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Neuroscience Final Exam > FE: Lecture 5: Local Segmental Control > Flashcards

FE: Lecture 5: Local Segmental Control Flashcards

1
Q

For an unconscious reflex control what types of nerves are used?

A

sensory in, motor out

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2
Q

Are these UMN?

A

no, b/c damage would not produce UMN syndrome

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3
Q

What happens when you step on a tack?

A

your L5/ S1 skin receptor goes to your LMN via adelta fibers in your spinal cord to dorsiflex foot

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4
Q

Does this AP go to your brain?

A

No, b/c in order to complete this action you do not have to think about it

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5
Q

Besides dorsiflexing you flex your hip, how does this happen?

A

the adelta goes to the LMN in your upper lumbar spinal cord through DLF and spinospinal tract

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6
Q

What is an example of a cranial withdrawal reflex?

A

corneal reflex CN 5 (sensory in) via interneuron to CN 7 (motor out)

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7
Q

What are the components of an intrinsic muscle fiber?

A

they have sensory mechanoreceptors and contractile fiber

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8
Q

What compromises the sensory mechanorecptors?

A

there type 1A bag fibers and type 2 chain fibers

these both detect stretch and change in muscle length

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9
Q

What comprises the contractile fibers?

A

these are the myofibrils that are innervated my gamma motor neurons

damage to these would not produce LMN syndrome

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10
Q

What is the main component of the extrinsic muscle fibers?

A

most of the bulk of myofibrils innervated by alpha motor neurons (LMN)

therefore damage would lead to flaccid paralysis

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11
Q

The intrinsic and extrinsic muscle fibers make up what?

A

a muscle spindle

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12
Q

What is the clinician’s view of the deep tendon reflex? For example what happens if the triceps is tapped and stretched?

A

receptor detects stretch and 1a fibers stimulated

they then synapse on triceps LMN and ascend DCML causing the triceps muscle to contract and inhibits biceps via interneurons

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13
Q

what is the Beer reflex?

A

if beer is randomly poured into your cup then your muscle is passively stretched but you need to correct this so beer doesn’t spill

LMN will correct this to contract right muscles to hold cup

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14
Q

What is a golgi tendon organ?

A

these are between muscle and tendons and are type 1B fibers

these are tendon stretch sensors and are important during active stretch

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15
Q

What does GTO during an active stretch?

A

due to negative feedback the GTO activates inhibitory intermotor neurons

which inhibits stretched muscles and excites antagonist muscle

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16
Q

What is muscle tone?

A

resistance to passive stretch

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17
Q

What are the two mechanisms of tone?

A
  1. active- due to spontaneous activity of LMN

2. passive- tense sacromeres, connective tissue stiffness

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18
Q

What happens if there is active muscle tone with LMN damage?

A

very low tone, loss of muscle innervation

also seen in myopathy

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19
Q

What happens if these is active muscle tone with UMN damage?

A

spasticity and rigidity, very high tone

due to loss of descending inhibition of segmental excitation

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20
Q

Describe the pathway of the corticospinal tract?

A

motor cortex through corona radiata then internal capsule posterior limb- cerebral peduncle- down to pyramids and cross at pyramidal decussation

21
Q

Where does LCST travel in the spinal cord?

A

crosses at pyramidal decussation and travels in lateral faniculus

control distal limb muscles and fine motor control

22
Q

Where does ACST travel in the spinal cord?

A

bilateral, crosses at spinal cord levels and goes down anterior fasiculus going to axial and proximal muscles for postural control

mainly at cervical but probably down whole spinal cord

23
Q

What happens in corticospinal UMN damage?

A

produces spastic paralysis- loss of volitional control and weakness

also increased tone and reflexes

24
Q

What specific reflexes are affected due to UMN CST damage?

A

withdrawal reflex increased

Babinski- in adults normal is toe flexion when bottom of foot, abnormal is extension

25
Q

What is the most important thing lost in UMN CST damage?

A

loss of fine motor control

26
Q

What is decerebrate UMN damage?

A

damage to brainstem in or near CST

contralateral extension of upper and lower limbs

27
Q

What is decoritcate UMN damage?

A

damage to motor cortex ( also corona radiata and internal capsule)

extension of LE, flexion of UE both contralateral to lesion

28
Q

What if UMN CSt is damaged at spinal cord?

A

ipsilateral UMN syndrome- decerebrate at and below lesion

29
Q

What if UMN CST damage at brainstem?

A
  1. pyramidal decussation level- bilateral UMN decerebrate all levels
  2. above decussation- CL UMN decerebrate syndrome all levels
30
Q

What if UMN CST at internal capsule?

A

CL UMN decorticate, all cord levels

31
Q

What if UMN CST damage at cerebral cortex?

A

CL decorticate UMN syndrome at damaged levels of homunculus

32
Q

What is the pathway of the corticobulbar tract?

A

motor cortex- corona radiata- internal capsule (genu)- cerebral peduncle- cross at pyramidal decussation

33
Q

Which two cranial nerves shows clear effects after an UMN ipsilateral lesion?

A

facial and hypoglossal

34
Q

What happens in UMN lesion of hypoglossal nerve?

A

CL tongue cannot pushes and deviates to weak side

crosses at hypoglossal nucleus

35
Q

What was old theory as to why Upper face was spared from UMN damage?

A

b/c upper CL face receives bilateral innervation from both left and right primary motor cortex

36
Q

What is the new theory?

A

the medial motor pathway- cingulate cortex goes to upper face LMN

there is a medial and lateral motor pathway for emotional and volitional control

37
Q

What is Duchane’s smile?

A

when you tell patients a joke they smile and both side work but when you ask them to smile only strong side works

38
Q

What is the medial VST?

A

medial, superior and inferior vestibular nucleus to bilateral cervical cord

function: stabilizes head and gaze

aka- descending MLF

39
Q

What is the lateral VST?

A

from lateral vestibular nucleus to ipsilateral entire cord

function- balance and posture

40
Q

What is the ascending MLF?

A

vestibular nuclei to CN 3, 4, 6

stabilizes eyes and gaze VOR reflex

41
Q

What is the tectospinal tract

A

superior and inferior colliculus= tectum, crosses immedeitly and goes to mostly cervical for controlling head and eye movements

function: important in orienting to visual and auditory stimuli, how does vision affect head and eye movements

optokinetic reflex

42
Q

What are reticular nuclei of the brainstem?

A

reticulum of neurons with long dendrites and axons

integrate many sensory and motor functions in the brainstem

43
Q

What are other major reticular nuclei to know?

A

periaqueductal grey, locus cerulus, ventral tegmental, raphe nuclei

44
Q

What are the functions of the reticular nuclei?

A

ascending projections to cortex for alertness, sleep

descending projections- reticulospinal projections to ventral horn neurons

45
Q

When the RST gets to ventral horn what are functions?

A

descending pain control and very important with gait control or pattern generators

they also inhibit contralateral extensor tone thus damage will lead to increased tone

46
Q

What is pathway of rubrospinal tract?

A

red nucleus in midbrain crosses in midbrain and goes to mostly cervical and thoracic region for upper limb control but in some species down to LE region

47
Q

What is theory about damage to rubrospinal tract?

A

above RN: decorticate rigidity elbow flexion

below- RN decerebrate rigidity elbow extension

48
Q

What is spinal shock syndrome?

A

if you damage T4 level then LMN syndrome at T4 level (intercostal muscles)

below lesion: no atrophy and decreased tone but then tone returns in a week and then increases

Neuroscience Final Exam (10 decks)

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