1. Chapter 36 Disorders of Neuromuscular Function
Essentials of Pathophysiology
Chapter 36 Disorders of Neuromuscular Function

2. Pre lecture quiz (True / false)
Paralysis refers to weakness or incomplete loss of muscle function.  
Carpal tunnel syndrome is an example of a polyneuropathy.
All levels of spinal cord injury will require assistance to maintain breathing.
Autonomic dysreflexia represents an acute episode of exaggerated sympathetic reflex responses that occur in persons with some types of spinal cord injuries.
The pathophysiology of multiple sclerosis involves the demyelination and subsequent degeneration of nerve fibers in the central nervous system. F T

3. Pre lecture quiz Acetylcholine Fibers Ganglia Tic Weakness
Myasthenia gravis, an autoimmune disorder, is caused by an antibody-mediated destruction of ______________________ receptors in the neuromuscular junction.
Guillain-Barré syndrome is characterized by progressive ascending muscle _____________________ of the limbs, producing a symmetric flaccid paralysis.
Parkinson disease is a degenerative disorder of the basal ___________________ that results in variable combinations of tremor, rigidity, and bradykinesia.
A __________________ is a an irregularly occurring, brief, repetitive movement such as winking, grimacing, or shoulder shrugging.
Muscular dystrophy is a term applied to a number of genetic disorders that produce progressive degeneration and necrosis of skeletal muscle __________________, which are eventually replaced with fat and connective tissue.
Acetylcholine
Fibers
Ganglia
Tic
Weakness

4. Upper Motor Neurons Are in the Brain and Spinal Cord
Upper motor neuron cell bodies are in the motor cortex
They send their axons down through the internal capsule
The axons then run down the white matter of the spinal cord

5. Two Motor Systems Extrapyramidal Pyramidal
Most go to same side of body
Pyramidal
Most cross to other side of body
Motor cortex neurons
Internal capsule
Pons
Extrapyramidal
Pyramidal system
system

6. Lower motor neuron’s axon running through peripheral nerves
Motor Unit
Lower motor neuron
Lower motor neuron’s axon running through peripheral nerves
The muscles it innervates
Upper motor neurons
Send axons down
spinal cord tracts
Lower motor
neurons in spinal
cord
Peripheral nerves
Muscles

7. Question
Which motor neurons are damaged in patients who have neuromuscular disorders that directly affect skeletal muscle?
Upper
Lower
Both upper and lower
Neither upper nor lower

8. Answer
Lower
Rationale: The axons of lower motor neurons pass through peripheral nerves to effector tissue in skeletal muscle. Upper motor neurons’ axons travel down the spinal cord.

9. Muscle Tone Muscle stretches
Afferent neuron carries impulse to spinal cord
Motoneurons cause muscle to contract

10. Alterations in Muscle Tone
Hypotonia
Hypertonia
Rigidity
Clonus

11. Terms to Describe Motor Dysfunction
-plegia = stroke or paralysis
Paralysis = loss of movement
-paresis = weakness
Mono- = one limb
Hemi- = both limbs on one side
Di- or para- = both upper limbs or both lower limbs
Quadri- or tetra- = all four limbs

12. Discussion What would be the terms for the following?
A defect causing weakness in both arms
A weakness in the right arm and leg
Inability to move one leg

13. Upper vs. Lower Motor Neurons
Upper motor neurons
In the brain and spinal cord
Lower motor neurons
Send axons out of the spinal cord
Upper motor neurons
Send axons down
spinal cord tracts
Lower motor
neurons in spinal
cord
Peripheral nerves
Muscles

14. Upper Motor Neuron Damage
Weakness and loss of voluntary motion
Spinal reflexes remain intact but cannot be modulated by the brain
Increased muscle tone
Hyperreflexia
Spasticity

15. Lower Motor Neuron Damage
Neurons directly innervating muscles are affected
Irritated neurons
Spontaneous muscle contractions: fasciculations
Death of neurons
Spinal reflexes are lost
Flaccid paralysis
Denervation atrophy of muscles

16. The Motor Unit One lower motor neuron (motoneuron)
The neuromuscular junction
The muscle fibers it innervates

17. Question
Tell whether the following statement is true or false. To increase the strength of a contraction, more motor neurons must be recruited.

18. Answer
True Rationale: A motor unit consists of branches of a neuron and the skeletal muscle fibers that they innervate. For stronger contractions, more motor units are required.

