Muscle anatomy and physiology Flashcards
what is the order of structures in a muscle
whole muscle –> fascile –> fibre –> myofibril –> sarcomere
what is the difference between the epimysium, perimysium, and endomysium
epimysium = surrounds muscle
perimysium = surrounds fascicles
endomysium = surrounds fibres
what is a fusiform muscle
almost parallel fibres to the line of action
ex: biceps brachii
what is a unipennate muscle
one pennation angle
fascicles stick in to aponeuroses on the side
ex: medial gastroc
what is a bipennate muscle
two pennation angles
have internal aponeurosis/tendon (connection point) where the fascicles connect
ex: tibialis anterior
what is the difference between pennation angle and line of action
pennation angle = angle at which the fibres are oriented to the muscles line of action
line of action = line drawn between each tendon, axes at which the muscle would contract along
what parts of the muscle stay the same or change during contraction
stay the same = muscle volume
change (depends) = thickness, length, width, pennation
what is an aponeurosis
continuation of distal and proximal tendons
like a sheath over the muscle
collagen fibrils more randomly arranged than in tendon (in longitudinal direction)
results in greater longitudinal stiffness
where do the aponeuroses come from in the medial gastroc
deep aponeurosis = continuation of distal / achilles tendon
superficial aponeurosis = continuation of proximal tendon
how does the aponeurosis behave
heterogenous behaviour during contraction
can see changes and stretching in all directions
different regions behave differently
how are forces applied to the aponeurosis different
more complex and multidirectional
results in multidirectional deformations / strains
what is a muscle fibre defined as
single cell that is formed during development from the fusion of several undifferentiated immature cells (myoblasts)
what is the ECM in muscle
includes endo, peri, and epimysium
collagen is the major structural protein in ECM
- accounts for ~10% of muscle dry weight
what is the effect of ECM on the function of muscle
lot stiffer than fibres so overall stiffness of fibre bundles / fascicles is much higher
muscle is much stiffer when the connective tissue is present
what are myofibrils
composed of repeating units of sarcomeres which give them a characteristic striation pattern
(striated muscle)
what is the smallest functional unit of muscle
sarcomeres
what are the Z lines in muscle
defines outer bounds of each sarcomere
attachment of actin / thin filaments
appears as dark lines on electron micrograph
what is the A band
length of myosin / thick filament
has overlap with actin filaments
referred to as anisotropic band due to how it polarises light under an electron micrograph
what is the I band
region of only actin filaments
referred to as isotropic band due to how it does not polarise light
(no directional dependence in filtering)
what is the M line
where myosin tails connect (mid line)
what is the H zone
where only myosin is present
what are the different types of proteins in sarcomeres
actin / myosin (66% of myofilament proteins)
troponin / tropomyosin
titin
^^ 85% of total protein amount
nebulin and alpha actinin
myomesin and c-protein
what is the difference between troponin and tropomyosin
troponin = complex of 3 regulatory proteins (I, C, T)
tropomyosin = scaffold that maintains alignment and structure of thin filaments
both = involved in cross bridging
what is the function of titin
largest protein found
structural protein
links thick filaments to Z disc
what do nebulin and alpha actinin do
orient actin
what do myomesin and c-protein do
keeps tails of myosin filaments aligned
