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Anatomy term 2 > Movement pathways and centre > Flashcards

Movement pathways and centre Flashcards

1
Q

What are lower motor neurons (LMNs) ?

A

neurons that originate from the brain stem and spinal cord

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2
Q

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

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

What are lower motor neuron lesions due to?

A
  1. peripheral nerve injury - crush or poliomyelitis

2. poliomyelitis

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4
Q

What do lower motor neuron lesions lead to?

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

What are fasiculations?

A

small uncontrollable localised contractions

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6
Q

What is an example of a descending mortor pathway?

A

upper motor neurons (UMNs)

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7
Q

What 2 types of descending motor pathways are there?

A
  1. corticospinal - cortex to spine - spinal nerves

2. corticobulbar - cortex to brainstem - cranial nerves

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8
Q

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

A
  1. influence LMN activity
  2. modify local reflex activity
  3. superimpose more complex patterns of movement
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9
Q

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

A

4

named after origin

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10
Q

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

A
  1. cerebral cortex
  2. precentral gyrus
  3. internal capsule
  4. brainstem/spinal cord
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11
Q

Do all descending pathways work separately or together?

A

together

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12
Q

What are the descending pathways often referred to as?

A

pyramidal system

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13
Q

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

A
  1. flaccid paralysis of opposite limbs

2. loss of tendon reflexes

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14
Q

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

A
  1. motor function recovers

2. but there is hypertonia

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15
Q

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

A
  1. spasticity
  2. hyperreflexia - increased reflexes
  3. left with pernamanet inability to carry out fine movements of hands and feet
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16
Q

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

A

appear to take over most corticospinal functions

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17
Q

What type of homunculus do you have?

A
  1. somatosensory

2. motor homunculus

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18
Q

Where is the somatosensory homunculus?

A

in the post-central gyrus

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19
Q

Where is the motor homunculus?

A

in the pre-central gyrus

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20
Q

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

A
  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
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21
Q

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

A
  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
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22
Q

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

A
  1. from pre central gyrus to internal capsule
23
Q

What is the internal capsule?

A

deep bundle of white matter between the deep nuclei

24
Q

What is the structure of the internal capsule?

A
  1. anterior limb of internal capsule
  2. lower limb of internal capsule
  3. genu
25
Q

Where do descending fibres for the body go?

A

posterior limb of the internal capsule

26
Q

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

A

genu

27
Q

What is the structure of the brainstem?

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

midbrain
pons
medulla

28
Q

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

A

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

29
Q

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

A
  1. pre-central gyrus in cortex
  2. inetrnal capsule
  3. basis peduncles
  4. pyramid
  5. pyramidal decusstaion
  6. lateral corticospinal tract
30
Q

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

A

85% fibres cross

31
Q

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

A

85%

32
Q

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

A

15% remain ipsilateral in anterior/ventral CST

then cross at appropriate spinal cord level

33
Q

Where do the UMNs contact cell bodies of LMNs?

A

in contralateral ventral grey horn

34
Q

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

A

leave spinal cord as ventral rootlets to form spinal nerve

35
Q

What is retained throughout the cord?

A

somatotopic representation

36
Q

Where does the corticospinal tract leave and descend to?

A

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
Q

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

A

via segemental spinal nerve

38
Q

Where does the corticobulbar pathway influence the LMNs?

A

in cranial nerve motor nuclei

39
Q

Where do the fibres of the corticobulbar pathway originate from?

A

laterally within the pre-central gyrus

40
Q

Is the innervation of LMNs bilateral or unilateral?

A

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

41
Q

Where does the facial nerve nuclei receive UMNs from?

A

from a specific motor area of the pre-central gyrus

42
Q

Wheer does the LMNs leave and pass through and exit?

A

leave from the facial nerve nuclei

pas through substance of the pons

exit brainstem at the cerebellopontine angle

43
Q

Where does the facial nucleus originate from?

A

floor of the 4th ventricle

44
Q

What are the 5 divisions of the facial nerve?

A

To Zanzibar By Motor Car

45
Q

NOTE

A

LEARN THE CORTICOBULBAR INPUT TO CRANILA NERVE MOTOR NUCLEI

46
Q

NOTE

A

LEARN TEH CORTICOBULBAR INPUT TO FACIAL MOTOR NUCELI

47
Q

If there is right corticobulbar damage what is affected?

A

upper motor neuron type facial weakness

left facial weakness from below the eye to the chin

48
Q

If there is left facial nerve damage what is affected?

A

lower motor neuron type facial weakness

whole left side of the face

49
Q

What is another word fro unilateral damage to corticobulbar fibres?

A

supranuclear lesion

50
Q

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

A

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
Q

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

A

damage to the facial nerve itself

52
Q

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

A

look up

53
Q

What are features of upper motor nerve lesions?

A

contralateral lower quadrant weakness

angle of mouth

opposite side

54
Q

What are features of the lower motor nerve lesion?

A

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

Anatomy term 2 (25 decks)

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