19. Possible Problems With the Motor Unit
Lower motor neuron lesions or infections; peripheral nerve injury
Neuromuscular junction disorders
Muscle atrophy or dystrophy

20. Skeletal Muscle Problems
Disuse atrophy
Denervation atrophy
Muscular dystrophy
Contractile proteins not properly attached to cytoskeleton of muscle cell
Protein movement does not effectively contract muscle cell

21. Neuromuscular Junction Problems
Decreased acetylcholine release
Botulism
Decreased acetylcholine effects on muscle cell
Curare
Myasthenia gravis
Decreased acetylcholinesterase activity; acetylcholine has a stronger effect on the muscle cell
Organophosphates

22. Question
Tell whether the following statement is true or false. Acetylcholinesterase stimulates the release of acetylcholine (ACh).

23. Answer
False Rationale: Acetylcholinesterase breaks down ACh, resulting in relaxation of the skeletal muscle.

24. Myasthenia Gravis Autoimmune disease Gradual development of weakness
Gradual destruction of acetylcholine receptors
Associated with thymus tumor or hyperplasia
Gradual development of weakness
From proximal to distal portions of body
Myasthenia crisis: respiration compromised

25. Peripheral Nerve Injuries
Damage to LMN cell bodies in the spinal cord
Damage to axons in the spinal or peripheral nerves
Damage to myelin sheath (demyelination)

26. Peripheral Nerve Injuries (cont.)
Mononeuropathies
Damage to one peripheral nerve
E.g., carpal tunnel syndrome
Polyneuropathies
Damage to many peripheral nerves
E.g., Guillain-Barré syndrome

27. Back Pain Peripheral nerve injury at the spinal nerve roots
Often due to compression of nerve root by vertebrae or vertebral disk

28. Motor Impulses Are Modulated by the Basal Ganglia
Upper motor neuron cell bodies are in the motor cortex
They send their axons down through the internal capsule
The basal ganglia inhibit and modulate movement patterns

29. Basal Ganglia Dysfunction Can Increase Patterned Movement
Tremors
Tics
Hyperkinesia
Choreiform: jerky movements
Athetoid: continuous twisting movements
Ballismus: violent flinging movements
Dystonia: rigidity

30. Question
Which disease is a result of basal ganglia dysfunction?
Myasthenia gravis
Multiple sclerosis
Polio
Tourette syndrome

31. Answer
Tourette syndrome
Rationale: The tics and hyperkinesia that often accompany Tourette syndrome are typical of basal ganglia dysfunction (the function of the basal ganglia is movement control).

32. Parkinsonism Tremor Rigidity Bradykinesia (slow movement)
Loss of postural reflexes
Autonomic system dysfunction
Dementia

33. Cerebellum Damage Vestibulocerebellar disorders
Difficulty maintaining posture
Cerebellar ataxia
Movements divided into separate components
Cerebellar tremor

34. Amyotrophic Lateral Sclerosis
Damages both upper and lower motor neurons
UMN damage  weakness, lack of motor control
Loss of control over spinal reflexes  stiffness, spasticity
LMN damage
Irritation  fasciculations
Decreased neuron firing  weakness, denervation atrophy, hyporeflexia

35. Multiple Sclerosis
Destruction of myelin coating on axons
Demyelinated or sclerotic patches develop through white matter of CNS
Decreased conduction velocity

36. Question
Which disorder causes damage to both upper and lower motor neurons?
ALS MS
Myasthenia gravis
Parkinson disease

37. Answer
ALS
Rationale: Also known as Lou Gehrig disease, ALS destroys both upper and lower motor neurons. Typical S/S include weakness, lack of motor control, denervation atrophy, and hyporeflexia.

38. Spinal Cord Injury Immediate damage causes: Spinal cord shock
Temporary complete loss of function below injury
Primary neurologic injury
Irreversible damage to neurons

39. Secondary Injury to the Spinal Cord
Neurons and white matter in area of initial damage are affected
Possible causes include:
Damage to blood vessels supplying the area
Decreased vasomotor tone decreasing blood supply
Local release of substances that cause vasospasm
Release of digestive enzymes from damaged cells

40. Partial Spinal Cord Injury
Central cord syndrome: damage to axons near the gray matter
Arms more affected than legs
Anterior cord syndrome: damage to anterior section of cord
Motor functions affected; touch sensation not affected
Brown-Séquard syndrome: damage to one side of cord
Motor function lost on that side; pain/temperature sensation lost from other side

41. Complete Spinal Cord Injury
To upper motor neurons (T12 and above)
Spinal reflexes still work
No longer modulated by brain
Hypertonia, spastic paralysis
To lower motor neurons (T12 and below)
Cells in spinal reflex arcs damaged
Flaccid paralysis