Questions for Length-Tension Flashcards
To solidify the basic factors that determine cardiac muscle performance.
The three factors that determine the performance of isolated cardiac muscle are ______________________.
Preload, afterload and contractility
At the molecular level, preload refers to the _______________________________.
Amount of overlap of the actin-myosin complex.
At the sarcomere level, preload is indicated by the distance between __________________.
Z bands
Afterload is the load on the isolated muscle as it ____________________.
shortens
Contractility reflects the ____________________________ of the actin-myosin interactions.
Rate of turnover
Two things that determine contractility are the _________________________________.
Peak intracellular Ca++ concentration and the affinity of tropomyosin C for binding Ca++.
Until the muscle generates enough tension to equal or exceed the afterload, the contraction is ______________________.
Isometric
The total tension exerted by a contracting muscle has two components: __________________________________.
Passive elastic recoil and actively generated tension
An activated muscle shortens when the tension __________________________.
Exceeds the afterload
A change in contractility at a given preload will change the ______________________ component of tension but not the ___________________ component.
Active, passive recoil
The peak tension developed by a muscle when the afterload is infinite is determined by two things: the ______________________________________.
contractility and the preload
The amount of shortening that a muscle can perform at a given preload is determined by two things: the ___________________________.
afterload and the contractility
The _________________ tension curve separates the permissible from the prohibited range of operation on the length-tension plot.
total
Starling’s Law says that the energy available during a contraction depends upon the _____________________________.
initial muscle length
For a given preload and contractility, an increase in afterload will ______________________ the amount of shortening that can be done by the muscle.
decrease
The force in a muscle, active or passive, divided by the cross-sectional area of the muscle is called ____________________.
fiber stress
For a muscle shortening from a given preload with a given afterload, an increase in contractility would ______________________ the amount of shortening.
Increase
The metabolic cost of contractions under simlar preload and afterload conditions varies _____________________with the contractility of the muscle.
directly
Muscle contraction differs from muscle shortening in that the former does not necessarily involve a reduction in muscle __________________.
length
For a given preload and afterload, a decrease in contractility will _____________________ the amount of shortening that can be done.
decrease
The decay in muscle tension after being activated is due to the ________________________________.
decrease in cytosolic [Ca++]
