Lecture 6: Lower Motor Neurons Flashcards

1
Q

Where are alpha lower motor neurons located in the spinal cord?

A

Ventral horn; Proximal muscles more medial, distal are lateral, flexors are more dorsal to extensors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How are small and large motor neurons matched to muscles?

A

Small- 1 type muscles fibers that cause slow slowly-fatiguing constractions
Large- IIb fibers that cause large fast quickly fatiguing contractions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Lower motor neuron signs

A

No reflexes, flaccid paralysis, hypotonia, fasciculations, muscle atrophy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Upper motor neuron signs

A

Hyperreflexia, spastic paralysis, Hypertonia, + Babinski sign

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Corticospinal pathway

A

Motor cortex to spinal cord tract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Ventromedial pathways

A

Reticulo, tecto, and vestibulospinal pathways that are involved with proximal/axial muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Lateral motor pathways

A

Corticospinal and rubrospinal; fine movements in distal muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What cortex layer do corticospinal fibers arise from?

A

5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where do corticospinal neurons cross the midline?

A

Pyramidal decussation in lower medulla

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where do rubrospinal neurons cross the midline?

A

Right away in midbrain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Lesion in corticospinal path

A

In spinal cord- ipsilateral motor deficit

Above spinal cord- contralateral motor deficit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Lesion in rubrospinal path

A

Contralateral motor deficit no matter where along the length the lesion is

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Vestibulospinal path

A

From ear via CN VIII; ventromedial pathway down to ipsilateral proximal limb and axial muscles to keep balance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Reticulospinal path

A

Input from motor cortex; descend ipsilaterally to act on alpha and gamma MNs; probably to do with postural adjustment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Tectospinal path

A

Input from retina to superior colliculus in midbrain; sends input across the midline to muscles that turn head towards stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Decortication

A

Lesion at superior midbrain, projections from midbrain intact; arms are adducted, legs extended and rotated inward

17
Q

Decerebration

A

Lesion at superior pons; arms extended, wrists flexed, legs extended