4. Spinal Cord: Motor Unit And Reflexes 3

Front 1

4 Levels of the motor unit at which damage can occur:

Back 1

1. Muscle
2. NMJ
3. Nerve axon
4. Motor neuron

Front 2

Where are LMNs?

Back 2

Spinal cord

Front 3

Where are UMNs?

Back 3

Brainstem/cortex

Front 4

Where can damage affect the sensory component of a spinal reflex?

Back 4

-Afferent nerve
-DRG

Front 5

What is a myopathic disease?

Back 5

One that is caused by an intrinsic abnormality in the muscle.

Front 6

What is a neuropathic disease?

Back 6

A disease that causes abnormalities in peripheral nerves

Front 7

Where will neuropathic diseases be more pronounced? Why?

Back 7

More distally than proximally, bc the magnitude of disease is proportional to axon length.

Front 8

What is a neurogenic disease?

Back 8

One that interrupts normal innervation of a muscle - denervation or renervation.

Front 9

What is Muscular Dystrophy?

Back 9

A general category for a group of inherited chronic disorders that are myopathic.

Front 10

What causes symptoms in MD?

Back 10

Muscle degeneration that causes progressively worse weakness.

Front 11

4 major types of MD:

Back 11

1. Duchenne's MD
2. Facioscapulohumeral
3. Myotonic dystrophy
4. Limb-girdle MD

Front 12

In whom is Duchenne's MD most common?

Back 12

Children

Front 13

What is the characteristic feature of Duchenne's MD?

Back 13

Wasting and weakness in the pelvic muscles.

Front 14

What does Facioscapulohumeral MD affect?

Back 14

The face and shoulder girdle

Front 15

What form of MD is most common in adults?

Back 15

Myotonic MD

Front 16

Characteristic feature of Myotonic MD:

Back 16

Inability to relax muscles after strong contraction - especially hands.

Front 17

What is affected in Limb-Girdle MD?

Back 17

Proximal muscles in the pelvic and shoulder girdle.

Front 18

What type of inheritance is Duchenne's MD?

Back 18

X-linked recessive

Front 19

Does Duchenne's MD only affect males?

Back 19

No; females can be carriers

Front 20

What is the incidence of Duchenne's MD?

Back 20

1/3500 males born

Front 21

When is the onset of Duchenne's MD seen?

Back 21

When boys begin to walk

Front 22

What is the usual outcome of Duchenne's MD?

Back 22

Death by age 20-30 due to respiratory complications.

Front 23

Primary symptoms of Duchenne's MD:

Back 23

Waddling, lurching gate; skeletal deformities.

Front 24

2 tests for Duchenne's MD:

Back 24

-Gower's maneuver
-CK serum levels high

Front 25

What does Gower's maneuver test show?

Back 25

Patients push up from the ground very slowly.

Front 26

Why are serum CK levels high in duchenne's MD?

Back 26

B/c damaged muscles leak CK into the bloodstream.

Front 27

What is the Cause of Duchenne MD?

Back 27

Lack of the gene for Dystrophin

Front 28

What is Dystrophin?

Back 28

A protein that anchors actin in the cytoskeleton to the muscle membrane.

Front 29

What happens when Dystrophin is lacking?

Back 29

The sarcolemma is weak and subject to shearing and tearing.

Front 30

What results from shearing and tearing of the sarcolemma?

Back 30

Calcium influx and muscle necrosis.

Front 31

What is Becker MD and what causes it?

Back 31

Very similar to Duchenne's but less severe; caused by lack of dystrophin.

Front 32

How does a child with Duchenne's MD stand?

Back 32

In a lordotic posture - like brenty

Front 33

What is the major disease of the Neuromuscular junction?

Back 33

Myasthenia gravis

Front 34

2 forms of myasthenia gravis:
which is more rare?

Back 34

-Autoimmune (more common)
-Congenital (more rare)

Front 35

What is the problem in the autoimmune form of Myasthenia gravis?

Back 35

An autoantibody to the acetylcholine receptor impairs transmission at the NMJ synapse.

Front 36

What type of cholinergic receptor is on muscles?

Back 36

Nicotinic

Front 37

What happens when autoantibodies bind nicotinic ACh receptors?

Back 37

The Ab crosslinks receptors, and triggers internalization and degradation of the receptor.

Front 38

So what 2 main things happen in myasthenia gravis?

Back 38

1. Auto-Ab impairs transmission
2. Degradation reduces number of receptors

Front 39

Net effect of Auto-Ab binding:

Back 39

Reduced number of functional ACh receptors.

Front 40

3 changes that occur when ACh receptors are decreased:

Back 40

1. Decreased amplitude of EPPs
2. APs fail to fire in some muscles
3. ACh depletes w/ repeated firings

Front 41

What is the net effect of reduced numbers of ACh receptors?

Back 41

Skeletal muscle becomes weak and fatigued.

Front 42

What is the normal turnover rate of ACh receptor degradation?

Back 42

5-7 days

Front 43

What is the turnover rate of ACh receptor degradation in myasthenia gravis?

Back 43

2.5 days

Front 44

Clinical symptoms of Myasthenia gravis:

Back 44

-Drooping eyelids, slurring, difficulty breathing.

Front 45

Peak age of myasthenia gravis pt
-Women
-Men

Back 45

Women peak at 20-30 yrs old
Men peak at 50-70 yrs old

Front 46

What gland is implicated in Myasthenia gravis?

