0512 - Muscle Force Production - EG Flashcards
Define a twitch.
a brief contractile response elicited by a single action potential.
Define a contraction.
development of force with or without shortening of muscle.
What are the two CNS mechanisms that produce force?
tetany and motor-unit recruitment
What is tetanus?
when individual twitches are no longer distinguishable from each other; temporal summation due to repeated APs that are more frequent than Ca2+ removal.
What is motor unit recruitment?
also known as spatial summation, the recruitment of more motor units, hence activating more muscle fibres and increasing force.
What are the two predominant types of muscle contraction?
Isometric - where there is no length change but force is produced.
Isotonic - where there is length change (shortening/concentric or lengthening/eccentric) against a constant force.
What type of muscle contraction occurs with minimal load upon muscle fibres? Maximum load? What would the velocity of muscle contraction be under each of these conditions?
Minimum load results in isotonic contraction with maximal velocity.
Maximum load results in isometric contraction, (zero velocity).
Define power.
the rate of work done (work per unit time)
= F x V
hence the same power can be produced by moving a lighter load quicker or a heavier load slower.
Define work.
force x distance per unit time
What are sources of energy for skeletal muscle?
creatine phosphate glycogen glucose fatty acids and triglycerides myoglobin
Define torque.
a twisting force
units: Nm
= force (N) x radius (m)
Define force.
N
mass x acceleration
When is muscle power output optimal?
around 1/3 of maximal force production, evaluated by a force-velocity relationship that determines power output under isotonic contraction conditions.
