Muscle in health and disease Flashcards
-review basic structure and function of skeletal muscle -functions of skeletal muscle -C.T. sheaths -fibre types -DD for muscle disorders -infantile hypotonia --polymyositis/dermatomyositis -
main component in muscle
water -80%
what is muscle a store for
water + glycogen + intracellular ions (ex: K+)
4 functions of skeletal muscle
- movement
- maintain posture
- joint stability
- generate heat (S.E heat production)
Can skeletal muscle repair itself?
YES - has stem cells -able to regenerate muscle fibres- last lifetime - get less efficient with age
What are the 2 different types of muscle fibres?
type 1 - slow twitch - RED
type 2- fast twitch - pale pink/WHITE
identify different muscle fibres in a muscle biopsy by ATPase staining
What are the different types of type 2 muscle fibres?
type 2a = fastest rate of contraction - AEROBIC - WHITE type 2b(x)= fast rate of contraction - ANAEROBIC - PINK
Name an example of a muscle high in type 1 fibres?
soleus - calf muscle- maintains posture
Name a muscle high in type 2a fibres
extraocular eye muscles
Name a muscle high in type 2b(x) fibres
GASTROCNEMIUS- calf muscle - knee flexion + plantarflexion = walking/running/posture
Review histology of skeletal muscle
- nuclei
- size of fibres
- sarcomere arrangement
- cell type
- peripheral nuclei
- muscle fibre size are all equal
- sarcomere aligned (striations match up from sacromere-to-sacromere)
- multinucleate cell- several muscle cells-fuse to 1 - 1 muscle cell runs length of muscle fibre - synchronorous + powerful contraction
what is a sarcomere
contractile unit of muscle fibre - made up from contractile filamnetous proteins - ACTIN + MYOISN
what is the relation of connective tissue to muscle
C.T is closely related to muscle - forms sheaths around muscle
3 places disease can affect in muscle
- muscle
- associated C.T sheath
- NMJ
what is epimysium
C.T sheath surrounding muscle (organ)
what is perimysium
C.T sheath surrounding FASICLE (group of muscle fibres)
what is endomysium
C.T sheath surrounding individual muscle fibre
what is a motor unit (MU)
MN + all the muscle fibres it innervates
what is the result of loss innervation of a single MN
- loss of innervation to all muscle fibres supplied by the MN
- muscle fibres ATRPOHY + SMALLER + ANGULATED
How can muscle fibres be re-innervation following loss of its MN innervation
Remaining, healthy MN sprout to innervate DE-INNERVATED fibres
- MU enlarges
- fibre type grouping
- group atrophy
Infantile hypertonia
- define
- another name
- cause - 2 types
- histological changes
- prognois
- decreased muscle tone
- floppy baby syndrome (test-baby on back- cannot lift head)
- type 1 fibres larger +small type 2 fibres or vice versa - muscle unable to function properly
- abnormally small +round muscle fibres & groups of hypertrophic muscle fibres
- normal LE + QOL + only issue is inability to EXERCISE