Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

NOSS > Lower motor neurones > Flashcards

Lower motor neurones Flashcards

1
Q

The lower (or efferent) system can be divided into 2 components - what are these?

A
  • Upper Motor Neurones (UMN)
  • Lower Motor Neurones (LMN)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where are UMN found?

A
  • completely within the CNS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How do the UMN connect to the LMN?

A
  • Connects to LMN directly or via an interneuron
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where are LMN found?

A
  • Cell body in the CNS - within grey matter
  • Axons in the PNS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do LMN connect to muscles?

A
  • via a neuromuscular junction –e.g. all types of muscle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do UMN descend?

A
  • down the CNS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where do LMN start?

A
  • in the spinal cord
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the definition of lower motor neurons? (there are 2 definitions)

A
  • Neurons whose cell bodies located in the spinal cord (for spinal nerves, ventral horn)
  • or in the motor nuclei within the brain (for cranial nerves), whose axons project into the peripheral nervous system to innervate skeletal (voluntary) or smooth (involuntary) muscles.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The LMN include what types of neurons?

A
  • both somatic (voluntary) and autonomic (involuntary) neurones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the LMN sometimes referred to as?

A
  • the common final pathway
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When LMN are stimulated what do they induce?

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

What do LMN function in?

A
  • Maintaining posture, voluntary movement and locomotion – somatic
  • Visceral motor function (glandular secretions, smooth muscle contractions in organs, etc)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Even without AP’s what gets continually released?

A
  • ACh continually released at the neuromuscular junction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Due to acetylcholine leakeage what happens?

A
  • Miniature depolarisations of muscle end plate
  • ‘end-plate noise’ seen on EMG even in inactive muscle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does continual leakage of ACh support?

A
  • supports normal muscle fibre = tone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can you get if there is damaged to the LMN?

A
  • rapid atrophy as no leakage of ACh = no normal tone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is atrophy?

A

= muscle fibres getting smaller – degeneration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

UMN’s are the managers - what does this mean for their function?

A
  • Receive input from motor planning areas of forebrain, cerebellum (coordination) etc
  • When activated, can stimulate or inhibit LMN
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

LMN’s are the workers what does this mean for their function?

A
  • Receive input from UMN
  • Also receive sensory input from muscles as part of reflexes – via little interneuron
  • When activated, cause muscle contraction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Sensory nerves that connect directly to LMN are what?

A
  • reflexes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are muscle spindles?

A
  • sensory organs in muscles
22
Q

What do muscle spindles contain?

A
  • Contain specialised muscle fibre cells (group together in intrafusal fibres)
23
Q

What do muscle spindles detect?

A
  • muscle stretch
24
Q

Sensory neurone from muscle spindle synapses on what?

A
  • LMN’s
25
Q

LMN’s stimulate what and come back out from where?

A
  • LMN stimulates muscle to contract
  • LMN comes back out of ventral horn
26
Q

What does the myostatic (stretch) reflex allow animas to maintain?

A
  • posture
27
Q

During the myostatic reflex what do spindles do?

A
  • send monitoring info to CNS
28
Q

What is the myostatic reflex?

A
  • only monosynaptic reflex as there are no interneurons
29
Q

What does muscle contraction do to muscle spindles?

A
  • Muscle contraction means spindle goes slack… no longer sensitive to stretch
30
Q

But muscles need to be able to detect stretch when they are at different lengths…
Need a mechanism to adjust muscle spindle length and sensitivity - how is this achieved?

A
  • This is achieved with different type of LMN = gamma motor neurons
31
Q

What do gamma motor neurons do?

A
  • Innervate intrafusal muscle fibres in the spindle- they detect stretch
32
Q

How do gamma motor neurons help detect stretch?

A
  • When muscles contract, γ-LMNs stimulate intrafusal fibres to shorten too at the same rate as normal muscle fibres
  • Central sensory part of spindle stays taut
  • muscle can still sense stretching
33
Q

What are ordinary (extrafusal) muscle fibres are innervated by?

A
  • alpha motor neurons
34
Q

What happens when there’s co-activation of alpha and gamma LMN’s?

A
  • make spindle fibres contract at the same time
35
Q

What is a Golgi tendon organ?

A
  • sensory organ within the tendon
36
Q

What does the Golgi tendon organ contain?

A
  • Sensory nerve endings between collagen fibres bundles
37
Q

what does the Golgi tendon organ detect?

A
  • Detects tendon tension within the tendon
38
Q

Where do Golgi tendon organ neurons synapse?

A
  • in the spinal cord
39
Q

How does a muscle automatically relax?

A
  • Sensory neurone from golgi tendon organ on inhibitory interneurone to LMN
  • LMN inhibits, muscle automatically relaxes
40
Q

Why do tendons have reverse myostatic reflexes?

A
  • prevent excessive force through tissues
  • provide monitoring info to CNS
  • Relax tendon and prevents injury
41
Q

What is a good what to test reflexes and localise a problem?

A
  • testing patella reflex
42
Q

How do you test the patella reflex?

A
  1. Hit patellar ligament which…
  2. Stretches the quadriceps (knee extensor muscle)
43
Q

What happens during the patella reflex?

A
  1. Muscle spindle in extensor (quadriceps) detects stretch
  2. Sensory neurone synapses directly with α LMN of extensor – the same muscle
  3. Reflex contraction of extensor to restore muscle length

at the same time …

  • Sensory neurone synapses with inhibitory interneurone (ipsilaterally) – the same side of the body within the spinal cord
  • LMN of flexor muscles inhibited
44
Q

Describe the withdrawal reflex using the example “when you step on fire, you want to withdraw limb quickly”:

A
  • Sensory neurones from skin detect pain
  • Synapse with LMN (via interneurone) in the spinal cord via interneuron
  • Reflex contraction of flexor muscles
  • at the same time there is Ipsilateral relaxation of extensor muscles
  • (Maybe some ascending neurones – tell your brain “ow”)
45
Q

During the withdrawal reflex how do you stop yourself from falling over?

A
  • Synapses with an interneuron which crosses over with other side of body – get contraction which = maintained posture
    – extensors contraction and at the same time there is relaxation of flexors = prevents falling over
46
Q

In the crossed extensor reflex interneurons use both what fibres?

A
  • uses both ipsilateral and contralateral (commissural) fibres
47
Q

In the crossed extensor reflex what happens on the ipsilateral side?

A
  • extensor muscles relax and flexor contract
48
Q

In the crossed extensor reflex what happens on the contralateral side?

A
  • extensor muscles contract and flexors relax
49
Q

If there is a UMN lesion - what happens to:
- reflexes
- atrophy
- tone

A

R - normal/ increase = not directly involved
A- mild, generalised from disuse
T - normal/ increased

50
Q

If there is a LMN lesion - what happens to:
- reflexes
- atrophy
- tone

A

R - decreased/absent
A - severe, rapid, specific muscles
T- decreased/absent

51
Q

What disease can happen in relation to LMN’s?
and describe this:

A
  • Polyradiculoneuritis
    = Idiopathic (or associated with racoon saliva)
    = Inflammatory disorder affecting ventral spinal nerve roots
    = Usually resolves with time, nursing, physical therapy
52
Q

What is myasthenia gravis?

A
  • Auto-immune disease, where antibodies are made against the ACh receptors at the NMJ
  • The antibodies result in decreased numbers of ACh receptors
  • It can be treated with AChE (acetylcholinesterase) inhibitors

NOSS (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions