Introduction to Neuropathology- Myopathology Flashcards
What is an “onion bulb” characteristic of?
segmental demyelination
Lost muscle is replaced with _____.
adipose and collagen
This is a group of 100-200 myofibers all innervated by the same motor neuron.
the motor unit
What is myopathy?
primary disease of muscle characterized by:
- proximal weakness
- elevated CK
- EMG changes
All fibers in a motor unit are of the same ______ type, either _____ or ______.
histochemical; type 1 or type 2
Describe type 1 muscle fibers.
- more oxidative enzymes
- more mitochondria
- more myoglobin
- increased tonic firing
- decreased rate of contraction and relaxation
Which muscle fiber type?
- more glycolytic enzymes
- increased rate of fatigue
type 2 (fast-white)
What comprises the DAC?
- dystroglycans (2)
- sarcoglycans (5)
What are the 3 patterns of peripheral neuropathy?
- Wallerian degeneration
- distal axonopathy
- segmental demyelination
This is an enzyme that moves phosphate from creatine phosphate to ADP.
creatine kinase (CK)
This is distal weakness and atrophy with normal CK and different EMG changes.
denervation
Where do capillaries run in a muscle?
in the endomysium
During contraction, actin and myosin _____ to shorten the sarcomere by 20%.
slide into each other
In muscular dystrophy, _____ increase and replace lost muscle, also causing stiffness.
endomysial fibrous and adipose tissue
This is the distance btw two z-bands.
a sarcomere
What is perineurium?
a sheath of special, fiber-like cells that tie the axons of each fascicle together
When the sarcolemma is damaged, _____ leaks into the serum.
creatine kinase (CK)
_____ filaments are attached to z-bands.
Actin
Myofibers contain 2 kinds of contractile filaments: ____ and _____.
myosin and actin
Describe type 2 muscle fibers.
- more glycolytic enzymes
- increased rate of fatigue
What causes distal axonopathy?
- drugs
- industrial poisons (pesticides, organic phosphates, solvents)
Which muscle fiber type?
- more oxidative enzymes
- more mitochondria
- more myoglobin
- increased tonic firing
- decreased rate of contraction and relaxation
type 1 (slow-red)
What is the motor unit?
group of 100-200 myofibers all innervated by the same motor neuron
Actin filaments are attached to _____.
z-bands
What nerves are most affected by distal axonopathy and why?
large axons bc they have the highest metabolic and nutritional demands
What determines if the fibers in a motor unit are type 1 or type 2?
the nerve supply
What is endoneurium?
the small amount of matrix in between individual axons
What neuropathies can show segmental demyelination?
- inflammatory demyelinative neuropathies
- Charcot-Marie-Tooth disease
What causes Wallerian degeneration?
- trauma
- peripheral nerve infarction
- neoplastic infiltration
What are the 2 fiber types in muscles?
- type 1 (slow-red)
- type 2 (fast-white)
Myofibers are bound to the extracellular matrix by chain of proteins consisting of ____ and ______.
- dystrophin
- the dystrophin-associated complex (DAC)
What does CK do?
it’s an enzyme that moves phosphate from creatine phosphate to ADP
In _____, degeneration of the axon and myelin develops first in the most distal parts of the axon.
distal axonopathy
What is a sarcomere?
the distance btw two Z-bands
Each muscle is wrapped by a fibrocollagenous sheath called the ______.
perimysium
What is the other source of energy that isn’t used for muscle contraction, but to replenish ATP?
phosphocreatine
Muscle disease can be placed into 2 broad categories: _____ and _____.
- myopathy
- denervation atrophy
What is the rate of axonal growth in Wallerian degeneration?
1-2 mm/day (faster if closer to the cell body)
The immediate source of energy for muscle contraction is ______.
hydrolysis of ATP
What is segmental demyelination?
the breakdown and loss of myelin over a few segments, but the axons remain intact and the neuronal body doesn’t change
What is Wallergian degeneration?
an axon is transected and central chromatolysis occurs (smooth cytoplasm, displaced nucleus) to disintegrate and degrade the old axon and grow a new one from the proximal stump
What is an “onion bulb” formation?
concentric layers of Schwann cell processes and collagen around an axon
This is primary disease of muscle characterized by proximal weakness, elevated CK, and EMG changes.
myopathy
