\_\_\_cortex

Answer 37

primary motor

Question 38

The supplementary motor cortex first organizes the \_\_\_\_\_\_\_\_\_\_\_\_adjustments and then makes possible the desired movement.

Answer 38

postural \*•Postural adjustments are required to happen in concert with fine movements

Question 39

Corticospinal fibers pass through the _________ limb of the internal capsule.

Answer 39

posterior

Question 40

The corticobulbar fibers controlling the motor nuclei of the brainstem are in the \_\_\_\_\_\_\_.

Answer 40

genu

Question 41

Usually the \_\_\_\_\_\_\_\_\_is not affected by a lesion of the posterior limb of the IC.

Answer 41

Face

Question 42

Capsular lesions are commmonly due to obstuctruction or hemorrhage of which arteries?

Answer 42

a) deep branches of the middle cerebral b) anterior choroidal artery * Most distal part of the ICA

Question 43

Label

Answer 43

**NOTE:** The corticospinal fibers pass through the brainstem after leaving the internal capsule. The fibers go from the cortex to the pons then they cross in the medulla and form the pyramids.

Question 44

On which level of the brainstem are the cerebral peduncles found?

Answer 44

Midbrain

Question 45

Which nerve, tract, and central nuclei are affected in medial midbrain syndrome?

Answer 45

**_Nerve_** * Oculomotor **_Tract_** * Corticospinal * Corticobulbar * Corticopontine **_Central Nuclei_** * Substantia nigra * Red nucleus (cerebellothalamic fibers)

Question 46

Corticospinal fibers separate into fascicles in the \_\_\_\_\_\_\_\_\_pons

Answer 46

ventral

Question 47

Medial midbrain syndrome is caused by an occlusion of which artery?

Answer 47

P1 of PCA

Question 48

Weber's syndrome

Answer 48

Ipsilateral oculomotor palsy + Contralateral hemiparesis/ hemiplegia

Question 49

Claude's syndrome

Answer 49

Unilateral infarction of the **red nucleus and cerebral peduncle**, affecting several structures in the midbrain leading to: * **contralateral ataxia** * **contralateral hemiparesis** * **contralateral hemiplegia** of lower facial muscles, tongue, and shoulder * **ipsilateral oculomotor nerve palsy** with a drooping eyelid and fixed wide pupil pointed down and out; probable diplopia

Question 50

Benedikt's syndrome

Answer 50

* Results from occlusion of the posterior cerebral artery or paramedian penetrating branches of the basilar artery * Results from damage to tegmentum

Question 51

Differentiate Weber's syndrome from Benedick's syndrome

Answer 51

**_Weber_** * Occlusion of P1 of PCA * Hemiplegia **_Benedick's_** * Occlusion of paramedian branches of basilar artery * Hemiataxia

Question 52

Differentiate Claude's syndrome from Benedick's syndrome

Answer 52

**_Claude_** * Occlusion of P1 of PCA * more predominant tremor and choreoathetotic movements **_Bendick's_** * Occlusion of the paramedian branches of basilar artery * More characteristic of ataxia

Question 53

Artery of Percheron

Answer 53

**Rare** anatomic variation in the brain vascularization in which a single arterial trunk arises from the **posterior cerebral artery (PCA)** to supply both sides of brain structures; the **thalamus and midbrain.**

Question 54

What is the clinical significance of the artery of percheron?

Answer 54

bizarre disturbance such as sleep from which the patient cannot be awakened

Question 55

Medial medullary syndrome is caused by occlusion of which artery?

Answer 55

Anterior spinal artery Medial branches of vertebral artery

Question 56

Which tracts and nuclei are affected by medial medullary syndrome?

Answer 56

**_Nuclei_** * CN XII **_Tracts_** * Corticospinal * Medial leminscus * MLF

Question 57

90% of pyramidal fibers decussate (cross) at the junction of the _________ and \_\_\_\_\_\_\_\_\_\_.

Answer 57

medulla and spinal cord

Question 58

•The pyramids are the fibers crossing to the other side and they will form the lateral corticospinal tract * If there is lesion in the middle of the decussation the symptoms will be __________ because the fibers are crossing in both directions * If the lesion was in the pyramids the symptoms would be \_\_\_\_\_\_\_\_\_.

Answer 58

bilateral;contralateral

Question 59

The lateral corticospinal tract innervates\_\_\_\_\_\_\_\_\_motor nuclei of the ventral horn

Answer 59

lateral

Question 60

The ventral corticospinal tract innervates \_\_\_\_\_\_\_\_\_motor nuclei of the ventral horn

Answer 60

medial **\*Note**: some axons of the ventral tract cross at the segmental level; therefore, the projection is **bilateral**

Question 61

Lateral motor nuclei innervate\_\_\_\_\_\_\_\_\_\_\_\_ Medial motor nuclei innervate \_\_\_\_\_\_\_\_\_\_\_

Answer 61

limb musculature axial musculature

Question 62

Corticospinal axons synapse on 4 different types of neurons. What are they?

Answer 62

Corticospinal axons synapse on: 1. alpha motor neurons\* 2. gamma motor neurons\* (to muscle spindles) 3. intrasegmental interneurons (that project within the segment) 4. intersegmental (propriospinal) interneurons (that ascend & descend to other segmental levels)

Question 63

What characteristics in humans allow for better dexterity?

Answer 63

Direct connections from the cortex to lower motor neurons. \*You still have indirect pathway through interneurons but to do learned skilled movements you have the direct connections between cortex and lower motor neuron that lower vertebrates don’t have

Question 64

Corticospinal tract has a: 1) \_\_\_\_\_\_\_\_\_\_\_\_ effect on flexor motor neurons 2) \_\_\_\_\_\_\_\_\_\_\_\_\_ effect on extensor motor neurons

Answer 64

facilitatory inhibitory

Question 65

Explain the relationship between the corticospinal tract and the Babinski reflex.

Answer 65

In babies, the Babinski reflex induces extension and fanning of toes. Once the corticospinal tract grows in, the Babinski reflex is inhibited and the same stimulus will produce flexion instead

Question 66

Activity of ___________ Motor Neurons Is Modulated by the Corticospinal Tract

Answer 66

Gamma

Question 67

Very shortly after injury to the brain or spinal cord, upper motor signs may be lacking, and, therefore, may even be falsely interpreted as lower motor neuron signs. This transient state is known as \_\_\_\_\_\_\_\_\_\_\_.

Answer 67

‘cerebral’ or ‘spinal shock’

Question 68

Spasticity is greater in ________ of the arms but __________ of the legs.

Answer 68

flexors; extensors

Question 69

Lesions anywhere along the corticospinal tract produce __________ motor neuron signs

Answer 69

upper

Question 70

The difference between the corticobulbar and corticospinal is that corticobulbar, for most clinical purposes, is \_\_\_\_\_\_\_\_\_\_\_.

Answer 70

bilateral **EXCEPTION:** Projections to the lower half of the face and the hypoglossal nerve

Question 71

Pseudobulbar palsy

Answer 71

pseudobulbar palsy \*Due to bilaterality of the cortibobulbar tract