Part 2: Biophysics of Muscle Contraction Flashcards
What increases muscle strength?
- Work = the displacement of load.
- Strength is a function of size; larger muscle = more strength.
- Muscle contraction without sufficient work does not increase strength.
Afterload:
the thing you want to move.
Preload:
- the ability of the muscles to displace a load (contractile force/strength). if the preload if larger than the afterload, displacement will occur.
When will displacement occur?
preload > afterload
Isometric contraction:
- no displacement, no work, no velocity.
- when afterload > preload.
Isotonic contraction:
- displacement occurs.
- preload > afterload.
What is the preload and afterload in the heart?
- Preload: Myocardial contractile force (left ventricle)
- Afterload: Blood pressure (“the weight”)
Preload > afterload in order for
displacement to occur.
Systole:
anytime a chamber in the heart contracts
Muscle twitches summate to form:
- a fused tetanus which causes muscle contraction to occur.
The three types of muscle tension:
- passive tension
- active tension
- total tension (active + passive)
Passive muscle tension is due to:
- elastic properties of muscle: muscle acting like a rubber-band like structure.
Passive tension increases as:
muscle is stretched.
Passive tension decreases as:
muscle is relaxed.
Active muscle tension is:
- everything that happens as you contract a muscle.
- decreases as muscle contracts, and eventually hits zero because actin and myosin run out of room.
Active muscle tension decreases as:
muscle contracts
Maximum tension is the maximum force of a muscle. It occurs at:
the start of contraction.
Power =
- P = Fv
- P = F (ΔX/ΔT)
Relationship between load and velocity of muscle fiber contraction:
- as load increases, velocity of muscle fiber contraction decreases
Relationship between the resting length of a muscle and power:
- as resting length increases, power increases
