Brainscape's Knowledge GenomeTM

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


See full index

Neuroscience > Lecture 4: PNS Injury and Repair > Flashcards

Lecture 4: PNS Injury and Repair Flashcards

1
Q

where are upper motor neurons?

A

originate in the cerebral cortex and brainstem and govern the activity of lower motor neurons in the brainstem and spinal cord

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

where are lower motor neurons

A

once it reaches the anterior horn of the spinal cord

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

what are the 2 types of lower motor neurons

A

alpha motor neurons

gamma motor neurons

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

what are alpha motor neurons

A

LMNs that innervate extrafusal muscle fibres for muscle contraction

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

what are gamma motor neurons

A

LMNs that innervate intrafusal muscle fibres (muscle spindles)

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

what are the two times of alpha motor neurons

A

somatic motor (cell body in the anterior horn)

cranial nerves (originate in the brainstem

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

what is a motor unit

A

The alpha motor neuron and the skeletal muscle fibres it innervates

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

do we have more alpha motor neurons or muscle fibres in the body

A

way more muscle fibres

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

what is the purpose of Cervical and lumbosacral enlargements in the spinal cord

A

to accomodate extra motor units

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

Spinal nerves are made up of which two types of roots

A

posterior (sensory Afferent ) roots

anterior (motor efferent) roots

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

if a spinal nerve is injured, would there be motor or sensory issues

A

both

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

what do Spinal nerves split to become

A

posterior and anterior rami

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

UPDATE ANSWER

what separates to terminal branches / peripheral nerves

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

what is a dermatome

A

an area of skin that is mainly supplied by afferent nerve fibres from
the dorsal root of a spinal nerve

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

what is a peripheral nerve

A

terminal branches of the PNS

Mixed (motor and sensory)

Cranial nerves are also peripheral nerves

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

where is the damage in an Upper Motor Neuron Syndrome

A

Damage to the descending tract before it synapses in the anterior horn of the spinal cord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

where is the damage in a Lower Motor Neuron Syndrome

A

Damage to alpha motor neuron at or distal to the anterior horn

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

what are symptoms of an upper motor neurone lesion

A

(proximal to anterior horn)

hypertonia

hyperreflexia

positive babinski and Hoffman’s test

normal nerve conduction tests and EMG

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are the symptoms of a lower motor neuron lesion

A

(at or distal to the anterior horn)

Weakness/paralysis/paresis

hypotonia

hyporeflexia

negative babinski and Hoffman’s test

a lot of atrophy

abnormal nerve conduction tests and EMG

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

if there was a lesion on the right side of the brain in the cerebral cortex or the brain stem, what would we excect to see

A

spastic paresis (hypertonia) on the opposite side (contralateral) and below lesion

HYPOTONIA AND HYPOREFLEXIA CAN STILL HAPPEN BUT LESS COMMON

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

what would we expect to see if there was a lesion on the spinal cord

A

hypertonia on the same side (ipsilateral) and below lesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what would we see if the incur was at the lower motor neurone or the muscle?

A

flaccid paralysis (hypotonia) ipsilaterally (same side) at the level of injury

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what happens at the many overlaps between UMN and LMN in spinal cord

A

more prone to injury

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what type of neuron is injured during a stroke

A

upper motor lesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what are the symptoms of stroke

A

Usually have some paresis

positive Babinski/Hoffman’s

  • Hyperreflexia
  • Hypertonia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what type of neuron is injured during a spinal cord injury

A

primary upper motor neuron, but can have Lower motor neurons or mixed depending on location of injury

27
Q

why are spinal cord injuries more likely to be upper motor neurons affected of the cervial spine is affected

A

cervical spine has more white matter

28
Q

why are spinal cord injuries more likely to be lower motor neurons affected of the lumbar spine is affected

A

more grey matter in the lumbar spine

29
Q

what are the symptoms of a spinal cord injury

A

Weakness below level of lesion (often bilateral)

Hypertonia and hyperreflexia

Sensory loss below level of lesion

Bladder and bowel involvement

30
Q

what is Amyotrophic Lateral Sclerosis (ALS)

A

Destroys both UMNs and LMNs

dramatic ↓ Number of motor units

fasciculations

Fatigue

31
Q

what is an Alpha Motor Neuron Injury

A

LMN syndrome

Wasting and weaknes

no sensory involvement

32
Q

what is a Spinal Nerve Injury

A

Weakness in distribution of nerve root ( myotomal weakness)

Associated sensory symptoms in same distribution (dermatome)

