BIOD43H3 Lecture Notes - Lecture 4: Maximum Force, Escape Response, Sarcomere
First quiz will be on next wednesday!!!
Slide 4:
In a red muscle, it shortens and lengthens at maximum length
When a muscle contracts ⅓ @ maximum velocity it produces maximum force/work
→ Muscle can produce reasonable amount of force when it shortens @ that velocity, velocity
is fast enough to produce maximum amount of work
For power velocity relationship:
Remember the ⅓ velocity relationship, going to where muscle produces maximum force, it is
doing isometric contraction.
Isometric contraction → Produces 0 work despite the force as 0 length change → power
production is 0
Maximum shortening velocity → unloaded muscle a muscle that is allowed to shorten as
much as it likes → Get length change, but work is 0, as 0 force is produced during shortening
cycle.
A fish that is using only red muscle, the relative length and strength is @ the area where you
get maximum efficiency.
→ For escape response, fish would use both white muscle and red muscle
→ Red fiber is first to be recruited (input from higher nervous) now recruiting both red and
white fibers.
→ Red muscle isn’t @ its optimum power (but notice white muscle fibers are
shortening @ range corresponding on sarcomere overlap of best power/force
productions.
Contraction velocity is very high (5 length changes/sec) relative to the when the fish is just
cruising.
Slide 5
There is another factor dictates how we operate white muscle fibers.
White muscle produces MAXIMUM power output → Escape response, efficiency doesn’t
matter as you need to escape danger.
Slide 6
Rate of nrg shows different relation.
Rate of nrg vs velocity of shortening muscle per cycle, which goes up and levels off
You produce most power @ 40% of maximum shortening velocity
find more resources at oneclass.com
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Document Summary
In a red muscle, it shortens and lengthens at maximum length. When a muscle contracts @ maximum velocity it produces maximum force/work. Muscle can produce reasonable amount of force when it shortens @ that velocity, velocity is fast enough to produce maximum amount of work. Remember the velocity relationship, going to where muscle produces maximum force, it is doing isometric contraction. Isometric contraction produces 0 work despite the force as 0 length change power production is 0. Maximum shortening velocity unloaded muscle a muscle that is allowed to shorten as much as it likes get length change, but work is 0, as 0 force is produced during shortening cycle. A fish that is using only red muscle, the relative length and strength is @ the area where you get maximum efficiency. For escape response, fish would use both white muscle and red muscle.
