|What would happen if a skeletal muscle cell were
|Question Date: 2007-09-13|
Great question, and very relevant for a lot of
people! Cell damage can occur in lots of ways, and
the type of damage often will dictate "what
happens next."Let's say that there is some kind of
trauma to the muscle, such as a cut or crush. If
cells actually break open, this is something
called necrosis, and it leads to an immune
response - the body's surveillance system detects
the cell"parts" and essentially cleans up the
mess. This is part of a wound healing response.
There will be generation of new muscle cells, but
if the wound is large or the person is compromise
in other ways, there can be scarring. There are
other ways that cells can become damaged, and this
has to do with nutrient and oxygen availability.
In mammals, including humans, cells harvest energy
from glucose, and they can do it under aerobic
(with oxygen) or anaerobic (no or little oxygen)
conditions. Skeletal muscle, made up of fast and
slow twitch muscle fibers can function under
anaerobic conditions y using lactic acid
fermentation, but this can become a problem after
a while - it lowers the pH of the cell, which
eventually shuts down the cell (and is the cause
of cramping). Too long without oxygen, and the
Muscle cells, like most cells in the body, can
repair some kinds of mild, internal damage.It
depends on the type of damage and how severe it
is. Things like small holes in the cell wall, or
a single broken DNA strand, can often be repaired.
If the damage is too severe, a process called
apoptosis kicks in and destroys the cell from
inside before it can harm its neighbors.
Apoptosis is why you shed some outer skin after a
One unusual thing about muscle
cells is that if you work the muscles very hard,
like lifting weights, you actually cause
microscopic tears *between* cells--although not
inside a cell. The body responds by adding more
muscle cells, so the muscle gets bigger and
stronger. But large tears like a "pulled muscle"
are bad. They can trigger apoptosis (and other
effects) in the damaged muscle cells, which will
make the muscle weaker and leave scar tissue
Skeletal muscle cells are like nerve cells
(neurons): once they are made during the initial
stages of development, they never reproduce again.
So you have a fixed number of muscle cells in
your body, and if one dies, it is not replaced.
However, individual muscle cells can grow and
shrink by increasing or decreasing the number of
muscle fibers they contain. So if a muscle cell
dies, its neighbors could expand to fill the space
(and take on the workload). This expansion and
contraction is also the way we build (or lose)
muscles. Bodybuilders don't have any more muscle
cells than you or I do, but their individual
muscle cells contain many more fibers per
I should also mention that if a
muscle cell is damaged but not killed, it may be
able to repair itself by creating new proteins (or
other cell component parts) to replace the ones
that were damaged.
Thanks for asking a
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