Muscle structure and function Flashcards
what are the functions of muscles
- produce movement
- maintain postures and positions
- protection
- heat production (thermogenesis)
- driving circulatory system (vascular pump)
what are the three types of muscle
- smooth (visceral) muscle (involuntary)
- e.g. blood vessels and hollow organs
- cardiac muscle (involuntary)
- e.g. heart
- skeletal muscle (voluntary)
- e.g. connected to bones
what is the balloonist theory
- muscles inflate by stuff in order to get bigger
- ‘animal spirit’ flows from the head to the muscles
- critical prediction: volume of the muscle increases when contracting
what is a bundle of fibers called
fascicle
what is a teno-osseous junction
attaches tendon to bone
what is a musculotendinous junction
attaches tendon to muscle
what is aponeurosis
where the two fiber directions meet
what are the different fiber architectures
- parallel
- all facing same way as muscle
- penniform
- slight angle between fibre direction and muscle direction
- unipennate (1 angle)
- bipennate (2 angles)
- multipennate (3+ angles)
- circular
- flat
- covergent
are pennate or parallel muscles better
- pennate muscles are stronger because fibers are more tightly packed
- pennate muscles have greater PCSA
- pennate muscles are slower because they have to shorten over a greater distance to shorten the muscle over the same distance
what is PCSA
Physiological Cross - Sectional Area
- area of the cross section of a muscle perpendicular to its fibers
why are muscle fibers organised in specific ways
in order to optimise the trade off between strength and speed based on their functional needs
what is an isometric contraction
- when external force = muscle force
- muscle length will stay constant
what is an concentric contraction
- when external force < muscle force
- muscle can be shortened while contracting
what is an eccentric contraction
- when external force > muscle force
- muscle can be lengthened while contracting
what is an agonist muscle
prime mover
what is an antagonist muscle
muscle that has to relax and assists agonist muscle
what are muscle fibers
bundles of myofibrils
what is the meaning of striated
repeating lighter and darker regions of a muscle
what is a sarcomere
- the most basic functional unit of muscle contraction
- consists of actin (thin) and myosin (thick) filaments
what is the A band
the darker region of the sarcomere where the two myosin filaments overlap
what is the I band
the lighter region of the sarcomere where the actin filaments are
what is the m line
the centre of myosin/ centre of A band
what is the z line
the centre of actin/centre of I band
what is sliding filament therory
when the actin and myosin move towards each other to cause muscle contraction
what is a binding site
the positions on actin filaments where the myosin heads can attach
what is a cross bridge
temporarily formed mechanical bridges between actin binding sites and myosin heads
what is a power stroke
a ‘nod’ of the myosin head that applies force to the actin filament via the cross bridge
