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Year 2 Term 2 C&M > Descending motor pathways > Flashcards

Flashcards in Descending motor pathways Deck (31)
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1
Q

Lower motor neuron lesions has what 5 clinical effects?

A

1) Muscle wasting (Atrophy as not stimulated)
2) Muscle weakness/ reduced power
3) Hypotonia - reduced resting muscle tone
4) Absent tendon reflexes
5) Fasciculation/ fibrillation

2
Q

What are the 3 roles of UMNs?

A

1) Influence LMN activity
2) Modify local reflex activity
3) Superimpose more complex patterns of movement

3
Q

Other than corticospinal/corticobulbar, what are the 3 other motor pathways?

A

1) Reticulospinal
2) Vestibulospinal
3) Rebrospinal

4
Q

Corticospinal pathway is mainly involved in what movement?

A

Voluntary fine precision movements

5
Q

What are the initial effects of selective damage to the corticospinal pathway? 2

A

1) Flaccid paralysis of contralateral limbs

2) Loss of tendon reflexes

6
Q

After several days following selective damage to the corticospinal tract and initial paralysis what occurs?

A

Motor function recovers but with hypertonia

7
Q

What are the 3 long terms effects of selective damage to the corticospinal pathway?

A

1) Spasticity
2) Hypereflexia
3) Permanent inability to carry out fine movements of hands and feet

8
Q

Corticobulbar fibres go from where to where?

A

Pre central gyrus to cranial nerve nuclei

9
Q

Cranial nerve motor nuclei are located where within the brainstem?

A

The floor of the 4th ventricle (pons)

10
Q

Corticobulbar fibres travel from the pre central gyrus to the cranial nerve nuclei via what?

A

Genu of the internal capsule

11
Q

Corticospinal fibres travel from where to where?

A

Pre central gyrus to the ventral grey horn of the spinal cord

12
Q

Are corticospinal and corticobulbar fibres UMNs or LMNs?

A

UMNs

13
Q

Are cranial nerves UMNs or LMNs?

A

LMNs

14
Q

Corticospinal fibres pass from pre central gyrus to brain stem via what?

A

Posterior limb of internal capsule

15
Q

What is the root of corticospinal fibres to the ventral grey horn?

A

From pre central gyrus via posterior limb of internal capsule
Descend through cerebral peduncles and ventral pons to pyramids
85% of fibres decussate at pyramids and descend through spinal cord in contralateral lateral corticospinal tract
15% of fibres descend in ipsilateral pyramids and ipsilateral anterior corticospinal tract through spinal cord

16
Q

The right pre central gyrus controls which side of the body?

A

The left

17
Q

Where do corticospinal neurones decussate?

A

85% within the medulla at decussation of pyramids

15% at level of exit through the spinal cord via the anterior white commissure

18
Q

Where do corticospinal neurones and LMNs synapse?

A

Contralateral ventral grey horn

19
Q

Where do corticospinal fibres descend within the spinal cord?

A

85% in contralateral lateral corticospinal tract

15% in ipsilateral anterior corticospinal tract

20
Q

The posterior limb of the internal capsule is somatotypically mapped, which lies most posterior, the arm of leg?

A

leg most posteriorly

Arm most anteriorly and trunk in the middle

21
Q

The cerebral peduncles are somatotypically mapped, which part of the body lies closest to the interpeduncular fossa and which furthest away?

A

Leg furthest away
Then trunk then arm
Then face closest to interpeduncular fossa

22
Q

The lateral corticospinal tract is somatotypically mapped, does the arm or leg lie most anterior?

A

arm lies most anterior

Leg lies most posterior

23
Q

How do LMNs leave the spinal cord?

A

Via the ventral grey horn as ventral rootlets to form spinal nerve

24
Q

Name the 8 cranial nerve motor nuclei?

A

1) CN3 - occulomotor
2) CN4 - trochlear
3) CN5 - trigeminal
4) CN6 - abducens
5) CN7 - facial
6) CN9 and 10 - glossopharyngeal and vagus
7) CN11 - accessory
8) CN12 - hypoglossal

25
Q

Corticobulbar fibres to all motor cranial nerve nuclei except hypoglossal and facial take what path?

A

From pre central gyrus via genu of internal capsule
Give some fibres to contralateral and some to ipsilateral nucleus
(MOST) CN NUCLEI ARE SERVED BILATERALLY

26
Q

Corticobulbar fibres synapse with LMNs where?

A

Motor cranial nerve nuclei

27
Q

How are hypoglossal motor nuclei served?

A

By contralateral corticobulbar fibres

28
Q

How does the facial motor nuclei differ to other cranial nerve nuclei?

A

Split into upper and lower part
Upper part sends fibres to muscles of upper face
Lower part sends fibres to muscles of lower face

29
Q

How is the upper part of facial motor nucleus served?

A

Served by bilateral corticobulbar fibres

So upper face is served bilaterally

30
Q

How is the lower part of facial motor nucleus served?

A

Served only by contralateral corticobulbar fibres

Lower face is served contralaterally

31
Q

How do LMN from the facial motor nucleus pass to the facial muscles?

A

Via the facial nerve
Passes out of skull via internal acoustic meatus
Passes through facial canal
Out of stylomastoid foramen
Branches into 5 branches within the substance of the parotid gland