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Re: [Re: dinosaur steaks and muscle fiber types]



Nothing.  Red fibers are fast twitch for bursts of speed (like on cats) and
white fibers are for endurance (like bird breasts).  {if white is slow
twitch it isn't so slow on hummingbird's or is their breast muscle red
muscle?}  There's also cardiac and smooth muscle fibers.

Michael Teuton



Just a quick physiology lesson:

1. Red muscle has more mitochondria relative to white muscle. 
2. Red muscle has fewer myofibrils per muscle fiber relative to white muscle.

The mitochondria are the 'power house' of the cell i.e. they are responsible
for ATP production. To maximise and sustain production of ATP, the aerobic
pathway of the Krebs cycle is taken, i.e. the path requiring oxygen. This
allows a longer period of muscle use without muscle fatigue. Myoglobin
facilitates the unloading of oxygen from the haemoglobin, which is Fe based,
hence the red pigmentation. As oxygen is required, the cross-bridge cycling
occurs ar a slower rate, hence use for sustained activity e.g. the goldfish in
a bowl swimming in circles. (Or,in the case of birds which fly frequently
their breasts are red e.g. the pigeon).

Conversly, white muscle produces ATP by glycolysis (break down of glucose into
pyruvate). Oxygen is not required for muscle contraction, therefore the
cross-bridge cycling can occur at a comparitively faster rate - hence the term
'fast twitch fibres'. Lactic acid is one of the waste products and there is an
oxygen debt which results in muscle fatigue. This is why white muscle is for
burst activity e.g. escape responses (breasts of birds which fly infrequently
e.g. the battery hen and other domestic fowl)

Hope this helps clarify things.

Anita
:)

Reality is what refuses
to go away when I stop
believing in it.

- Philip K. Dick

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