Muscle pathology Flashcards
What percentage of body mass can skeletal muscle make up, depending on the species?
More than 40%
This varies between different species.
What are the primary functions of skeletal muscle?
- Voluntary and reflective shortening for locomotion and posture
- Respiration
- Food intake
- Eye movements
- Gestures/mimic
- Skilled muscle actions
- Thermogenesis
- Energy homeostasis
- Metabolic adaptation to exercise
What is a motor unit?
The pathway from the lower motor neuron synapse to the muscle fibre that induces contraction.
What neurotransmitter is released at the neuromuscular junction to induce muscle contraction?
Acetylcholine (ACh)
What is the role of calcium ions at the neuromuscular junction?
Induces exocytosis of acetylcholine from the presynaptic membrane.
True or False: Surplus acetylcholine in the synaptic cleft is rapidly deactivated by acetylcholine esterase.
True
What causes the release of calcium ions from the sarcoplasmic reticulum?
The postsynaptic potential via the transverse tubular system.
Fill in the blank: The interaction between thick and thin filaments that causes muscle contraction is dependent on _______ and ATP.
Calcium
What is the consequence of NMJ dysfunction?
Silencing of the NMJ can lead to disuse atrophy.
What is the primary structural component that stabilizes muscle fibers?
Dystrophin glycoprotein complex (DGC)
What are the steps of muscle regeneration following necrosis?
- Necrosis and resorption
- Activation of muscle stem cells
- Proliferation of muscle stem cells
- Differentiation of muscle stem cells
- Maturation of newly formed muscle fibers
- Remodelling of muscle fiber
What histological change indicates maturation of sarcoplasmic elements?
Color shift from basophilic to eosinophilic and restoration of striated pattern.
What are the four main types of muscle disorders based on their primary affection site?
- Interstitial
- Vascular
- Neurogenic
- Myocytic
What is the typical feature of muscle atrophy due to denervation?
Angular atrophy of clustered fibres of both type I and II.
What is the result of metabolic atrophy?
Predominantly affects anaerobic glycolytic type II fibres.
What is the significance of fibre grouping in muscle biopsies?
Typical finding in reinnervation of muscles.
What is myofibrillar myopathy characterized by?
Loss of typical distribution of mitochondria and presence of abnormal protein inclusions.
What is the primary cause of necrotizing myopathy?
Various factors including intoxication, ischaemia, electrolyte shifts, and metabolic impairments.
What type of muscle fibres are primarily involved in postural functions?
Fatigue resistant slow twitch fibres.
What type of muscle fibres are primarily involved in quick phasic movements?
Fatigable fast twitch fibres.
What does a muscle biopsy help to identify in cases of muscle disorders?
Changes in muscle integrity/texture, volume, contraction, relaxation, and muscle pain.
What is a common gross feature of muscle disorders?
Reduction of muscle mass.
What are the histological parameters essential for classifying muscle atrophy?
- Shape
- Distribution
- Type (I vs II) of atrophic fibres
What is the term for when muscle fibres show spontaneous activity due to denervation?
Positive sharp waves and fibrillation potentials.
