Muscle Flashcards
Myalgia means
Muscle pain
Myasthenia means
Weakness of the muscle
Myocardium is
The muscular component of the heart
Myopathy is
Any disease of the muscles
Myoclonus is
A sudden spasm of the muscles
Red skeletal muscle fibres are:
- Smaller
- Richly vascularised
- Contraction is slow, repetitive and weaker
- Fatigue slowly
White skeletal muscle fibres are:
- Larger
- Poorly vascularised
- Low in mitochondria
- Faster and stronger
- Fatigue rapidly
Intermediate muscle fibres:
Are in between on all characteristics
Myoglobin is present in which types of muscle?
Skeletal and cardiac muscle
A muscle fibre is:
A striated muscle cell
When destruction of muscle > replacement this is called:
Atrophy
When replacement < destruction this is called
Hypertrophy
Skeletal muscle is composed of…
Fascicles composed of
Muscle fibres composed of
Myofibrils composed of
Myofilaments (actin and myosin)
What forms the thin filaments of skeletal muscle and cardiac muscle?
Actin, tropomyosin and troponin
Why are troponin assays a useful diagnostic tool?
Troponin used as a marker for cardiac ischaemia
Released from ischaemic cardiac muscle within an hour
Must measure within 20 hours
Used by emergency units as the assay of choice
What is Creatine Kinase?
Is an important enzyme in metabolically active tissues like muscle
Can be used to diagnose heart attacks
Enzyme increase is largely largely proportional to infarct size
Sequence of events in sliding of thin filaments during contraction:
1) Myosin cross bridge attaches to actin myofilament
2) The myosin head pivots and bends and slides the actin filament toward the M line (ADP and P released)
3) New ATP attaches to the myosin head, cross bridge detaches
4) As ATP is split into ADP and P, cocking of the myosin head occurs
What is the neuromuscular junction?
Small terminal swellings of the axon containing acetylcholine
Striated muscle appears as:
A dark A band and a lighter I band.
There is more detail - Z, M, H
Cardiac muscle appears as:
Striated, central nuclei, intercalating discs, branching
What is ANP?
Atrial natriuretic peptide
28 amino acid peptide synthesised, stored and released by atrial monocytes.
Stimulated by hypervolemic states (elevated blood volume)
What is BNP?
Brain-type natriuretic peptide
32 amino acid peptide synthesised largely by the ventricles and the brain.
Pro-BNP (108aa)
N terminal pro BNP (76aa)
BNP and NT-pro-BNP are markers for heart failure
What do natriuretic peptides do?
They serve as a counter-regulatory system for the renin-angiotensin-aldosterone system
Structural characteristics of Purkinje fibres:
Abundant glycogen
Sparse myofilaments
Extensive gap junction sites
Structural characteristics of smooth muscle:
- Cells are spindle shaped
- Central nucleus
- Non striated
Where is smooth muscle typically found?
Walls of passageways or cavities
What are myoepithelial cells?
Stellate cells forming a basketwork around the secretory units of some exocrine glands
What are myofibroblasts?
Produce collagenous matrix but also contract (abundant acts and myosin)
How are the thin and thick filaments arranged within the cell?
Diagonally
Can skeletal muscle cells divide?
No. But they can regenerate by mitotic activity of satellite cells.
Is cardiac muscle capable of regeneration?
No. Following damage, fibroblasts lay down scar tissue.
Can smooth muscle cells divide?
Yes. They retain their mitotic activity and can form new cells.
