Skeletal Muscle Flashcards
where is visceral/smooth muscle found?
- arterial wall
- wall of intestine
- airways of lungs
where is voluntary/skeletal muscle found?
- skeletal muscles
- larynx
- diaphragm
where is cardiac muscle found?
- heart
* base of great vessels
name 3 other contractile cells
- pericytes
- myo-fibroblasts
- myo-epithelial cells
what are the layers of connective tissue in skeletal muscle?
- endomycium
- perimycium
- epimycium
what does skeletal muscle start as in embryonic life?
myoblasts
describe the embryonic development of skeletal muscle
- individual precursor myoblasts fuse together to form muscle fibres
- a single muscle fibre will form from the fusion of hundreds of myoblasts
⇒ individual muscle fibres are multinucleated
where are nuclei in skeletal muscles?
pressed towards the cell membrane
- unlike in smooth & cardiac muscle
what are the components of skeletal muscle?
- sarcolemma
- multiple nuclei
- contractile proteins
- mitochondria
- sarcoplasmic reticulum
- glycogen-rich sarcoplasm
- T-tubular system
what is the t-tubular system?
specialised network of tubules that convey calcium into the cytoplasm of the cell
describe the histological appearance of skeletal muscle
- elongated fibres
- striated cytoplasm
- multinucleate
- nuclei at edges
- non-branching
why is skeletal muscle striated?
myofibrils in register
what is a myofibril
arrangement of contractile proteins within a muscle fibre
how many sarcomeres does each myofibril contain?
multiple
what is a sarcomere?
functional units of the myofibril
- material between two Z lines
what does each sarcomere contain?
- actin
- myosin
- accessory proteins
what is the appearance of actin?
- thin
- light
what is the appearance of myosin?
- thick
- dark
what does actin give rise to?
isotropic (I) bands
what does myosin give rise to?
anisotropic (A) bands
what are the types of skeletal muscle fibre?
- type 1
- type 2
what are the similarities between type 1 and type 2 skeletal muscle fibres?
rich in fibrillar ATPase
how do type 1 skeletal muscle fibres obtain energy?
oxidative phosphorylation
where are type 1 skeletal muscle fibres found?
muscles that maintain posture
what are slow twitch muscle fibres?
type 1
- fatigue resistant
what are fast twitch muscle fibres?
type 2
how do type 2a muscle fibres obtain energy?
oxidative & glycolytic metabolism
- some fatigue resistance
how do type 2b muscle fibres obtain energy?
glycolysis
- fatigue sensitive
how would you distinguish the types of skeletal muscle fibre histologically?
histochemical stain looking for ATPase
what is the function of muscle spindles?
Detect stretch and tension
describe the structure of muscle spindles
- fibrocollagenous capsule
- intrafusal muscle fibres wrapped around gamma efferent nerve fibres
where is the endomysium?
between individual muscle fibres
what is the function of the perimysium?
binds groups of muscles together to form fascicles
what is the function of the epimysium?
binds fascicles together
what is the function fo sharpey’s fibres?
connect muscle to bone (and penetrate bone)
describe the structure of sharpey’s fibres
bundles of collagen linking epimysium to periosteum
what is the function of tendons?
connect muscle to bone
describe the structure of tendons
- parallel bundles of collagen
- intervening fibroblasts