Back 46

Thymus

Front 47

Why the thymus?

Back 47

Bc it gets a tumor and that's where the autoantibodies are made.

Front 48

How does the thymus know to make an antibody to the ACh receptor?

Back 48

Myoid cells in the gland have the receptor, which is antigenic.

Front 49

Surgical Treatment for myasthenia gravis:

Back 49

Removal of thymus - 50% of patients go into remission.

Front 50

Nonsurgical treatments of myasthenia gravis:

Back 50

-ACHesterase inhibitors
-Immunosuppressants
-Plasmapheresis

Front 51

What is one ACHesterase inhibitor? What does it do?

Back 51

Pyridostigmine - prolongs the halflife of ACh in the synaptic cleft.

Front 52

Where are LMNs? (2 places)

Back 52

-Spinal cord
-Brainstem

Front 53

What do LMNs do?

Back 53

Directly innervate skeletal muscles

Front 54

Where are UMNs?

Back 54

-Higher brain regions (cortex)
-Brainstem

Front 55

What do UMNs do?

Back 55

Descend and synapse on LMNs to control movement

Front 56

What type of motor neurons are damaged if the symptom is Weak, Wasted, and Twitching muscles?

Back 56

LMNs

Front 57

What type of motor neurons are damaged if the symptom is Overactive Tendon Reflexes?

Back 57

UMNs

Front 58

Spasticity

Back 58

UMN

Front 59

Decreased muscle tone

Back 59

LMN

Front 60

Babinski sign

Back 60

UMN

Front 61

What is the Babinski sign?

Back 61

Abnormal dorsiflexion in response to tickling the toes, instead of normal plantaflexion.

Front 62

Hyperreflexia

Back 62

UMN

Front 63

What disease affects both upper and lower motor neurons?

Back 63

Lou Gherigs

Front 64

Proper name for Lou Gehrig's:

Back 64

ALS - Amyotrophic Lateral Sclerosis

Front 65

What does Amyotrophic mean?

Back 65

Muscle atrophy

Front 66

What does lateral sclerosis mean?

Back 66

Hardness of the spinal cord when the pathologist does the autopsy

Front 67

Why does the spinal cord become hard in ALS?

Back 67

Because of astrocyte proliferation and scarring of the spinal cord lateral columns.

Front 68

What tracts are diseased in ALS?

Back 68

Corticospinal

Front 69

What do the corticospinal tracts normally convey?

Back 69

Info from the premotor cells of the cortex and brainstem to the spinal cord

Front 70

What specific cortical cells are affected in ALS?

Back 70

-Betz cells
-Pyramidal cells in layer V of motor cortex

Front 71

What is usually spared in ALS?

Back 71

-Ocular muscles
-Voluntary bladder sphincter muscles
-Bowel control

Front 72

So what are the symptoms of ALS?

Back 72

Both UMN and LMN symptoms - hyperreflexia, babinski's sign, weakness, twitching, atrophy, cramps.

Front 73

What is the Pseudobulbar effect that is seen in some ALS patients?

Back 73

Uncontrollable bouts of laughter, crying, or explosive speech w/out accompanying emotions.

Front 74

What causes ALS?

Back 74

Don't know

Front 75

Where is the site of peripheral nerve disease?

Back 75

-Axons
-Myelin
-or both

Front 76

Does neuropathy affect only one type of nerve fiber?

Back 76

no; can affect large or small diameter fibers (Abeta or C)

Front 77

Are neuropathies picky about the type of fiber they affect within a given nerve?

Back 77

Yes; while they affect both motor and sensory, they'll pick one to preferentially affect.

Front 78

What is a mononeuropathy?

Back 78

Disease of peripheral nerve that is localized to a focal point.

Front 79

What is a polyneuropathy?

Back 79

Disease of peripheral nerve that is localized globally - generalized.

Front 80

Important causes of peripheral neuropathy:

Back 80

-Diabetes
-Mechanical trauma
-Infections
-Toxins
-Malnutrition
-Immune disorders

Front 81

Is a peripheral neuropathy permanent or reversible?

Back 81

It can be either

Front 82

What is a specific immune neuropathy?

Back 82

Guillian Barre syndrome

Front 83

4 words to describe Guillian Barre:

Back 83

PAID andy griffith and teddy r
Polyneuropathy
Acute
Inflammatory
Demyelinating

Front 84

What makes Guillain barre acute?

Back 84

It has rapid onset and patients often fully recover.

Front 85

What causes Guillain Barre onset?

Back 85

Viral infections

Front 86

What is the pathophysiology of Guillain Barre syndrome?

Back 86

Inflammatory cells and antibodies attack the myelin sheath around peripheral nerves

Front 87

What happens when myelin breaks down?

Back 87

Axons are damaged

Front 88

How are motor nerves affected when their axons are damaged?

Back 88

Conduction slows or is blocked.

Front 89

Symptoms of Guillain Barre:

Back 89

-Crawling skin, tingling
-Hot/cold insensitivity
-Difficulty getting up
-Rapid onset of weakness and paralysis in extremities, breathing muscles, and face

Front 90

What do patients with Guillain Barre LOSE?

Back 90

Reflex to stretch - Areflexia

Front 91

What is the cause of Guillain Barre?

Back 91

Unknown

Front 92

Treatment for Guillain Barre:

Back 92

Plasmapheresis