muscle structure and function Flashcards
what do muscles do
Produce movement
* Maintain postures and positions
* Other functions – protection, heat production (themogenesis)
and driving circulatory system (vascular pump)
3 types of muscles
smooth muscle
cardiac muscle
skeletal muscle
what are muscle fibers
Muscle consists of bundles of fibres (fascicles) and each fibre can individually contract
how do muscle fibers contract
Each contractile fibre generates tension, which applies force to both ends
what is a Musculo-tendon contraction
Forces generated by individual fibres are gathered in tendons and the resultant force pulls the bone
parallel vs pennate muscle fibers
Pennate muscles are stronger because more fibres are packed
Pennate muscles have greater PCSA
Physiological Cross-Sectional Area (PCSA)
Area of the cross section of a muscle perpendicular to its fibres
parallels vs pennate speed
Pennate muscles are slower because fibres have to shorten over a
greater distance to shorten the muscle over the same distance
3 types of muscle contraction
When external force = muscle force, muscle length
will stay constant: Isometric contraction
▪ When external force < muscle force, muscle can be
shortened while contracting: Concentric contraction
▪ When external force > muscle force, muscle can be
lengthened while contracting: Eccentric contraction
what are myofibrils made of
sacromere
what are sarcomere made of
A sarcomere consists of two “inter-digitated” myofilaments:
actin (thin) and myosin (thick) filaments
sliding filament theory
Actin and myosin filaments slides towards each other
▪ The main source of the sliding forces comes from interactions between
myosin heads and actin binding sites, called cross-bridges.
terminology
Binding sites: positions on actin filaments where the myosin head can attach
▪ Cross-bridges: temporarily formed mechanical bridges between actin binding
sites and myosin heads
▪ Power stroke: a ‘nod’ of the myosin head that applies force to the actin
filament via the cross-bridge
