Muscle Mechanics Flashcards
1
Q
isometric contractions
A
- do no work and have no power
- tension rises and falls with time, no flat top
- still use ATP
- maintaining posture
- stretching of series elastic elements (tendon) offsets contractile element contraction- load doesn’t move
2
Q
work
A
-force x distance
3
Q
power
A
work per unit time
4
Q
body movements
A
- require both isometric and isotonic conditions
- bicep lifts something with isotonic contraction
- back muscle undergoes isometric contraction
5
Q
isotonic contraction
A
- do all the work
- contract muscle until enough tension is generated to lift the load, then tension is constant until load is down again and muscle isometrically relaxes
- isometric contraction, isotonic contraction, isotonic relaxation, isometric relaxation
- isotonic means the muscle actually shortens
- greater load means higher plateau and greater time lag between stimulus and start of shortening
- contractile element shortens and series elastic element elongates until there is enough tension to lift load
6
Q
four stages of isotonic twitch
A
- isometric tension development
- isotonic shortening-contraction
- isotonic relaxation-elongation
- isometric relaxation
7
Q
velocity
A
-determined by initial increase in length vs time graph (because L=distance, v=d/t)
8
Q
rate of development of tension
A
-dF/dt
9
Q
isotonic twitch as a function of load
A
- with heavier load-
- longer delay until shortening (latent period increases)
- initial velocity decrease
- distance of shortening decreases
- muscle drops weight sooner (duration decreases)
10
Q
velocity vs load
A
- max velocity at 0 load
- there is an intermediate optimum
- no velocity at too heavy of a load
- distance shortened decreases with increase in load
11
Q
Po
A
- maximal isometric tension that can be generated at a given initial length and state of contractility
- function of number of force generating cross bridges- bigger muscle means more cross bridges and Po
- can increase in skeletal muscle with frequency modulation, recruitment of motor units and with initial length closer to optimal, not contractility
- in cardiac muscle, can increase with increased initial length and increased contractility but not recruitment
12
Q
maximum work and power
A
-intermediate loads
13
Q
pre load and afterload
A
- pre load of 1 g causes isotonic contraction, length shortens
- adding afterload for a total of 3 causes first isometric contraction to generate force from 1g to 3, then isotonic contraction, but shortening distance is less that pre load
14
Q
preload
A
- load required to stretch muscle from resting length
- some load needed to get into operating range
15
Q
afteroad
A
-total tension
