PHYS20008 Lecture Notes - Lecture 11: Rigor Mortis, Petri Dish, Myosin Head
12 Jun 2018
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Lecture 11
PHYS20008 - HUMAN PHYSIOLOGY
LECTURE 11
SKELETAL MUSCLE (2)
•Does fatigue result from a loss of available ATP?
•No. If fatigue was a lack of ATP, we would go completely rigid.
CROSS BRIDGE CYCLE: A CONTRACTION?
•Myosin head is bound to actin filament until ATP comes in and allows myosin head to release
from actin filament. ATP is highly buffered in our body, so the stage of it being latched onto the
actin filament is very brief. When we die, our ATP stores break down, which ends up locking us
in the state where the myosin head is cross linked to the actin filament, so the muscles are locked
in place, causing rigor mortis.
•Cross bridge cycle occurs to ratchet and draw filaments closer together.
CONTRACTION
A SIMPLE MODEL FOR ISOMETRIC
CONTRACTION
•Iso = the same. (isotonic)
•Metric = length
•We are contracting muscle, exerting force,
but length isn’t changing.
•Force is pulling the muscle in one
direction, the cross bridges attempt to pull
it back in the other direction, so we have
no change in muscle length. Builds muscle.
•First phase of lifting something is
isometric.
CONCENTRIC CONTRACTION
•Mimetic or isotonic contraction
FORCE VELOCITY RELATIONSHIP
•A very light object doesn’t require much
force to be exerted and it can be lifted
with a very high velocity.
•At a molecular level: actin and myosin
interacting. They would end up orienting
themselves and start cross bridge cycling
if left in a petri dish together.
•If we put tension on either side then the
job is difficult and it canto work as
quickly and the more slowly !
!
it’s able to move through the cycle.
Document Summary
Skeletal muscle (2: does fatigue result from a loss of available atp, no. If fatigue was a lack of atp, we would go completely rigid. Cross bridge cycle: a contraction: myosin head is bound to actin filament until atp comes in and allows myosin head to release from actin filament. Atp is highly buffered in our body, so the stage of it being latched onto the actin filament is very brief. Builds muscle: first phase of lifting something is isometric. Force velocity relationship: a very light object doesn"t require much force to be exerted and it can be lifted with a very high velocity, at a molecular level: actin and myosin interacting. What happens next: the muscle has been contracted, what happens if we take the platform away, we can"t tell. Eccentric contraction: when the weight is more than the force. Force is still being exerted but the muscle is lengthened (like at the gym)
