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Flashcards in Movement pathways and centre Deck (54):
1

What are lower motor neurons (LMNs) ?

neurons that originate from the brain stem and spinal cord

2

What are the components to the lower motor neuron (LMN)?

1. spinal nerve
2. ventral root
3. dorsal root ganglion
4. dorsal root
5. dorsal grey horn
6. ventral grey horn

3

What are lower motor neuron lesions due to?

1. peripheral nerve injury - crush or poliomyelitis
2. poliomyelitis

4

What do lower motor neuron lesions lead to?

1. muscle wasting
2. muscle weakness/ reduced power
3. hypotonia
4. absent tendon reflexes
5. fasciculations/ fibrillation

5

What are fasiculations?

small uncontrollable localised contractions

6

What is an example of a descending mortor pathway?

upper motor neurons (UMNs)

7

What 2 types of descending motor pathways are there?

1. corticospinal - cortex to spine - spinal nerves
2. corticobulbar - cortex to brainstem - cranial nerves

8

What does the descending motor pathways/ upper motor neurons do?

1. influence LMN activity
2. modify local reflex activity
3. superimpose more complex patterns of movement

9

How many important descending pathways are there and what are they named after?

4

named after origin

10

What is the typical route for descending patwhays/ upper motor neurons?

1. cerebral cortex
2. precentral gyrus
3. internal capsule
4. brainstem/spinal cord

11

Do all descending pathways work separately or together?

together

12

What are the descending pathways often referred to as?

pyramidal system

13

What happens initially if there is damage to the corticospinal tract only?

1. flaccid paralysis of opposite limbs
2. loss of tendon reflexes

14

What happens after several days to a week if there is damage in the corticospinal tract only?

1. motor function recovers

2. but there is hypertonia

15

What happens in the long term if there is damage to the corticospinal tract?

1. spasticity
2. hyperreflexia - increased reflexes
3. left with pernamanet inability to carry out fine movements of hands and feet

16

What do other pathways seem to do if there is damage to the corticospinal tract only?

appear to take over most corticospinal functions

17

What type of homunculus do you have?

1. somatosensory
2. motor homunculus

18

Where is the somatosensory homunculus?

in the post-central gyrus

19

Where is the motor homunculus?

in the pre-central gyrus

20

What is the order of the motor homunculus in the pre-cnetral gyrus medial to lateral?

1. knee
2. hip
3. trunk
4. shoulder
5. arm
6. elbow
7. wrist
8. hand
9. fingers
10. thumb
11. neck
12. brow
13. eye
14. face
15. jaw
16. tongue
17. pharynx
18. larynx

21

What is the order of the somatosensory homunculus in the post-central gyrus medial to lateral?

1. leg
2. hip
3. trunk
4. arm
5. elbow
6. forearm
7. hand
8. fingers
9. thumb
10. eye
11. nose
12. face
13. lips
14. teeth
15. gums
16. jaw
17. tongue
18. pharynx
19. abdomen

22

Where does the descending pathway (descending corticospinal/bulbar fibres) or upper motor neuron travel?

1. from pre central gyrus to internal capsule

23

What is the internal capsule?

deep bundle of white matter between the deep nuclei

24

What is the structure of the internal capsule?

1. anterior limb of internal capsule
2. lower limb of internal capsule
3. genu

25

Where do descending fibres for the body go?

posterior limb of the internal capsule

26

Where do descending fibres fro the face and muscles of the head go?

genu

27

What is the structure of the brainstem?

1. cerebral peduncle
2. basal pons
3. pyramids
4. olives

midbrain
pons
medulla

28

How does the descending pathway travel from internal capsule to spinal cord?

in the brainstem from cerebral peducnle to basal pons to pyramids and to contralateral spinal cord

29

How does the corticospinal pathway travel from cortex to spinal cord?

1. pre-central gyrus in cortex
2. inetrnal capsule
3. basis peduncles
4. pyramid
5. pyramidal decusstaion
6. lateral corticospinal tract

30

In terms of the decussation of pyramids what percentage of fibres cross and enter the lateral corticospinal tract?

85% fibres cross

31

In terms of the corticospinal tract what percentage of UMNs descend the cord contra laterally?

85%

32

In terms of the corticospinal tract what percentage of UMNs descend the cord ipsilaterally?

15% remain ipsilateral in anterior/ventral CST

then cross at appropriate spinal cord level

33

Where do the UMNs contact cell bodies of LMNs?

in contralateral ventral grey horn

34

What do second order neurons of LMNs do in the corticospinal tract?

leave spinal cord as ventral rootlets to form spinal nerve

35

What is retained throughout the cord?

somatotopic representation

36

Where does the corticospinal tract leave and descend to?

leave pre-central gyrus

descend - posterior limb of internal capsule

then goes to cerebral peduncle of midbrain, ventral ons and pyramids of the medulla

37

How does the corticospinal tract extend to skeletal/straiated muscle?

via segemental spinal nerve

38

Where does the corticobulbar pathway influence the LMNs?

in cranial nerve motor nuclei

39

Where do the fibres of the corticobulbar pathway originate from?

laterally within the pre-central gyrus

40

Is the innervation of LMNs bilateral or unilateral?

bilateral - corticospinal tract on left supplies muscles on the left and right and vice versa

41

Where does the facial nerve nuclei receive UMNs from?

from a specific motor area of the pre-central gyrus

42

Wheer does the LMNs leave and pass through and exit?

leave from the facial nerve nuclei

pas through substance of the pons

exit brainstem at the cerebellopontine angle

43

Where does the facial nucleus originate from?

floor of the 4th ventricle

44

What are the 5 divisions of the facial nerve?

To Zanzibar By Motor Car

45

NOTE

LEARN THE CORTICOBULBAR INPUT TO CRANILA NERVE MOTOR NUCLEI

46

NOTE

LEARN TEH CORTICOBULBAR INPUT TO FACIAL MOTOR NUCELI

47

If there is right corticobulbar damage what is affected?

upper motor neuron type facial weakness

left facial weakness from below the eye to the chin

48

If there is left facial nerve damage what is affected?

lower motor neuron type facial weakness

whole left side of the face

49

What is another word fro unilateral damage to corticobulbar fibres?

supranuclear lesion

50

What happens in unilateral damage to corticobulbar fibres/ supra nuclear lesion?

it deprives the lower half of the opposite facla motor nucleus of corticobulbar input

results in paralysis of the whole half of the face on the opposite side to the lesion

51

What does paralysis of the whole of one side of the face indicate?

damage to the facial nerve itself

52

How do you differentiate between a supra nuclear and facial nerve lesion?

look up

53

What are features of upper motor nerve lesions?

contralateral lower quadrant weakness

angle of mouth

opposite side

54

What are features of the lower motor nerve lesion?

ipsilateral orbicularis oculi muscles and facila muscles involved

half of face - unable to close eyes

weakness of angle of the mouth

cannot elevate eyebrows

same side