Pain along sensory distribution

33
Q

what is Peripheral Nerve Injury

A

LMN

Weakness and sensory loss in distribution of affected nerve(s) (ie. radial nerve)

Wasting if severe because muscle isn’t innervated

34
Q

what is Guillain-Barre Syndrome (GBS)

A

peripheral nerve issue, lower motor neurone presentation

Preceded by acute infectious illness

Destruction of myelin sheath with axonal damage

Rapidly progressing motor and sensory impairments

35
Q

what are the 3 classifications of peripheral nerve injuries

A

neuropraxia

axonotmesis

neurotmesis

36
Q

what is neuropraxia

A

Focal myelin injury

axon is intact

most mild

37
Q

what is axonotmesis

A

Injury to axon and myelin but supporting connective tissue intact

crush injury

38
Q

what is neurotmesis

A

Injury to myelin, axon and supporting connective tissue

Complete nerve laceration

39
Q

what is Wallerian degeneration

A

when a nerve fiber is cut or crushed (axonotmesis or neurotmesis) and part of the distal axon degenerates

can happen with axonotmesis or neurotmesis

40
Q

what 3 things are we looking at the results of a muscle being stimulated with nerve conduction studies

A

amplitude

Latency

conduction velocity

41
Q

what is amplitude in Nerve Conduction Studies

A

how many axons are being stimulated

42
Q

what is latency in Nerve Conduction Studies

A

time between stimulation and result

Most affected by demyelination

43
Q

what is conduction velocity in Nerve Conduction Studies

A

Distance/time

Affected by both axonal loss
and demyelination

44
Q

what is axonal loss in Nerve Conduction Studies

A

abnormal motor response

lower amplitude

45
Q

what is demyelination in Nerve Conduction Studies

A

Latency prolonged

Conduction velocity slow

46
Q

what is Motor unit potential

A

Summation of electrical activity of the
muscle fibres of the motor unit

47
Q

what are the 2 types of peripheral nerve recovery

A

Axonal Repair and Regrowth

Collateral Sprouting

48
Q

what does regrowth of the axon result in

A

reinnervation of the target muscle

Regeneration is faster closer to injury site and slower further away

49
Q

what are the 2 key players in axonal regrowthand their function

A

Macrophages clear away degenerating parts

Schwann cells act as a guide and stimulate regrowth

50
Q

How do Schwann cells support axonal regrowth?

A

Growth cone extends to search for target

Provide a framework to help guide growing axons

Secrete neurotrophic signals that promote axon growth

51
Q

do Crush injury (axonotmesis) always result in Wallerian degeneration

A

no but its always in neurotmesis

52
Q

why do crush injuries (axonotmesis) not always result in wallerian degeneration

A

Schwann cell framework less disrupted which help guide the regenerating proximal segment

Recovery is often more rapid (and complete) in a crush vs. cut injury

53
Q

how are severed nerves reconnected

A

if severe, reapportion surgery is needed

54
Q

are Schwann cells unable to regrow with extensive damage

A

no. new Schwann cells can regrew

55
Q

what happens if there is a severe injury and distal end is not available for reapposition

A

outcomes tend to be poor

56
Q

who is Henry Head

A

he Surgically transected his own radial nerve

57
Q

Can We Fast-Track peripheral nerve regeneration?

A

evidence demonstrating a positive effect of exercise on nerve regeneration is at best poor

58
Q

what is collateral sprouting

A

Many diseases, and even healthy aging, can decrease the number of motor units in humans

motor unit sprouts new axons to reinnervate damaged muscle fibres, so motor unit increase in size

59
Q

why do we see a larger amplitude in lower motor neuron conditions

A

more muscle fibres are excited

more muscle fibres are adopted into the motor unit so motor fibres are lost but the size of motor units are larger

60
Q

progressive muscle weakness, hyporeflexia, and paralysis. She suddenly developed weakness and tingling sensations in her legs and arms that gradually progressed over the course of a few days. She eventually found it difficult to walk and perform her ADLs.

Do you think this is an UMN or LMN condition?

A

lower motor neuron

hyperreflexia

weakness

61
Q

progressive muscle weakness, hyporeflexia, and paralysis. She suddenly developed weakness and tingling sensations in her legs and arms that gradually progressed over the course of a few days. She eventually found it difficult to walk and perform her ADLs.

What condition do you think Emily has?

A

Guillain-Barre Syndrome (GBS)

62
Q

where do we see damage with polio

A

anterior horn cells

63
Q

what was recovery with polio due to

A

motor unit collateral sprouting

Neuroscience (10 decks)

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